diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 5868 |
1 files changed, 5868 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c new file mode 100644 index 000000000..b1bb6cb58 --- /dev/null +++ b/kernel/workqueue.c @@ -0,0 +1,5868 @@ +/* + * kernel/workqueue.c - generic async execution with shared worker pool + * + * Copyright (C) 2002 Ingo Molnar + * + * Derived from the taskqueue/keventd code by: + * David Woodhouse <dwmw2@infradead.org> + * Andrew Morton + * Kai Petzke <wpp@marie.physik.tu-berlin.de> + * Theodore Ts'o <tytso@mit.edu> + * + * Made to use alloc_percpu by Christoph Lameter. + * + * Copyright (C) 2010 SUSE Linux Products GmbH + * Copyright (C) 2010 Tejun Heo <tj@kernel.org> + * + * This is the generic async execution mechanism. Work items as are + * executed in process context. The worker pool is shared and + * automatically managed. There are two worker pools for each CPU (one for + * normal work items and the other for high priority ones) and some extra + * pools for workqueues which are not bound to any specific CPU - the + * number of these backing pools is dynamic. + * + * Please read Documentation/core-api/workqueue.rst for details. + */ + +#include <linux/export.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/init.h> +#include <linux/signal.h> +#include <linux/completion.h> +#include <linux/workqueue.h> +#include <linux/slab.h> +#include <linux/cpu.h> +#include <linux/notifier.h> +#include <linux/kthread.h> +#include <linux/hardirq.h> +#include <linux/mempolicy.h> +#include <linux/freezer.h> +#include <linux/debug_locks.h> +#include <linux/lockdep.h> +#include <linux/idr.h> +#include <linux/jhash.h> +#include <linux/hashtable.h> +#include <linux/rculist.h> +#include <linux/nodemask.h> +#include <linux/moduleparam.h> +#include <linux/uaccess.h> +#include <linux/sched/isolation.h> +#include <linux/nmi.h> +#include <linux/kvm_para.h> + +#include "workqueue_internal.h" + +enum { + /* + * worker_pool flags + * + * A bound pool is either associated or disassociated with its CPU. + * While associated (!DISASSOCIATED), all workers are bound to the + * CPU and none has %WORKER_UNBOUND set and concurrency management + * is in effect. + * + * While DISASSOCIATED, the cpu may be offline and all workers have + * %WORKER_UNBOUND set and concurrency management disabled, and may + * be executing on any CPU. The pool behaves as an unbound one. + * + * Note that DISASSOCIATED should be flipped only while holding + * wq_pool_attach_mutex to avoid changing binding state while + * worker_attach_to_pool() is in progress. + */ + POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */ + POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ + + /* worker flags */ + WORKER_DIE = 1 << 1, /* die die die */ + WORKER_IDLE = 1 << 2, /* is idle */ + WORKER_PREP = 1 << 3, /* preparing to run works */ + WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ + WORKER_UNBOUND = 1 << 7, /* worker is unbound */ + WORKER_REBOUND = 1 << 8, /* worker was rebound */ + + WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE | + WORKER_UNBOUND | WORKER_REBOUND, + + NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */ + + UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */ + BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ + + MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ + IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ + + MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, + /* call for help after 10ms + (min two ticks) */ + MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ + CREATE_COOLDOWN = HZ, /* time to breath after fail */ + + /* + * Rescue workers are used only on emergencies and shared by + * all cpus. Give MIN_NICE. + */ + RESCUER_NICE_LEVEL = MIN_NICE, + HIGHPRI_NICE_LEVEL = MIN_NICE, + + WQ_NAME_LEN = 24, +}; + +/* + * Structure fields follow one of the following exclusion rules. + * + * I: Modifiable by initialization/destruction paths and read-only for + * everyone else. + * + * P: Preemption protected. Disabling preemption is enough and should + * only be modified and accessed from the local cpu. + * + * L: pool->lock protected. Access with pool->lock held. + * + * X: During normal operation, modification requires pool->lock and should + * be done only from local cpu. Either disabling preemption on local + * cpu or grabbing pool->lock is enough for read access. If + * POOL_DISASSOCIATED is set, it's identical to L. + * + * A: wq_pool_attach_mutex protected. + * + * PL: wq_pool_mutex protected. + * + * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads. + * + * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads. + * + * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or + * sched-RCU for reads. + * + * WQ: wq->mutex protected. + * + * WR: wq->mutex protected for writes. Sched-RCU protected for reads. + * + * MD: wq_mayday_lock protected. + */ + +/* struct worker is defined in workqueue_internal.h */ + +struct worker_pool { + spinlock_t lock; /* the pool lock */ + int cpu; /* I: the associated cpu */ + int node; /* I: the associated node ID */ + int id; /* I: pool ID */ + unsigned int flags; /* X: flags */ + + unsigned long watchdog_ts; /* L: watchdog timestamp */ + + struct list_head worklist; /* L: list of pending works */ + + int nr_workers; /* L: total number of workers */ + int nr_idle; /* L: currently idle workers */ + + struct list_head idle_list; /* X: list of idle workers */ + struct timer_list idle_timer; /* L: worker idle timeout */ + struct timer_list mayday_timer; /* L: SOS timer for workers */ + + /* a workers is either on busy_hash or idle_list, or the manager */ + DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); + /* L: hash of busy workers */ + + struct worker *manager; /* L: purely informational */ + struct list_head workers; /* A: attached workers */ + struct completion *detach_completion; /* all workers detached */ + + struct ida worker_ida; /* worker IDs for task name */ + + struct workqueue_attrs *attrs; /* I: worker attributes */ + struct hlist_node hash_node; /* PL: unbound_pool_hash node */ + int refcnt; /* PL: refcnt for unbound pools */ + + /* + * The current concurrency level. As it's likely to be accessed + * from other CPUs during try_to_wake_up(), put it in a separate + * cacheline. + */ + atomic_t nr_running ____cacheline_aligned_in_smp; + + /* + * Destruction of pool is sched-RCU protected to allow dereferences + * from get_work_pool(). + */ + struct rcu_head rcu; +} ____cacheline_aligned_in_smp; + +/* + * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS + * of work_struct->data are used for flags and the remaining high bits + * point to the pwq; thus, pwqs need to be aligned at two's power of the + * number of flag bits. + */ +struct pool_workqueue { + struct worker_pool *pool; /* I: the associated pool */ + struct workqueue_struct *wq; /* I: the owning workqueue */ + int work_color; /* L: current color */ + int flush_color; /* L: flushing color */ + int refcnt; /* L: reference count */ + int nr_in_flight[WORK_NR_COLORS]; + /* L: nr of in_flight works */ + int nr_active; /* L: nr of active works */ + int max_active; /* L: max active works */ + struct list_head delayed_works; /* L: delayed works */ + struct list_head pwqs_node; /* WR: node on wq->pwqs */ + struct list_head mayday_node; /* MD: node on wq->maydays */ + + /* + * Release of unbound pwq is punted to system_wq. See put_pwq() + * and pwq_unbound_release_workfn() for details. pool_workqueue + * itself is also sched-RCU protected so that the first pwq can be + * determined without grabbing wq->mutex. + */ + struct work_struct unbound_release_work; + struct rcu_head rcu; +} __aligned(1 << WORK_STRUCT_FLAG_BITS); + +/* + * Structure used to wait for workqueue flush. + */ +struct wq_flusher { + struct list_head list; /* WQ: list of flushers */ + int flush_color; /* WQ: flush color waiting for */ + struct completion done; /* flush completion */ +}; + +struct wq_device; + +/* + * The externally visible workqueue. It relays the issued work items to + * the appropriate worker_pool through its pool_workqueues. + */ +struct workqueue_struct { + struct list_head pwqs; /* WR: all pwqs of this wq */ + struct list_head list; /* PR: list of all workqueues */ + + struct mutex mutex; /* protects this wq */ + int work_color; /* WQ: current work color */ + int flush_color; /* WQ: current flush color */ + atomic_t nr_pwqs_to_flush; /* flush in progress */ + struct wq_flusher *first_flusher; /* WQ: first flusher */ + struct list_head flusher_queue; /* WQ: flush waiters */ + struct list_head flusher_overflow; /* WQ: flush overflow list */ + + struct list_head maydays; /* MD: pwqs requesting rescue */ + struct worker *rescuer; /* I: rescue worker */ + + int nr_drainers; /* WQ: drain in progress */ + int saved_max_active; /* WQ: saved pwq max_active */ + + struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */ + struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */ + +#ifdef CONFIG_SYSFS + struct wq_device *wq_dev; /* I: for sysfs interface */ +#endif +#ifdef CONFIG_LOCKDEP + struct lockdep_map lockdep_map; +#endif + char name[WQ_NAME_LEN]; /* I: workqueue name */ + + /* + * Destruction of workqueue_struct is sched-RCU protected to allow + * walking the workqueues list without grabbing wq_pool_mutex. + * This is used to dump all workqueues from sysrq. + */ + struct rcu_head rcu; + + /* hot fields used during command issue, aligned to cacheline */ + unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */ + struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */ + struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */ +}; + +static struct kmem_cache *pwq_cache; + +static cpumask_var_t *wq_numa_possible_cpumask; + /* possible CPUs of each node */ + +static bool wq_disable_numa; +module_param_named(disable_numa, wq_disable_numa, bool, 0444); + +/* see the comment above the definition of WQ_POWER_EFFICIENT */ +static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT); +module_param_named(power_efficient, wq_power_efficient, bool, 0444); + +static bool wq_online; /* can kworkers be created yet? */ + +static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ + +/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */ +static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf; + +static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */ +static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */ +static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */ +static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */ + +static LIST_HEAD(workqueues); /* PR: list of all workqueues */ +static bool workqueue_freezing; /* PL: have wqs started freezing? */ + +/* PL: allowable cpus for unbound wqs and work items */ +static cpumask_var_t wq_unbound_cpumask; + +/* CPU where unbound work was last round robin scheduled from this CPU */ +static DEFINE_PER_CPU(int, wq_rr_cpu_last); + +/* + * Local execution of unbound work items is no longer guaranteed. The + * following always forces round-robin CPU selection on unbound work items + * to uncover usages which depend on it. + */ +#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU +static bool wq_debug_force_rr_cpu = true; +#else +static bool wq_debug_force_rr_cpu = false; +#endif +module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644); + +/* the per-cpu worker pools */ +static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools); + +static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */ + +/* PL: hash of all unbound pools keyed by pool->attrs */ +static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER); + +/* I: attributes used when instantiating standard unbound pools on demand */ +static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS]; + +/* I: attributes used when instantiating ordered pools on demand */ +static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS]; + +struct workqueue_struct *system_wq __read_mostly; +EXPORT_SYMBOL(system_wq); +struct workqueue_struct *system_highpri_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_highpri_wq); +struct workqueue_struct *system_long_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_long_wq); +struct workqueue_struct *system_unbound_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_unbound_wq); +struct workqueue_struct *system_freezable_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_freezable_wq); +struct workqueue_struct *system_power_efficient_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_power_efficient_wq); +struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq); + +static int worker_thread(void *__worker); +static void workqueue_sysfs_unregister(struct workqueue_struct *wq); + +#define CREATE_TRACE_POINTS +#include <trace/events/workqueue.h> + +#define assert_rcu_or_pool_mutex() \ + RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ + !lockdep_is_held(&wq_pool_mutex), \ + "sched RCU or wq_pool_mutex should be held") + +#define assert_rcu_or_wq_mutex(wq) \ + RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ + !lockdep_is_held(&wq->mutex), \ + "sched RCU or wq->mutex should be held") + +#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \ + RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ + !lockdep_is_held(&wq->mutex) && \ + !lockdep_is_held(&wq_pool_mutex), \ + "sched RCU, wq->mutex or wq_pool_mutex should be held") + +#define for_each_cpu_worker_pool(pool, cpu) \ + for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \ + (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \ + (pool)++) + +/** + * for_each_pool - iterate through all worker_pools in the system + * @pool: iteration cursor + * @pi: integer used for iteration + * + * This must be called either with wq_pool_mutex held or sched RCU read + * locked. If the pool needs to be used beyond the locking in effect, the + * caller is responsible for guaranteeing that the pool stays online. + * + * The if/else clause exists only for the lockdep assertion and can be + * ignored. + */ +#define for_each_pool(pool, pi) \ + idr_for_each_entry(&worker_pool_idr, pool, pi) \ + if (({ assert_rcu_or_pool_mutex(); false; })) { } \ + else + +/** + * for_each_pool_worker - iterate through all workers of a worker_pool + * @worker: iteration cursor + * @pool: worker_pool to iterate workers of + * + * This must be called with wq_pool_attach_mutex. + * + * The if/else clause exists only for the lockdep assertion and can be + * ignored. + */ +#define for_each_pool_worker(worker, pool) \ + list_for_each_entry((worker), &(pool)->workers, node) \ + if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \ + else + +/** + * for_each_pwq - iterate through all pool_workqueues of the specified workqueue + * @pwq: iteration cursor + * @wq: the target workqueue + * + * This must be called either with wq->mutex held or sched RCU read locked. + * If the pwq needs to be used beyond the locking in effect, the caller is + * responsible for guaranteeing that the pwq stays online. + * + * The if/else clause exists only for the lockdep assertion and can be + * ignored. + */ +#define for_each_pwq(pwq, wq) \ + list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \ + if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \ + else + +#ifdef CONFIG_DEBUG_OBJECTS_WORK + +static struct debug_obj_descr work_debug_descr; + +static void *work_debug_hint(void *addr) +{ + return ((struct work_struct *) addr)->func; +} + +static bool work_is_static_object(void *addr) +{ + struct work_struct *work = addr; + + return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work)); +} + +/* + * fixup_init is called when: + * - an active object is initialized + */ +static bool work_fixup_init(void *addr, enum debug_obj_state state) +{ + struct work_struct *work = addr; + + switch (state) { + case ODEBUG_STATE_ACTIVE: + cancel_work_sync(work); + debug_object_init(work, &work_debug_descr); + return true; + default: + return false; + } +} + +/* + * fixup_free is called when: + * - an active object is freed + */ +static bool work_fixup_free(void *addr, enum debug_obj_state state) +{ + struct work_struct *work = addr; + + switch (state) { + case ODEBUG_STATE_ACTIVE: + cancel_work_sync(work); + debug_object_free(work, &work_debug_descr); + return true; + default: + return false; + } +} + +static struct debug_obj_descr work_debug_descr = { + .name = "work_struct", + .debug_hint = work_debug_hint, + .is_static_object = work_is_static_object, + .fixup_init = work_fixup_init, + .fixup_free = work_fixup_free, +}; + +static inline void debug_work_activate(struct work_struct *work) +{ + debug_object_activate(work, &work_debug_descr); +} + +static inline void debug_work_deactivate(struct work_struct *work) +{ + debug_object_deactivate(work, &work_debug_descr); +} + +void __init_work(struct work_struct *work, int onstack) +{ + if (onstack) + debug_object_init_on_stack(work, &work_debug_descr); + else + debug_object_init(work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(__init_work); + +void destroy_work_on_stack(struct work_struct *work) +{ + debug_object_free(work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_work_on_stack); + +void destroy_delayed_work_on_stack(struct delayed_work *work) +{ + destroy_timer_on_stack(&work->timer); + debug_object_free(&work->work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack); + +#else +static inline void debug_work_activate(struct work_struct *work) { } +static inline void debug_work_deactivate(struct work_struct *work) { } +#endif + +/** + * worker_pool_assign_id - allocate ID and assing it to @pool + * @pool: the pool pointer of interest + * + * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned + * successfully, -errno on failure. + */ +static int worker_pool_assign_id(struct worker_pool *pool) +{ + int ret; + + lockdep_assert_held(&wq_pool_mutex); + + ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE, + GFP_KERNEL); + if (ret >= 0) { + pool->id = ret; + return 0; + } + return ret; +} + +/** + * unbound_pwq_by_node - return the unbound pool_workqueue for the given node + * @wq: the target workqueue + * @node: the node ID + * + * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU + * read locked. + * If the pwq needs to be used beyond the locking in effect, the caller is + * responsible for guaranteeing that the pwq stays online. + * + * Return: The unbound pool_workqueue for @node. + */ +static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq, + int node) +{ + assert_rcu_or_wq_mutex_or_pool_mutex(wq); + + /* + * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a + * delayed item is pending. The plan is to keep CPU -> NODE + * mapping valid and stable across CPU on/offlines. Once that + * happens, this workaround can be removed. + */ + if (unlikely(node == NUMA_NO_NODE)) + return wq->dfl_pwq; + + return rcu_dereference_raw(wq->numa_pwq_tbl[node]); +} + +static unsigned int work_color_to_flags(int color) +{ + return color << WORK_STRUCT_COLOR_SHIFT; +} + +static int get_work_color(struct work_struct *work) +{ + return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & + ((1 << WORK_STRUCT_COLOR_BITS) - 1); +} + +static int work_next_color(int color) +{ + return (color + 1) % WORK_NR_COLORS; +} + +/* + * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data + * contain the pointer to the queued pwq. Once execution starts, the flag + * is cleared and the high bits contain OFFQ flags and pool ID. + * + * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling() + * and clear_work_data() can be used to set the pwq, pool or clear + * work->data. These functions should only be called while the work is + * owned - ie. while the PENDING bit is set. + * + * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq + * corresponding to a work. Pool is available once the work has been + * queued anywhere after initialization until it is sync canceled. pwq is + * available only while the work item is queued. + * + * %WORK_OFFQ_CANCELING is used to mark a work item which is being + * canceled. While being canceled, a work item may have its PENDING set + * but stay off timer and worklist for arbitrarily long and nobody should + * try to steal the PENDING bit. + */ +static inline void set_work_data(struct work_struct *work, unsigned long data, + unsigned long flags) +{ + WARN_ON_ONCE(!work_pending(work)); + atomic_long_set(&work->data, data | flags | work_static(work)); +} + +static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq, + unsigned long extra_flags) +{ + set_work_data(work, (unsigned long)pwq, + WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags); +} + +static void set_work_pool_and_keep_pending(struct work_struct *work, + int pool_id) +{ + set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, + WORK_STRUCT_PENDING); +} + +static void set_work_pool_and_clear_pending(struct work_struct *work, + int pool_id) +{ + /* + * The following wmb is paired with the implied mb in + * test_and_set_bit(PENDING) and ensures all updates to @work made + * here are visible to and precede any updates by the next PENDING + * owner. + */ + smp_wmb(); + set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0); + /* + * The following mb guarantees that previous clear of a PENDING bit + * will not be reordered with any speculative LOADS or STORES from + * work->current_func, which is executed afterwards. This possible + * reordering can lead to a missed execution on attempt to qeueue + * the same @work. E.g. consider this case: + * + * CPU#0 CPU#1 + * ---------------------------- -------------------------------- + * + * 1 STORE event_indicated + * 2 queue_work_on() { + * 3 test_and_set_bit(PENDING) + * 4 } set_..._and_clear_pending() { + * 5 set_work_data() # clear bit + * 6 smp_mb() + * 7 work->current_func() { + * 8 LOAD event_indicated + * } + * + * Without an explicit full barrier speculative LOAD on line 8 can + * be executed before CPU#0 does STORE on line 1. If that happens, + * CPU#0 observes the PENDING bit is still set and new execution of + * a @work is not queued in a hope, that CPU#1 will eventually + * finish the queued @work. Meanwhile CPU#1 does not see + * event_indicated is set, because speculative LOAD was executed + * before actual STORE. + */ + smp_mb(); +} + +static void clear_work_data(struct work_struct *work) +{ + smp_wmb(); /* see set_work_pool_and_clear_pending() */ + set_work_data(work, WORK_STRUCT_NO_POOL, 0); +} + +static struct pool_workqueue *get_work_pwq(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + + if (data & WORK_STRUCT_PWQ) + return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); + else + return NULL; +} + +/** + * get_work_pool - return the worker_pool a given work was associated with + * @work: the work item of interest + * + * Pools are created and destroyed under wq_pool_mutex, and allows read + * access under sched-RCU read lock. As such, this function should be + * called under wq_pool_mutex or with preemption disabled. + * + * All fields of the returned pool are accessible as long as the above + * mentioned locking is in effect. If the returned pool needs to be used + * beyond the critical section, the caller is responsible for ensuring the + * returned pool is and stays online. + * + * Return: The worker_pool @work was last associated with. %NULL if none. + */ +static struct worker_pool *get_work_pool(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + int pool_id; + + assert_rcu_or_pool_mutex(); + + if (data & WORK_STRUCT_PWQ) + return ((struct pool_workqueue *) + (data & WORK_STRUCT_WQ_DATA_MASK))->pool; + + pool_id = data >> WORK_OFFQ_POOL_SHIFT; + if (pool_id == WORK_OFFQ_POOL_NONE) + return NULL; + + return idr_find(&worker_pool_idr, pool_id); +} + +/** + * get_work_pool_id - return the worker pool ID a given work is associated with + * @work: the work item of interest + * + * Return: The worker_pool ID @work was last associated with. + * %WORK_OFFQ_POOL_NONE if none. + */ +static int get_work_pool_id(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + + if (data & WORK_STRUCT_PWQ) + return ((struct pool_workqueue *) + (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id; + + return data >> WORK_OFFQ_POOL_SHIFT; +} + +static void mark_work_canceling(struct work_struct *work) +{ + unsigned long pool_id = get_work_pool_id(work); + + pool_id <<= WORK_OFFQ_POOL_SHIFT; + set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING); +} + +static bool work_is_canceling(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + + return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING); +} + +/* + * Policy functions. These define the policies on how the global worker + * pools are managed. Unless noted otherwise, these functions assume that + * they're being called with pool->lock held. + */ + +static bool __need_more_worker(struct worker_pool *pool) +{ + return !atomic_read(&pool->nr_running); +} + +/* + * Need to wake up a worker? Called from anything but currently + * running workers. + * + * Note that, because unbound workers never contribute to nr_running, this + * function will always return %true for unbound pools as long as the + * worklist isn't empty. + */ +static bool need_more_worker(struct worker_pool *pool) +{ + return !list_empty(&pool->worklist) && __need_more_worker(pool); +} + +/* Can I start working? Called from busy but !running workers. */ +static bool may_start_working(struct worker_pool *pool) +{ + return pool->nr_idle; +} + +/* Do I need to keep working? Called from currently running workers. */ +static bool keep_working(struct worker_pool *pool) +{ + return !list_empty(&pool->worklist) && + atomic_read(&pool->nr_running) <= 1; +} + +/* Do we need a new worker? Called from manager. */ +static bool need_to_create_worker(struct worker_pool *pool) +{ + return need_more_worker(pool) && !may_start_working(pool); +} + +/* Do we have too many workers and should some go away? */ +static bool too_many_workers(struct worker_pool *pool) +{ + bool managing = pool->flags & POOL_MANAGER_ACTIVE; + int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ + int nr_busy = pool->nr_workers - nr_idle; + + return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; +} + +/* + * Wake up functions. + */ + +/* Return the first idle worker. Safe with preemption disabled */ +static struct worker *first_idle_worker(struct worker_pool *pool) +{ + if (unlikely(list_empty(&pool->idle_list))) + return NULL; + + return list_first_entry(&pool->idle_list, struct worker, entry); +} + +/** + * wake_up_worker - wake up an idle worker + * @pool: worker pool to wake worker from + * + * Wake up the first idle worker of @pool. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void wake_up_worker(struct worker_pool *pool) +{ + struct worker *worker = first_idle_worker(pool); + + if (likely(worker)) + wake_up_process(worker->task); +} + +/** + * wq_worker_waking_up - a worker is waking up + * @task: task waking up + * @cpu: CPU @task is waking up to + * + * This function is called during try_to_wake_up() when a worker is + * being awoken. + * + * CONTEXT: + * spin_lock_irq(rq->lock) + */ +void wq_worker_waking_up(struct task_struct *task, int cpu) +{ + struct worker *worker = kthread_data(task); + + if (!(worker->flags & WORKER_NOT_RUNNING)) { + WARN_ON_ONCE(worker->pool->cpu != cpu); + atomic_inc(&worker->pool->nr_running); + } +} + +/** + * wq_worker_sleeping - a worker is going to sleep + * @task: task going to sleep + * + * This function is called during schedule() when a busy worker is + * going to sleep. Worker on the same cpu can be woken up by + * returning pointer to its task. + * + * CONTEXT: + * spin_lock_irq(rq->lock) + * + * Return: + * Worker task on @cpu to wake up, %NULL if none. + */ +struct task_struct *wq_worker_sleeping(struct task_struct *task) +{ + struct worker *worker = kthread_data(task), *to_wakeup = NULL; + struct worker_pool *pool; + + /* + * Rescuers, which may not have all the fields set up like normal + * workers, also reach here, let's not access anything before + * checking NOT_RUNNING. + */ + if (worker->flags & WORKER_NOT_RUNNING) + return NULL; + + pool = worker->pool; + + /* this can only happen on the local cpu */ + if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id())) + return NULL; + + /* + * The counterpart of the following dec_and_test, implied mb, + * worklist not empty test sequence is in insert_work(). + * Please read comment there. + * + * NOT_RUNNING is clear. This means that we're bound to and + * running on the local cpu w/ rq lock held and preemption + * disabled, which in turn means that none else could be + * manipulating idle_list, so dereferencing idle_list without pool + * lock is safe. + */ + if (atomic_dec_and_test(&pool->nr_running) && + !list_empty(&pool->worklist)) + to_wakeup = first_idle_worker(pool); + return to_wakeup ? to_wakeup->task : NULL; +} + +/** + * worker_set_flags - set worker flags and adjust nr_running accordingly + * @worker: self + * @flags: flags to set + * + * Set @flags in @worker->flags and adjust nr_running accordingly. + * + * CONTEXT: + * spin_lock_irq(pool->lock) + */ +static inline void worker_set_flags(struct worker *worker, unsigned int flags) +{ + struct worker_pool *pool = worker->pool; + + WARN_ON_ONCE(worker->task != current); + + /* If transitioning into NOT_RUNNING, adjust nr_running. */ + if ((flags & WORKER_NOT_RUNNING) && + !(worker->flags & WORKER_NOT_RUNNING)) { + atomic_dec(&pool->nr_running); + } + + worker->flags |= flags; +} + +/** + * worker_clr_flags - clear worker flags and adjust nr_running accordingly + * @worker: self + * @flags: flags to clear + * + * Clear @flags in @worker->flags and adjust nr_running accordingly. + * + * CONTEXT: + * spin_lock_irq(pool->lock) + */ +static inline void worker_clr_flags(struct worker *worker, unsigned int flags) +{ + struct worker_pool *pool = worker->pool; + unsigned int oflags = worker->flags; + + WARN_ON_ONCE(worker->task != current); + + worker->flags &= ~flags; + + /* + * If transitioning out of NOT_RUNNING, increment nr_running. Note + * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask + * of multiple flags, not a single flag. + */ + if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) + if (!(worker->flags & WORKER_NOT_RUNNING)) + atomic_inc(&pool->nr_running); +} + +/** + * find_worker_executing_work - find worker which is executing a work + * @pool: pool of interest + * @work: work to find worker for + * + * Find a worker which is executing @work on @pool by searching + * @pool->busy_hash which is keyed by the address of @work. For a worker + * to match, its current execution should match the address of @work and + * its work function. This is to avoid unwanted dependency between + * unrelated work executions through a work item being recycled while still + * being executed. + * + * This is a bit tricky. A work item may be freed once its execution + * starts and nothing prevents the freed area from being recycled for + * another work item. If the same work item address ends up being reused + * before the original execution finishes, workqueue will identify the + * recycled work item as currently executing and make it wait until the + * current execution finishes, introducing an unwanted dependency. + * + * This function checks the work item address and work function to avoid + * false positives. Note that this isn't complete as one may construct a + * work function which can introduce dependency onto itself through a + * recycled work item. Well, if somebody wants to shoot oneself in the + * foot that badly, there's only so much we can do, and if such deadlock + * actually occurs, it should be easy to locate the culprit work function. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + * + * Return: + * Pointer to worker which is executing @work if found, %NULL + * otherwise. + */ +static struct worker *find_worker_executing_work(struct worker_pool *pool, + struct work_struct *work) +{ + struct worker *worker; + + hash_for_each_possible(pool->busy_hash, worker, hentry, + (unsigned long)work) + if (worker->current_work == work && + worker->current_func == work->func) + return worker; + + return NULL; +} + +/** + * move_linked_works - move linked works to a list + * @work: start of series of works to be scheduled + * @head: target list to append @work to + * @nextp: out parameter for nested worklist walking + * + * Schedule linked works starting from @work to @head. Work series to + * be scheduled starts at @work and includes any consecutive work with + * WORK_STRUCT_LINKED set in its predecessor. + * + * If @nextp is not NULL, it's updated to point to the next work of + * the last scheduled work. This allows move_linked_works() to be + * nested inside outer list_for_each_entry_safe(). + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void move_linked_works(struct work_struct *work, struct list_head *head, + struct work_struct **nextp) +{ + struct work_struct *n; + + /* + * Linked worklist will always end before the end of the list, + * use NULL for list head. + */ + list_for_each_entry_safe_from(work, n, NULL, entry) { + list_move_tail(&work->entry, head); + if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) + break; + } + + /* + * If we're already inside safe list traversal and have moved + * multiple works to the scheduled queue, the next position + * needs to be updated. + */ + if (nextp) + *nextp = n; +} + +/** + * get_pwq - get an extra reference on the specified pool_workqueue + * @pwq: pool_workqueue to get + * + * Obtain an extra reference on @pwq. The caller should guarantee that + * @pwq has positive refcnt and be holding the matching pool->lock. + */ +static void get_pwq(struct pool_workqueue *pwq) +{ + lockdep_assert_held(&pwq->pool->lock); + WARN_ON_ONCE(pwq->refcnt <= 0); + pwq->refcnt++; +} + +/** + * put_pwq - put a pool_workqueue reference + * @pwq: pool_workqueue to put + * + * Drop a reference of @pwq. If its refcnt reaches zero, schedule its + * destruction. The caller should be holding the matching pool->lock. + */ +static void put_pwq(struct pool_workqueue *pwq) +{ + lockdep_assert_held(&pwq->pool->lock); + if (likely(--pwq->refcnt)) + return; + if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND))) + return; + /* + * @pwq can't be released under pool->lock, bounce to + * pwq_unbound_release_workfn(). This never recurses on the same + * pool->lock as this path is taken only for unbound workqueues and + * the release work item is scheduled on a per-cpu workqueue. To + * avoid lockdep warning, unbound pool->locks are given lockdep + * subclass of 1 in get_unbound_pool(). + */ + schedule_work(&pwq->unbound_release_work); +} + +/** + * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock + * @pwq: pool_workqueue to put (can be %NULL) + * + * put_pwq() with locking. This function also allows %NULL @pwq. + */ +static void put_pwq_unlocked(struct pool_workqueue *pwq) +{ + if (pwq) { + /* + * As both pwqs and pools are sched-RCU protected, the + * following lock operations are safe. + */ + spin_lock_irq(&pwq->pool->lock); + put_pwq(pwq); + spin_unlock_irq(&pwq->pool->lock); + } +} + +static void pwq_activate_delayed_work(struct work_struct *work) +{ + struct pool_workqueue *pwq = get_work_pwq(work); + + trace_workqueue_activate_work(work); + if (list_empty(&pwq->pool->worklist)) + pwq->pool->watchdog_ts = jiffies; + move_linked_works(work, &pwq->pool->worklist, NULL); + __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); + pwq->nr_active++; +} + +static void pwq_activate_first_delayed(struct pool_workqueue *pwq) +{ + struct work_struct *work = list_first_entry(&pwq->delayed_works, + struct work_struct, entry); + + pwq_activate_delayed_work(work); +} + +/** + * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight + * @pwq: pwq of interest + * @color: color of work which left the queue + * + * A work either has completed or is removed from pending queue, + * decrement nr_in_flight of its pwq and handle workqueue flushing. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color) +{ + /* uncolored work items don't participate in flushing or nr_active */ + if (color == WORK_NO_COLOR) + goto out_put; + + pwq->nr_in_flight[color]--; + + pwq->nr_active--; + if (!list_empty(&pwq->delayed_works)) { + /* one down, submit a delayed one */ + if (pwq->nr_active < pwq->max_active) + pwq_activate_first_delayed(pwq); + } + + /* is flush in progress and are we at the flushing tip? */ + if (likely(pwq->flush_color != color)) + goto out_put; + + /* are there still in-flight works? */ + if (pwq->nr_in_flight[color]) + goto out_put; + + /* this pwq is done, clear flush_color */ + pwq->flush_color = -1; + + /* + * If this was the last pwq, wake up the first flusher. It + * will handle the rest. + */ + if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush)) + complete(&pwq->wq->first_flusher->done); +out_put: + put_pwq(pwq); +} + +/** + * try_to_grab_pending - steal work item from worklist and disable irq + * @work: work item to steal + * @is_dwork: @work is a delayed_work + * @flags: place to store irq state + * + * Try to grab PENDING bit of @work. This function can handle @work in any + * stable state - idle, on timer or on worklist. + * + * Return: + * 1 if @work was pending and we successfully stole PENDING + * 0 if @work was idle and we claimed PENDING + * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry + * -ENOENT if someone else is canceling @work, this state may persist + * for arbitrarily long + * + * Note: + * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting + * interrupted while holding PENDING and @work off queue, irq must be + * disabled on entry. This, combined with delayed_work->timer being + * irqsafe, ensures that we return -EAGAIN for finite short period of time. + * + * On successful return, >= 0, irq is disabled and the caller is + * responsible for releasing it using local_irq_restore(*@flags). + * + * This function is safe to call from any context including IRQ handler. + */ +static int try_to_grab_pending(struct work_struct *work, bool is_dwork, + unsigned long *flags) +{ + struct worker_pool *pool; + struct pool_workqueue *pwq; + + local_irq_save(*flags); + + /* try to steal the timer if it exists */ + if (is_dwork) { + struct delayed_work *dwork = to_delayed_work(work); + + /* + * dwork->timer is irqsafe. If del_timer() fails, it's + * guaranteed that the timer is not queued anywhere and not + * running on the local CPU. + */ + if (likely(del_timer(&dwork->timer))) + return 1; + } + + /* try to claim PENDING the normal way */ + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) + return 0; + + /* + * The queueing is in progress, or it is already queued. Try to + * steal it from ->worklist without clearing WORK_STRUCT_PENDING. + */ + pool = get_work_pool(work); + if (!pool) + goto fail; + + spin_lock(&pool->lock); + /* + * work->data is guaranteed to point to pwq only while the work + * item is queued on pwq->wq, and both updating work->data to point + * to pwq on queueing and to pool on dequeueing are done under + * pwq->pool->lock. This in turn guarantees that, if work->data + * points to pwq which is associated with a locked pool, the work + * item is currently queued on that pool. + */ + pwq = get_work_pwq(work); + if (pwq && pwq->pool == pool) { + debug_work_deactivate(work); + + /* + * A delayed work item cannot be grabbed directly because + * it might have linked NO_COLOR work items which, if left + * on the delayed_list, will confuse pwq->nr_active + * management later on and cause stall. Make sure the work + * item is activated before grabbing. + */ + if (*work_data_bits(work) & WORK_STRUCT_DELAYED) + pwq_activate_delayed_work(work); + + list_del_init(&work->entry); + pwq_dec_nr_in_flight(pwq, get_work_color(work)); + + /* work->data points to pwq iff queued, point to pool */ + set_work_pool_and_keep_pending(work, pool->id); + + spin_unlock(&pool->lock); + return 1; + } + spin_unlock(&pool->lock); +fail: + local_irq_restore(*flags); + if (work_is_canceling(work)) + return -ENOENT; + cpu_relax(); + return -EAGAIN; +} + +/** + * insert_work - insert a work into a pool + * @pwq: pwq @work belongs to + * @work: work to insert + * @head: insertion point + * @extra_flags: extra WORK_STRUCT_* flags to set + * + * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to + * work_struct flags. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, + struct list_head *head, unsigned int extra_flags) +{ + struct worker_pool *pool = pwq->pool; + + /* we own @work, set data and link */ + set_work_pwq(work, pwq, extra_flags); + list_add_tail(&work->entry, head); + get_pwq(pwq); + + /* + * Ensure either wq_worker_sleeping() sees the above + * list_add_tail() or we see zero nr_running to avoid workers lying + * around lazily while there are works to be processed. + */ + smp_mb(); + + if (__need_more_worker(pool)) + wake_up_worker(pool); +} + +/* + * Test whether @work is being queued from another work executing on the + * same workqueue. + */ +static bool is_chained_work(struct workqueue_struct *wq) +{ + struct worker *worker; + + worker = current_wq_worker(); + /* + * Return %true iff I'm a worker execuing a work item on @wq. If + * I'm @worker, it's safe to dereference it without locking. + */ + return worker && worker->current_pwq->wq == wq; +} + +/* + * When queueing an unbound work item to a wq, prefer local CPU if allowed + * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to + * avoid perturbing sensitive tasks. + */ +static int wq_select_unbound_cpu(int cpu) +{ + static bool printed_dbg_warning; + int new_cpu; + + if (likely(!wq_debug_force_rr_cpu)) { + if (cpumask_test_cpu(cpu, wq_unbound_cpumask)) + return cpu; + } else if (!printed_dbg_warning) { + pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n"); + printed_dbg_warning = true; + } + + if (cpumask_empty(wq_unbound_cpumask)) + return cpu; + + new_cpu = __this_cpu_read(wq_rr_cpu_last); + new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask); + if (unlikely(new_cpu >= nr_cpu_ids)) { + new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask); + if (unlikely(new_cpu >= nr_cpu_ids)) + return cpu; + } + __this_cpu_write(wq_rr_cpu_last, new_cpu); + + return new_cpu; +} + +static void __queue_work(int cpu, struct workqueue_struct *wq, + struct work_struct *work) +{ + struct pool_workqueue *pwq; + struct worker_pool *last_pool; + struct list_head *worklist; + unsigned int work_flags; + unsigned int req_cpu = cpu; + + /* + * While a work item is PENDING && off queue, a task trying to + * steal the PENDING will busy-loop waiting for it to either get + * queued or lose PENDING. Grabbing PENDING and queueing should + * happen with IRQ disabled. + */ + lockdep_assert_irqs_disabled(); + + + /* if draining, only works from the same workqueue are allowed */ + if (unlikely(wq->flags & __WQ_DRAINING) && + WARN_ON_ONCE(!is_chained_work(wq))) + return; +retry: + /* pwq which will be used unless @work is executing elsewhere */ + if (wq->flags & WQ_UNBOUND) { + if (req_cpu == WORK_CPU_UNBOUND) + cpu = wq_select_unbound_cpu(raw_smp_processor_id()); + pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); + } else { + if (req_cpu == WORK_CPU_UNBOUND) + cpu = raw_smp_processor_id(); + pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); + } + + /* + * If @work was previously on a different pool, it might still be + * running there, in which case the work needs to be queued on that + * pool to guarantee non-reentrancy. + */ + last_pool = get_work_pool(work); + if (last_pool && last_pool != pwq->pool) { + struct worker *worker; + + spin_lock(&last_pool->lock); + + worker = find_worker_executing_work(last_pool, work); + + if (worker && worker->current_pwq->wq == wq) { + pwq = worker->current_pwq; + } else { + /* meh... not running there, queue here */ + spin_unlock(&last_pool->lock); + spin_lock(&pwq->pool->lock); + } + } else { + spin_lock(&pwq->pool->lock); + } + + /* + * pwq is determined and locked. For unbound pools, we could have + * raced with pwq release and it could already be dead. If its + * refcnt is zero, repeat pwq selection. Note that pwqs never die + * without another pwq replacing it in the numa_pwq_tbl or while + * work items are executing on it, so the retrying is guaranteed to + * make forward-progress. + */ + if (unlikely(!pwq->refcnt)) { + if (wq->flags & WQ_UNBOUND) { + spin_unlock(&pwq->pool->lock); + cpu_relax(); + goto retry; + } + /* oops */ + WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt", + wq->name, cpu); + } + + /* pwq determined, queue */ + trace_workqueue_queue_work(req_cpu, pwq, work); + + if (WARN_ON(!list_empty(&work->entry))) { + spin_unlock(&pwq->pool->lock); + return; + } + + pwq->nr_in_flight[pwq->work_color]++; + work_flags = work_color_to_flags(pwq->work_color); + + if (likely(pwq->nr_active < pwq->max_active)) { + trace_workqueue_activate_work(work); + pwq->nr_active++; + worklist = &pwq->pool->worklist; + if (list_empty(worklist)) + pwq->pool->watchdog_ts = jiffies; + } else { + work_flags |= WORK_STRUCT_DELAYED; + worklist = &pwq->delayed_works; + } + + debug_work_activate(work); + insert_work(pwq, work, worklist, work_flags); + + spin_unlock(&pwq->pool->lock); +} + +/** + * queue_work_on - queue work on specific cpu + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @work: work to queue + * + * We queue the work to a specific CPU, the caller must ensure it + * can't go away. + * + * Return: %false if @work was already on a queue, %true otherwise. + */ +bool queue_work_on(int cpu, struct workqueue_struct *wq, + struct work_struct *work) +{ + bool ret = false; + unsigned long flags; + + local_irq_save(flags); + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + __queue_work(cpu, wq, work); + ret = true; + } + + local_irq_restore(flags); + return ret; +} +EXPORT_SYMBOL(queue_work_on); + +void delayed_work_timer_fn(struct timer_list *t) +{ + struct delayed_work *dwork = from_timer(dwork, t, timer); + + /* should have been called from irqsafe timer with irq already off */ + __queue_work(dwork->cpu, dwork->wq, &dwork->work); +} +EXPORT_SYMBOL(delayed_work_timer_fn); + +static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, + struct delayed_work *dwork, unsigned long delay) +{ + struct timer_list *timer = &dwork->timer; + struct work_struct *work = &dwork->work; + + WARN_ON_ONCE(!wq); + WARN_ON_ONCE(timer->function != delayed_work_timer_fn); + WARN_ON_ONCE(timer_pending(timer)); + WARN_ON_ONCE(!list_empty(&work->entry)); + + /* + * If @delay is 0, queue @dwork->work immediately. This is for + * both optimization and correctness. The earliest @timer can + * expire is on the closest next tick and delayed_work users depend + * on that there's no such delay when @delay is 0. + */ + if (!delay) { + __queue_work(cpu, wq, &dwork->work); + return; + } + + dwork->wq = wq; + dwork->cpu = cpu; + timer->expires = jiffies + delay; + + if (unlikely(cpu != WORK_CPU_UNBOUND)) + add_timer_on(timer, cpu); + else + add_timer(timer); +} + +/** + * queue_delayed_work_on - queue work on specific CPU after delay + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @dwork: work to queue + * @delay: number of jiffies to wait before queueing + * + * Return: %false if @work was already on a queue, %true otherwise. If + * @delay is zero and @dwork is idle, it will be scheduled for immediate + * execution. + */ +bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, + struct delayed_work *dwork, unsigned long delay) +{ + struct work_struct *work = &dwork->work; + bool ret = false; + unsigned long flags; + + /* read the comment in __queue_work() */ + local_irq_save(flags); + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + __queue_delayed_work(cpu, wq, dwork, delay); + ret = true; + } + + local_irq_restore(flags); + return ret; +} +EXPORT_SYMBOL(queue_delayed_work_on); + +/** + * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @dwork: work to queue + * @delay: number of jiffies to wait before queueing + * + * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise, + * modify @dwork's timer so that it expires after @delay. If @delay is + * zero, @work is guaranteed to be scheduled immediately regardless of its + * current state. + * + * Return: %false if @dwork was idle and queued, %true if @dwork was + * pending and its timer was modified. + * + * This function is safe to call from any context including IRQ handler. + * See try_to_grab_pending() for details. + */ +bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, + struct delayed_work *dwork, unsigned long delay) +{ + unsigned long flags; + int ret; + + do { + ret = try_to_grab_pending(&dwork->work, true, &flags); + } while (unlikely(ret == -EAGAIN)); + + if (likely(ret >= 0)) { + __queue_delayed_work(cpu, wq, dwork, delay); + local_irq_restore(flags); + } + + /* -ENOENT from try_to_grab_pending() becomes %true */ + return ret; +} +EXPORT_SYMBOL_GPL(mod_delayed_work_on); + +static void rcu_work_rcufn(struct rcu_head *rcu) +{ + struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu); + + /* read the comment in __queue_work() */ + local_irq_disable(); + __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work); + local_irq_enable(); +} + +/** + * queue_rcu_work - queue work after a RCU grace period + * @wq: workqueue to use + * @rwork: work to queue + * + * Return: %false if @rwork was already pending, %true otherwise. Note + * that a full RCU grace period is guaranteed only after a %true return. + * While @rwork is guarnateed to be executed after a %false return, the + * execution may happen before a full RCU grace period has passed. + */ +bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork) +{ + struct work_struct *work = &rwork->work; + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + rwork->wq = wq; + call_rcu(&rwork->rcu, rcu_work_rcufn); + return true; + } + + return false; +} +EXPORT_SYMBOL(queue_rcu_work); + +/** + * worker_enter_idle - enter idle state + * @worker: worker which is entering idle state + * + * @worker is entering idle state. Update stats and idle timer if + * necessary. + * + * LOCKING: + * spin_lock_irq(pool->lock). + */ +static void worker_enter_idle(struct worker *worker) +{ + struct worker_pool *pool = worker->pool; + + if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) || + WARN_ON_ONCE(!list_empty(&worker->entry) && + (worker->hentry.next || worker->hentry.pprev))) + return; + + /* can't use worker_set_flags(), also called from create_worker() */ + worker->flags |= WORKER_IDLE; + pool->nr_idle++; + worker->last_active = jiffies; + + /* idle_list is LIFO */ + list_add(&worker->entry, &pool->idle_list); + + if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) + mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); + + /* + * Sanity check nr_running. Because unbind_workers() releases + * pool->lock between setting %WORKER_UNBOUND and zapping + * nr_running, the warning may trigger spuriously. Check iff + * unbind is not in progress. + */ + WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && + pool->nr_workers == pool->nr_idle && + atomic_read(&pool->nr_running)); +} + +/** + * worker_leave_idle - leave idle state + * @worker: worker which is leaving idle state + * + * @worker is leaving idle state. Update stats. + * + * LOCKING: + * spin_lock_irq(pool->lock). + */ +static void worker_leave_idle(struct worker *worker) +{ + struct worker_pool *pool = worker->pool; + + if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE))) + return; + worker_clr_flags(worker, WORKER_IDLE); + pool->nr_idle--; + list_del_init(&worker->entry); +} + +static struct worker *alloc_worker(int node) +{ + struct worker *worker; + + worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); + if (worker) { + INIT_LIST_HEAD(&worker->entry); + INIT_LIST_HEAD(&worker->scheduled); + INIT_LIST_HEAD(&worker->node); + /* on creation a worker is in !idle && prep state */ + worker->flags = WORKER_PREP; + } + return worker; +} + +/** + * worker_attach_to_pool() - attach a worker to a pool + * @worker: worker to be attached + * @pool: the target pool + * + * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and + * cpu-binding of @worker are kept coordinated with the pool across + * cpu-[un]hotplugs. + */ +static void worker_attach_to_pool(struct worker *worker, + struct worker_pool *pool) +{ + mutex_lock(&wq_pool_attach_mutex); + + /* + * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains + * stable across this function. See the comments above the flag + * definition for details. + */ + if (pool->flags & POOL_DISASSOCIATED) + worker->flags |= WORKER_UNBOUND; + + if (worker->rescue_wq) + set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); + + list_add_tail(&worker->node, &pool->workers); + worker->pool = pool; + + mutex_unlock(&wq_pool_attach_mutex); +} + +/** + * worker_detach_from_pool() - detach a worker from its pool + * @worker: worker which is attached to its pool + * + * Undo the attaching which had been done in worker_attach_to_pool(). The + * caller worker shouldn't access to the pool after detached except it has + * other reference to the pool. + */ +static void worker_detach_from_pool(struct worker *worker) +{ + struct worker_pool *pool = worker->pool; + struct completion *detach_completion = NULL; + + mutex_lock(&wq_pool_attach_mutex); + + list_del(&worker->node); + worker->pool = NULL; + + if (list_empty(&pool->workers)) + detach_completion = pool->detach_completion; + mutex_unlock(&wq_pool_attach_mutex); + + /* clear leftover flags without pool->lock after it is detached */ + worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND); + + if (detach_completion) + complete(detach_completion); +} + +/** + * create_worker - create a new workqueue worker + * @pool: pool the new worker will belong to + * + * Create and start a new worker which is attached to @pool. + * + * CONTEXT: + * Might sleep. Does GFP_KERNEL allocations. + * + * Return: + * Pointer to the newly created worker. + */ +static struct worker *create_worker(struct worker_pool *pool) +{ + struct worker *worker = NULL; + int id = -1; + char id_buf[16]; + + /* ID is needed to determine kthread name */ + id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL); + if (id < 0) + goto fail; + + worker = alloc_worker(pool->node); + if (!worker) + goto fail; + + worker->id = id; + + if (pool->cpu >= 0) + snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id, + pool->attrs->nice < 0 ? "H" : ""); + else + snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id); + + worker->task = kthread_create_on_node(worker_thread, worker, pool->node, + "kworker/%s", id_buf); + if (IS_ERR(worker->task)) + goto fail; + + set_user_nice(worker->task, pool->attrs->nice); + kthread_bind_mask(worker->task, pool->attrs->cpumask); + + /* successful, attach the worker to the pool */ + worker_attach_to_pool(worker, pool); + + /* start the newly created worker */ + spin_lock_irq(&pool->lock); + worker->pool->nr_workers++; + worker_enter_idle(worker); + wake_up_process(worker->task); + spin_unlock_irq(&pool->lock); + + return worker; + +fail: + if (id >= 0) + ida_simple_remove(&pool->worker_ida, id); + kfree(worker); + return NULL; +} + +/** + * destroy_worker - destroy a workqueue worker + * @worker: worker to be destroyed + * + * Destroy @worker and adjust @pool stats accordingly. The worker should + * be idle. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void destroy_worker(struct worker *worker) +{ + struct worker_pool *pool = worker->pool; + + lockdep_assert_held(&pool->lock); + + /* sanity check frenzy */ + if (WARN_ON(worker->current_work) || + WARN_ON(!list_empty(&worker->scheduled)) || + WARN_ON(!(worker->flags & WORKER_IDLE))) + return; + + pool->nr_workers--; + pool->nr_idle--; + + list_del_init(&worker->entry); + worker->flags |= WORKER_DIE; + wake_up_process(worker->task); +} + +static void idle_worker_timeout(struct timer_list *t) +{ + struct worker_pool *pool = from_timer(pool, t, idle_timer); + + spin_lock_irq(&pool->lock); + + while (too_many_workers(pool)) { + struct worker *worker; + unsigned long expires; + + /* idle_list is kept in LIFO order, check the last one */ + worker = list_entry(pool->idle_list.prev, struct worker, entry); + expires = worker->last_active + IDLE_WORKER_TIMEOUT; + + if (time_before(jiffies, expires)) { + mod_timer(&pool->idle_timer, expires); + break; + } + + destroy_worker(worker); + } + + spin_unlock_irq(&pool->lock); +} + +static void send_mayday(struct work_struct *work) +{ + struct pool_workqueue *pwq = get_work_pwq(work); + struct workqueue_struct *wq = pwq->wq; + + lockdep_assert_held(&wq_mayday_lock); + + if (!wq->rescuer) + return; + + /* mayday mayday mayday */ + if (list_empty(&pwq->mayday_node)) { + /* + * If @pwq is for an unbound wq, its base ref may be put at + * any time due to an attribute change. Pin @pwq until the + * rescuer is done with it. + */ + get_pwq(pwq); + list_add_tail(&pwq->mayday_node, &wq->maydays); + wake_up_process(wq->rescuer->task); + } +} + +static void pool_mayday_timeout(struct timer_list *t) +{ + struct worker_pool *pool = from_timer(pool, t, mayday_timer); + struct work_struct *work; + + spin_lock_irq(&pool->lock); + spin_lock(&wq_mayday_lock); /* for wq->maydays */ + + if (need_to_create_worker(pool)) { + /* + * We've been trying to create a new worker but + * haven't been successful. We might be hitting an + * allocation deadlock. Send distress signals to + * rescuers. + */ + list_for_each_entry(work, &pool->worklist, entry) + send_mayday(work); + } + + spin_unlock(&wq_mayday_lock); + spin_unlock_irq(&pool->lock); + + mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); +} + +/** + * maybe_create_worker - create a new worker if necessary + * @pool: pool to create a new worker for + * + * Create a new worker for @pool if necessary. @pool is guaranteed to + * have at least one idle worker on return from this function. If + * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is + * sent to all rescuers with works scheduled on @pool to resolve + * possible allocation deadlock. + * + * On return, need_to_create_worker() is guaranteed to be %false and + * may_start_working() %true. + * + * LOCKING: + * spin_lock_irq(pool->lock) which may be released and regrabbed + * multiple times. Does GFP_KERNEL allocations. Called only from + * manager. + */ +static void maybe_create_worker(struct worker_pool *pool) +__releases(&pool->lock) +__acquires(&pool->lock) +{ +restart: + spin_unlock_irq(&pool->lock); + + /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ + mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); + + while (true) { + if (create_worker(pool) || !need_to_create_worker(pool)) + break; + + schedule_timeout_interruptible(CREATE_COOLDOWN); + + if (!need_to_create_worker(pool)) + break; + } + + del_timer_sync(&pool->mayday_timer); + spin_lock_irq(&pool->lock); + /* + * This is necessary even after a new worker was just successfully + * created as @pool->lock was dropped and the new worker might have + * already become busy. + */ + if (need_to_create_worker(pool)) + goto restart; +} + +/** + * manage_workers - manage worker pool + * @worker: self + * + * Assume the manager role and manage the worker pool @worker belongs + * to. At any given time, there can be only zero or one manager per + * pool. The exclusion is handled automatically by this function. + * + * The caller can safely start processing works on false return. On + * true return, it's guaranteed that need_to_create_worker() is false + * and may_start_working() is true. + * + * CONTEXT: + * spin_lock_irq(pool->lock) which may be released and regrabbed + * multiple times. Does GFP_KERNEL allocations. + * + * Return: + * %false if the pool doesn't need management and the caller can safely + * start processing works, %true if management function was performed and + * the conditions that the caller verified before calling the function may + * no longer be true. + */ +static bool manage_workers(struct worker *worker) +{ + struct worker_pool *pool = worker->pool; + + if (pool->flags & POOL_MANAGER_ACTIVE) + return false; + + pool->flags |= POOL_MANAGER_ACTIVE; + pool->manager = worker; + + maybe_create_worker(pool); + + pool->manager = NULL; + pool->flags &= ~POOL_MANAGER_ACTIVE; + wake_up(&wq_manager_wait); + return true; +} + +/** + * process_one_work - process single work + * @worker: self + * @work: work to process + * + * Process @work. This function contains all the logics necessary to + * process a single work including synchronization against and + * interaction with other workers on the same cpu, queueing and + * flushing. As long as context requirement is met, any worker can + * call this function to process a work. + * + * CONTEXT: + * spin_lock_irq(pool->lock) which is released and regrabbed. + */ +static void process_one_work(struct worker *worker, struct work_struct *work) +__releases(&pool->lock) +__acquires(&pool->lock) +{ + struct pool_workqueue *pwq = get_work_pwq(work); + struct worker_pool *pool = worker->pool; + bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE; + int work_color; + struct worker *collision; +#ifdef CONFIG_LOCKDEP + /* + * It is permissible to free the struct work_struct from + * inside the function that is called from it, this we need to + * take into account for lockdep too. To avoid bogus "held + * lock freed" warnings as well as problems when looking into + * work->lockdep_map, make a copy and use that here. + */ + struct lockdep_map lockdep_map; + + lockdep_copy_map(&lockdep_map, &work->lockdep_map); +#endif + /* ensure we're on the correct CPU */ + WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && + raw_smp_processor_id() != pool->cpu); + + /* + * A single work shouldn't be executed concurrently by + * multiple workers on a single cpu. Check whether anyone is + * already processing the work. If so, defer the work to the + * currently executing one. + */ + collision = find_worker_executing_work(pool, work); + if (unlikely(collision)) { + move_linked_works(work, &collision->scheduled, NULL); + return; + } + + /* claim and dequeue */ + debug_work_deactivate(work); + hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work); + worker->current_work = work; + worker->current_func = work->func; + worker->current_pwq = pwq; + work_color = get_work_color(work); + + /* + * Record wq name for cmdline and debug reporting, may get + * overridden through set_worker_desc(). + */ + strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN); + + list_del_init(&work->entry); + + /* + * CPU intensive works don't participate in concurrency management. + * They're the scheduler's responsibility. This takes @worker out + * of concurrency management and the next code block will chain + * execution of the pending work items. + */ + if (unlikely(cpu_intensive)) + worker_set_flags(worker, WORKER_CPU_INTENSIVE); + + /* + * Wake up another worker if necessary. The condition is always + * false for normal per-cpu workers since nr_running would always + * be >= 1 at this point. This is used to chain execution of the + * pending work items for WORKER_NOT_RUNNING workers such as the + * UNBOUND and CPU_INTENSIVE ones. + */ + if (need_more_worker(pool)) + wake_up_worker(pool); + + /* + * Record the last pool and clear PENDING which should be the last + * update to @work. Also, do this inside @pool->lock so that + * PENDING and queued state changes happen together while IRQ is + * disabled. + */ + set_work_pool_and_clear_pending(work, pool->id); + + spin_unlock_irq(&pool->lock); + + lock_map_acquire(&pwq->wq->lockdep_map); + lock_map_acquire(&lockdep_map); + /* + * Strictly speaking we should mark the invariant state without holding + * any locks, that is, before these two lock_map_acquire()'s. + * + * However, that would result in: + * + * A(W1) + * WFC(C) + * A(W1) + * C(C) + * + * Which would create W1->C->W1 dependencies, even though there is no + * actual deadlock possible. There are two solutions, using a + * read-recursive acquire on the work(queue) 'locks', but this will then + * hit the lockdep limitation on recursive locks, or simply discard + * these locks. + * + * AFAICT there is no possible deadlock scenario between the + * flush_work() and complete() primitives (except for single-threaded + * workqueues), so hiding them isn't a problem. + */ + lockdep_invariant_state(true); + trace_workqueue_execute_start(work); + worker->current_func(work); + /* + * While we must be careful to not use "work" after this, the trace + * point will only record its address. + */ + trace_workqueue_execute_end(work); + lock_map_release(&lockdep_map); + lock_map_release(&pwq->wq->lockdep_map); + + if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { + pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" + " last function: %pf\n", + current->comm, preempt_count(), task_pid_nr(current), + worker->current_func); + debug_show_held_locks(current); + dump_stack(); + } + + /* + * The following prevents a kworker from hogging CPU on !PREEMPT + * kernels, where a requeueing work item waiting for something to + * happen could deadlock with stop_machine as such work item could + * indefinitely requeue itself while all other CPUs are trapped in + * stop_machine. At the same time, report a quiescent RCU state so + * the same condition doesn't freeze RCU. + */ + cond_resched(); + + spin_lock_irq(&pool->lock); + + /* clear cpu intensive status */ + if (unlikely(cpu_intensive)) + worker_clr_flags(worker, WORKER_CPU_INTENSIVE); + + /* we're done with it, release */ + hash_del(&worker->hentry); + worker->current_work = NULL; + worker->current_func = NULL; + worker->current_pwq = NULL; + pwq_dec_nr_in_flight(pwq, work_color); +} + +/** + * process_scheduled_works - process scheduled works + * @worker: self + * + * Process all scheduled works. Please note that the scheduled list + * may change while processing a work, so this function repeatedly + * fetches a work from the top and executes it. + * + * CONTEXT: + * spin_lock_irq(pool->lock) which may be released and regrabbed + * multiple times. + */ +static void process_scheduled_works(struct worker *worker) +{ + while (!list_empty(&worker->scheduled)) { + struct work_struct *work = list_first_entry(&worker->scheduled, + struct work_struct, entry); + process_one_work(worker, work); + } +} + +static void set_pf_worker(bool val) +{ + mutex_lock(&wq_pool_attach_mutex); + if (val) + current->flags |= PF_WQ_WORKER; + else + current->flags &= ~PF_WQ_WORKER; + mutex_unlock(&wq_pool_attach_mutex); +} + +/** + * worker_thread - the worker thread function + * @__worker: self + * + * The worker thread function. All workers belong to a worker_pool - + * either a per-cpu one or dynamic unbound one. These workers process all + * work items regardless of their specific target workqueue. The only + * exception is work items which belong to workqueues with a rescuer which + * will be explained in rescuer_thread(). + * + * Return: 0 + */ +static int worker_thread(void *__worker) +{ + struct worker *worker = __worker; + struct worker_pool *pool = worker->pool; + + /* tell the scheduler that this is a workqueue worker */ + set_pf_worker(true); +woke_up: + spin_lock_irq(&pool->lock); + + /* am I supposed to die? */ + if (unlikely(worker->flags & WORKER_DIE)) { + spin_unlock_irq(&pool->lock); + WARN_ON_ONCE(!list_empty(&worker->entry)); + set_pf_worker(false); + + set_task_comm(worker->task, "kworker/dying"); + ida_simple_remove(&pool->worker_ida, worker->id); + worker_detach_from_pool(worker); + kfree(worker); + return 0; + } + + worker_leave_idle(worker); +recheck: + /* no more worker necessary? */ + if (!need_more_worker(pool)) + goto sleep; + + /* do we need to manage? */ + if (unlikely(!may_start_working(pool)) && manage_workers(worker)) + goto recheck; + + /* + * ->scheduled list can only be filled while a worker is + * preparing to process a work or actually processing it. + * Make sure nobody diddled with it while I was sleeping. + */ + WARN_ON_ONCE(!list_empty(&worker->scheduled)); + + /* + * Finish PREP stage. We're guaranteed to have at least one idle + * worker or that someone else has already assumed the manager + * role. This is where @worker starts participating in concurrency + * management if applicable and concurrency management is restored + * after being rebound. See rebind_workers() for details. + */ + worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND); + + do { + struct work_struct *work = + list_first_entry(&pool->worklist, + struct work_struct, entry); + + pool->watchdog_ts = jiffies; + + if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { + /* optimization path, not strictly necessary */ + process_one_work(worker, work); + if (unlikely(!list_empty(&worker->scheduled))) + process_scheduled_works(worker); + } else { + move_linked_works(work, &worker->scheduled, NULL); + process_scheduled_works(worker); + } + } while (keep_working(pool)); + + worker_set_flags(worker, WORKER_PREP); +sleep: + /* + * pool->lock is held and there's no work to process and no need to + * manage, sleep. Workers are woken up only while holding + * pool->lock or from local cpu, so setting the current state + * before releasing pool->lock is enough to prevent losing any + * event. + */ + worker_enter_idle(worker); + __set_current_state(TASK_IDLE); + spin_unlock_irq(&pool->lock); + schedule(); + goto woke_up; +} + +/** + * rescuer_thread - the rescuer thread function + * @__rescuer: self + * + * Workqueue rescuer thread function. There's one rescuer for each + * workqueue which has WQ_MEM_RECLAIM set. + * + * Regular work processing on a pool may block trying to create a new + * worker which uses GFP_KERNEL allocation which has slight chance of + * developing into deadlock if some works currently on the same queue + * need to be processed to satisfy the GFP_KERNEL allocation. This is + * the problem rescuer solves. + * + * When such condition is possible, the pool summons rescuers of all + * workqueues which have works queued on the pool and let them process + * those works so that forward progress can be guaranteed. + * + * This should happen rarely. + * + * Return: 0 + */ +static int rescuer_thread(void *__rescuer) +{ + struct worker *rescuer = __rescuer; + struct workqueue_struct *wq = rescuer->rescue_wq; + struct list_head *scheduled = &rescuer->scheduled; + bool should_stop; + + set_user_nice(current, RESCUER_NICE_LEVEL); + + /* + * Mark rescuer as worker too. As WORKER_PREP is never cleared, it + * doesn't participate in concurrency management. + */ + set_pf_worker(true); +repeat: + set_current_state(TASK_IDLE); + + /* + * By the time the rescuer is requested to stop, the workqueue + * shouldn't have any work pending, but @wq->maydays may still have + * pwq(s) queued. This can happen by non-rescuer workers consuming + * all the work items before the rescuer got to them. Go through + * @wq->maydays processing before acting on should_stop so that the + * list is always empty on exit. + */ + should_stop = kthread_should_stop(); + + /* see whether any pwq is asking for help */ + spin_lock_irq(&wq_mayday_lock); + + while (!list_empty(&wq->maydays)) { + struct pool_workqueue *pwq = list_first_entry(&wq->maydays, + struct pool_workqueue, mayday_node); + struct worker_pool *pool = pwq->pool; + struct work_struct *work, *n; + bool first = true; + + __set_current_state(TASK_RUNNING); + list_del_init(&pwq->mayday_node); + + spin_unlock_irq(&wq_mayday_lock); + + worker_attach_to_pool(rescuer, pool); + + spin_lock_irq(&pool->lock); + + /* + * Slurp in all works issued via this workqueue and + * process'em. + */ + WARN_ON_ONCE(!list_empty(scheduled)); + list_for_each_entry_safe(work, n, &pool->worklist, entry) { + if (get_work_pwq(work) == pwq) { + if (first) + pool->watchdog_ts = jiffies; + move_linked_works(work, scheduled, &n); + } + first = false; + } + + if (!list_empty(scheduled)) { + process_scheduled_works(rescuer); + + /* + * The above execution of rescued work items could + * have created more to rescue through + * pwq_activate_first_delayed() or chained + * queueing. Let's put @pwq back on mayday list so + * that such back-to-back work items, which may be + * being used to relieve memory pressure, don't + * incur MAYDAY_INTERVAL delay inbetween. + */ + if (need_to_create_worker(pool)) { + spin_lock(&wq_mayday_lock); + /* + * Queue iff we aren't racing destruction + * and somebody else hasn't queued it already. + */ + if (wq->rescuer && list_empty(&pwq->mayday_node)) { + get_pwq(pwq); + list_add_tail(&pwq->mayday_node, &wq->maydays); + } + spin_unlock(&wq_mayday_lock); + } + } + + /* + * Put the reference grabbed by send_mayday(). @pool won't + * go away while we're still attached to it. + */ + put_pwq(pwq); + + /* + * Leave this pool. If need_more_worker() is %true, notify a + * regular worker; otherwise, we end up with 0 concurrency + * and stalling the execution. + */ + if (need_more_worker(pool)) + wake_up_worker(pool); + + spin_unlock_irq(&pool->lock); + + worker_detach_from_pool(rescuer); + + spin_lock_irq(&wq_mayday_lock); + } + + spin_unlock_irq(&wq_mayday_lock); + + if (should_stop) { + __set_current_state(TASK_RUNNING); + set_pf_worker(false); + return 0; + } + + /* rescuers should never participate in concurrency management */ + WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); + schedule(); + goto repeat; +} + +/** + * check_flush_dependency - check for flush dependency sanity + * @target_wq: workqueue being flushed + * @target_work: work item being flushed (NULL for workqueue flushes) + * + * %current is trying to flush the whole @target_wq or @target_work on it. + * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not + * reclaiming memory or running on a workqueue which doesn't have + * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to + * a deadlock. + */ +static void check_flush_dependency(struct workqueue_struct *target_wq, + struct work_struct *target_work) +{ + work_func_t target_func = target_work ? target_work->func : NULL; + struct worker *worker; + + if (target_wq->flags & WQ_MEM_RECLAIM) + return; + + worker = current_wq_worker(); + + WARN_ONCE(current->flags & PF_MEMALLOC, + "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf", + current->pid, current->comm, target_wq->name, target_func); + WARN_ONCE(worker && ((worker->current_pwq->wq->flags & + (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM), + "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf", + worker->current_pwq->wq->name, worker->current_func, + target_wq->name, target_func); +} + +struct wq_barrier { + struct work_struct work; + struct completion done; + struct task_struct *task; /* purely informational */ +}; + +static void wq_barrier_func(struct work_struct *work) +{ + struct wq_barrier *barr = container_of(work, struct wq_barrier, work); + complete(&barr->done); +} + +/** + * insert_wq_barrier - insert a barrier work + * @pwq: pwq to insert barrier into + * @barr: wq_barrier to insert + * @target: target work to attach @barr to + * @worker: worker currently executing @target, NULL if @target is not executing + * + * @barr is linked to @target such that @barr is completed only after + * @target finishes execution. Please note that the ordering + * guarantee is observed only with respect to @target and on the local + * cpu. + * + * Currently, a queued barrier can't be canceled. This is because + * try_to_grab_pending() can't determine whether the work to be + * grabbed is at the head of the queue and thus can't clear LINKED + * flag of the previous work while there must be a valid next work + * after a work with LINKED flag set. + * + * Note that when @worker is non-NULL, @target may be modified + * underneath us, so we can't reliably determine pwq from @target. + * + * CONTEXT: + * spin_lock_irq(pool->lock). + */ +static void insert_wq_barrier(struct pool_workqueue *pwq, + struct wq_barrier *barr, + struct work_struct *target, struct worker *worker) +{ + struct list_head *head; + unsigned int linked = 0; + + /* + * debugobject calls are safe here even with pool->lock locked + * as we know for sure that this will not trigger any of the + * checks and call back into the fixup functions where we + * might deadlock. + */ + INIT_WORK_ONSTACK(&barr->work, wq_barrier_func); + __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); + + init_completion_map(&barr->done, &target->lockdep_map); + + barr->task = current; + + /* + * If @target is currently being executed, schedule the + * barrier to the worker; otherwise, put it after @target. + */ + if (worker) + head = worker->scheduled.next; + else { + unsigned long *bits = work_data_bits(target); + + head = target->entry.next; + /* there can already be other linked works, inherit and set */ + linked = *bits & WORK_STRUCT_LINKED; + __set_bit(WORK_STRUCT_LINKED_BIT, bits); + } + + debug_work_activate(&barr->work); + insert_work(pwq, &barr->work, head, + work_color_to_flags(WORK_NO_COLOR) | linked); +} + +/** + * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing + * @wq: workqueue being flushed + * @flush_color: new flush color, < 0 for no-op + * @work_color: new work color, < 0 for no-op + * + * Prepare pwqs for workqueue flushing. + * + * If @flush_color is non-negative, flush_color on all pwqs should be + * -1. If no pwq has in-flight commands at the specified color, all + * pwq->flush_color's stay at -1 and %false is returned. If any pwq + * has in flight commands, its pwq->flush_color is set to + * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq + * wakeup logic is armed and %true is returned. + * + * The caller should have initialized @wq->first_flusher prior to + * calling this function with non-negative @flush_color. If + * @flush_color is negative, no flush color update is done and %false + * is returned. + * + * If @work_color is non-negative, all pwqs should have the same + * work_color which is previous to @work_color and all will be + * advanced to @work_color. + * + * CONTEXT: + * mutex_lock(wq->mutex). + * + * Return: + * %true if @flush_color >= 0 and there's something to flush. %false + * otherwise. + */ +static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq, + int flush_color, int work_color) +{ + bool wait = false; + struct pool_workqueue *pwq; + + if (flush_color >= 0) { + WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush)); + atomic_set(&wq->nr_pwqs_to_flush, 1); + } + + for_each_pwq(pwq, wq) { + struct worker_pool *pool = pwq->pool; + + spin_lock_irq(&pool->lock); + + if (flush_color >= 0) { + WARN_ON_ONCE(pwq->flush_color != -1); + + if (pwq->nr_in_flight[flush_color]) { + pwq->flush_color = flush_color; + atomic_inc(&wq->nr_pwqs_to_flush); + wait = true; + } + } + + if (work_color >= 0) { + WARN_ON_ONCE(work_color != work_next_color(pwq->work_color)); + pwq->work_color = work_color; + } + + spin_unlock_irq(&pool->lock); + } + + if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush)) + complete(&wq->first_flusher->done); + + return wait; +} + +/** + * flush_workqueue - ensure that any scheduled work has run to completion. + * @wq: workqueue to flush + * + * This function sleeps until all work items which were queued on entry + * have finished execution, but it is not livelocked by new incoming ones. + */ +void flush_workqueue(struct workqueue_struct *wq) +{ + struct wq_flusher this_flusher = { + .list = LIST_HEAD_INIT(this_flusher.list), + .flush_color = -1, + .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map), + }; + int next_color; + + if (WARN_ON(!wq_online)) + return; + + lock_map_acquire(&wq->lockdep_map); + lock_map_release(&wq->lockdep_map); + + mutex_lock(&wq->mutex); + + /* + * Start-to-wait phase + */ + next_color = work_next_color(wq->work_color); + + if (next_color != wq->flush_color) { + /* + * Color space is not full. The current work_color + * becomes our flush_color and work_color is advanced + * by one. + */ + WARN_ON_ONCE(!list_empty(&wq->flusher_overflow)); + this_flusher.flush_color = wq->work_color; + wq->work_color = next_color; + + if (!wq->first_flusher) { + /* no flush in progress, become the first flusher */ + WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); + + wq->first_flusher = &this_flusher; + + if (!flush_workqueue_prep_pwqs(wq, wq->flush_color, + wq->work_color)) { + /* nothing to flush, done */ + wq->flush_color = next_color; + wq->first_flusher = NULL; + goto out_unlock; + } + } else { + /* wait in queue */ + WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color); + list_add_tail(&this_flusher.list, &wq->flusher_queue); + flush_workqueue_prep_pwqs(wq, -1, wq->work_color); + } + } else { + /* + * Oops, color space is full, wait on overflow queue. + * The next flush completion will assign us + * flush_color and transfer to flusher_queue. + */ + list_add_tail(&this_flusher.list, &wq->flusher_overflow); + } + + check_flush_dependency(wq, NULL); + + mutex_unlock(&wq->mutex); + + wait_for_completion(&this_flusher.done); + + /* + * Wake-up-and-cascade phase + * + * First flushers are responsible for cascading flushes and + * handling overflow. Non-first flushers can simply return. + */ + if (wq->first_flusher != &this_flusher) + return; + + mutex_lock(&wq->mutex); + + /* we might have raced, check again with mutex held */ + if (wq->first_flusher != &this_flusher) + goto out_unlock; + + wq->first_flusher = NULL; + + WARN_ON_ONCE(!list_empty(&this_flusher.list)); + WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); + + while (true) { + struct wq_flusher *next, *tmp; + + /* complete all the flushers sharing the current flush color */ + list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { + if (next->flush_color != wq->flush_color) + break; + list_del_init(&next->list); + complete(&next->done); + } + + WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) && + wq->flush_color != work_next_color(wq->work_color)); + + /* this flush_color is finished, advance by one */ + wq->flush_color = work_next_color(wq->flush_color); + + /* one color has been freed, handle overflow queue */ + if (!list_empty(&wq->flusher_overflow)) { + /* + * Assign the same color to all overflowed + * flushers, advance work_color and append to + * flusher_queue. This is the start-to-wait + * phase for these overflowed flushers. + */ + list_for_each_entry(tmp, &wq->flusher_overflow, list) + tmp->flush_color = wq->work_color; + + wq->work_color = work_next_color(wq->work_color); + + list_splice_tail_init(&wq->flusher_overflow, + &wq->flusher_queue); + flush_workqueue_prep_pwqs(wq, -1, wq->work_color); + } + + if (list_empty(&wq->flusher_queue)) { + WARN_ON_ONCE(wq->flush_color != wq->work_color); + break; + } + + /* + * Need to flush more colors. Make the next flusher + * the new first flusher and arm pwqs. + */ + WARN_ON_ONCE(wq->flush_color == wq->work_color); + WARN_ON_ONCE(wq->flush_color != next->flush_color); + + list_del_init(&next->list); + wq->first_flusher = next; + + if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1)) + break; + + /* + * Meh... this color is already done, clear first + * flusher and repeat cascading. + */ + wq->first_flusher = NULL; + } + +out_unlock: + mutex_unlock(&wq->mutex); +} +EXPORT_SYMBOL(flush_workqueue); + +/** + * drain_workqueue - drain a workqueue + * @wq: workqueue to drain + * + * Wait until the workqueue becomes empty. While draining is in progress, + * only chain queueing is allowed. IOW, only currently pending or running + * work items on @wq can queue further work items on it. @wq is flushed + * repeatedly until it becomes empty. The number of flushing is determined + * by the depth of chaining and should be relatively short. Whine if it + * takes too long. + */ +void drain_workqueue(struct workqueue_struct *wq) +{ + unsigned int flush_cnt = 0; + struct pool_workqueue *pwq; + + /* + * __queue_work() needs to test whether there are drainers, is much + * hotter than drain_workqueue() and already looks at @wq->flags. + * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers. + */ + mutex_lock(&wq->mutex); + if (!wq->nr_drainers++) + wq->flags |= __WQ_DRAINING; + mutex_unlock(&wq->mutex); +reflush: + flush_workqueue(wq); + + mutex_lock(&wq->mutex); + + for_each_pwq(pwq, wq) { + bool drained; + + spin_lock_irq(&pwq->pool->lock); + drained = !pwq->nr_active && list_empty(&pwq->delayed_works); + spin_unlock_irq(&pwq->pool->lock); + + if (drained) + continue; + + if (++flush_cnt == 10 || + (flush_cnt % 100 == 0 && flush_cnt <= 1000)) + pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n", + wq->name, flush_cnt); + + mutex_unlock(&wq->mutex); + goto reflush; + } + + if (!--wq->nr_drainers) + wq->flags &= ~__WQ_DRAINING; + mutex_unlock(&wq->mutex); +} +EXPORT_SYMBOL_GPL(drain_workqueue); + +static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, + bool from_cancel) +{ + struct worker *worker = NULL; + struct worker_pool *pool; + struct pool_workqueue *pwq; + + might_sleep(); + + local_irq_disable(); + pool = get_work_pool(work); + if (!pool) { + local_irq_enable(); + return false; + } + + spin_lock(&pool->lock); + /* see the comment in try_to_grab_pending() with the same code */ + pwq = get_work_pwq(work); + if (pwq) { + if (unlikely(pwq->pool != pool)) + goto already_gone; + } else { + worker = find_worker_executing_work(pool, work); + if (!worker) + goto already_gone; + pwq = worker->current_pwq; + } + + check_flush_dependency(pwq->wq, work); + + insert_wq_barrier(pwq, barr, work, worker); + spin_unlock_irq(&pool->lock); + + /* + * Force a lock recursion deadlock when using flush_work() inside a + * single-threaded or rescuer equipped workqueue. + * + * For single threaded workqueues the deadlock happens when the work + * is after the work issuing the flush_work(). For rescuer equipped + * workqueues the deadlock happens when the rescuer stalls, blocking + * forward progress. + */ + if (!from_cancel && + (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) { + lock_map_acquire(&pwq->wq->lockdep_map); + lock_map_release(&pwq->wq->lockdep_map); + } + + return true; +already_gone: + spin_unlock_irq(&pool->lock); + return false; +} + +static bool __flush_work(struct work_struct *work, bool from_cancel) +{ + struct wq_barrier barr; + + if (WARN_ON(!wq_online)) + return false; + + if (WARN_ON(!work->func)) + return false; + + if (!from_cancel) { + lock_map_acquire(&work->lockdep_map); + lock_map_release(&work->lockdep_map); + } + + if (start_flush_work(work, &barr, from_cancel)) { + wait_for_completion(&barr.done); + destroy_work_on_stack(&barr.work); + return true; + } else { + return false; + } +} + +/** + * flush_work - wait for a work to finish executing the last queueing instance + * @work: the work to flush + * + * Wait until @work has finished execution. @work is guaranteed to be idle + * on return if it hasn't been requeued since flush started. + * + * Return: + * %true if flush_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_work(struct work_struct *work) +{ + return __flush_work(work, false); +} +EXPORT_SYMBOL_GPL(flush_work); + +struct cwt_wait { + wait_queue_entry_t wait; + struct work_struct *work; +}; + +static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) +{ + struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait); + + if (cwait->work != key) + return 0; + return autoremove_wake_function(wait, mode, sync, key); +} + +static bool __cancel_work_timer(struct work_struct *work, bool is_dwork) +{ + static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq); + unsigned long flags; + int ret; + + do { + ret = try_to_grab_pending(work, is_dwork, &flags); + /* + * If someone else is already canceling, wait for it to + * finish. flush_work() doesn't work for PREEMPT_NONE + * because we may get scheduled between @work's completion + * and the other canceling task resuming and clearing + * CANCELING - flush_work() will return false immediately + * as @work is no longer busy, try_to_grab_pending() will + * return -ENOENT as @work is still being canceled and the + * other canceling task won't be able to clear CANCELING as + * we're hogging the CPU. + * + * Let's wait for completion using a waitqueue. As this + * may lead to the thundering herd problem, use a custom + * wake function which matches @work along with exclusive + * wait and wakeup. + */ + if (unlikely(ret == -ENOENT)) { + struct cwt_wait cwait; + + init_wait(&cwait.wait); + cwait.wait.func = cwt_wakefn; + cwait.work = work; + + prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait, + TASK_UNINTERRUPTIBLE); + if (work_is_canceling(work)) + schedule(); + finish_wait(&cancel_waitq, &cwait.wait); + } + } while (unlikely(ret < 0)); + + /* tell other tasks trying to grab @work to back off */ + mark_work_canceling(work); + local_irq_restore(flags); + + /* + * This allows canceling during early boot. We know that @work + * isn't executing. + */ + if (wq_online) + __flush_work(work, true); + + clear_work_data(work); + + /* + * Paired with prepare_to_wait() above so that either + * waitqueue_active() is visible here or !work_is_canceling() is + * visible there. + */ + smp_mb(); + if (waitqueue_active(&cancel_waitq)) + __wake_up(&cancel_waitq, TASK_NORMAL, 1, work); + + return ret; +} + +/** + * cancel_work_sync - cancel a work and wait for it to finish + * @work: the work to cancel + * + * Cancel @work and wait for its execution to finish. This function + * can be used even if the work re-queues itself or migrates to + * another workqueue. On return from this function, @work is + * guaranteed to be not pending or executing on any CPU. + * + * cancel_work_sync(&delayed_work->work) must not be used for + * delayed_work's. Use cancel_delayed_work_sync() instead. + * + * The caller must ensure that the workqueue on which @work was last + * queued can't be destroyed before this function returns. + * + * Return: + * %true if @work was pending, %false otherwise. + */ +bool cancel_work_sync(struct work_struct *work) +{ + return __cancel_work_timer(work, false); +} +EXPORT_SYMBOL_GPL(cancel_work_sync); + +/** + * flush_delayed_work - wait for a dwork to finish executing the last queueing + * @dwork: the delayed work to flush + * + * Delayed timer is cancelled and the pending work is queued for + * immediate execution. Like flush_work(), this function only + * considers the last queueing instance of @dwork. + * + * Return: + * %true if flush_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_delayed_work(struct delayed_work *dwork) +{ + local_irq_disable(); + if (del_timer_sync(&dwork->timer)) + __queue_work(dwork->cpu, dwork->wq, &dwork->work); + local_irq_enable(); + return flush_work(&dwork->work); +} +EXPORT_SYMBOL(flush_delayed_work); + +/** + * flush_rcu_work - wait for a rwork to finish executing the last queueing + * @rwork: the rcu work to flush + * + * Return: + * %true if flush_rcu_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_rcu_work(struct rcu_work *rwork) +{ + if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) { + rcu_barrier(); + flush_work(&rwork->work); + return true; + } else { + return flush_work(&rwork->work); + } +} +EXPORT_SYMBOL(flush_rcu_work); + +static bool __cancel_work(struct work_struct *work, bool is_dwork) +{ + unsigned long flags; + int ret; + + do { + ret = try_to_grab_pending(work, is_dwork, &flags); + } while (unlikely(ret == -EAGAIN)); + + if (unlikely(ret < 0)) + return false; + + set_work_pool_and_clear_pending(work, get_work_pool_id(work)); + local_irq_restore(flags); + return ret; +} + +/** + * cancel_delayed_work - cancel a delayed work + * @dwork: delayed_work to cancel + * + * Kill off a pending delayed_work. + * + * Return: %true if @dwork was pending and canceled; %false if it wasn't + * pending. + * + * Note: + * The work callback function may still be running on return, unless + * it returns %true and the work doesn't re-arm itself. Explicitly flush or + * use cancel_delayed_work_sync() to wait on it. + * + * This function is safe to call from any context including IRQ handler. + */ +bool cancel_delayed_work(struct delayed_work *dwork) +{ + return __cancel_work(&dwork->work, true); +} +EXPORT_SYMBOL(cancel_delayed_work); + +/** + * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish + * @dwork: the delayed work cancel + * + * This is cancel_work_sync() for delayed works. + * + * Return: + * %true if @dwork was pending, %false otherwise. + */ +bool cancel_delayed_work_sync(struct delayed_work *dwork) +{ + return __cancel_work_timer(&dwork->work, true); +} +EXPORT_SYMBOL(cancel_delayed_work_sync); + +/** + * schedule_on_each_cpu - execute a function synchronously on each online CPU + * @func: the function to call + * + * schedule_on_each_cpu() executes @func on each online CPU using the + * system workqueue and blocks until all CPUs have completed. + * schedule_on_each_cpu() is very slow. + * + * Return: + * 0 on success, -errno on failure. + */ +int schedule_on_each_cpu(work_func_t func) +{ + int cpu; + struct work_struct __percpu *works; + + works = alloc_percpu(struct work_struct); + if (!works) + return -ENOMEM; + + get_online_cpus(); + + for_each_online_cpu(cpu) { + struct work_struct *work = per_cpu_ptr(works, cpu); + + INIT_WORK(work, func); + schedule_work_on(cpu, work); + } + + for_each_online_cpu(cpu) + flush_work(per_cpu_ptr(works, cpu)); + + put_online_cpus(); + free_percpu(works); + return 0; +} + +/** + * execute_in_process_context - reliably execute the routine with user context + * @fn: the function to execute + * @ew: guaranteed storage for the execute work structure (must + * be available when the work executes) + * + * Executes the function immediately if process context is available, + * otherwise schedules the function for delayed execution. + * + * Return: 0 - function was executed + * 1 - function was scheduled for execution + */ +int execute_in_process_context(work_func_t fn, struct execute_work *ew) +{ + if (!in_interrupt()) { + fn(&ew->work); + return 0; + } + + INIT_WORK(&ew->work, fn); + schedule_work(&ew->work); + + return 1; +} +EXPORT_SYMBOL_GPL(execute_in_process_context); + +/** + * free_workqueue_attrs - free a workqueue_attrs + * @attrs: workqueue_attrs to free + * + * Undo alloc_workqueue_attrs(). + */ +void free_workqueue_attrs(struct workqueue_attrs *attrs) +{ + if (attrs) { + free_cpumask_var(attrs->cpumask); + kfree(attrs); + } +} + +/** + * alloc_workqueue_attrs - allocate a workqueue_attrs + * @gfp_mask: allocation mask to use + * + * Allocate a new workqueue_attrs, initialize with default settings and + * return it. + * + * Return: The allocated new workqueue_attr on success. %NULL on failure. + */ +struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask) +{ + struct workqueue_attrs *attrs; + + attrs = kzalloc(sizeof(*attrs), gfp_mask); + if (!attrs) + goto fail; + if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask)) + goto fail; + + cpumask_copy(attrs->cpumask, cpu_possible_mask); + return attrs; +fail: + free_workqueue_attrs(attrs); + return NULL; +} + +static void copy_workqueue_attrs(struct workqueue_attrs *to, + const struct workqueue_attrs *from) +{ + to->nice = from->nice; + cpumask_copy(to->cpumask, from->cpumask); + /* + * Unlike hash and equality test, this function doesn't ignore + * ->no_numa as it is used for both pool and wq attrs. Instead, + * get_unbound_pool() explicitly clears ->no_numa after copying. + */ + to->no_numa = from->no_numa; +} + +/* hash value of the content of @attr */ +static u32 wqattrs_hash(const struct workqueue_attrs *attrs) +{ + u32 hash = 0; + + hash = jhash_1word(attrs->nice, hash); + hash = jhash(cpumask_bits(attrs->cpumask), + BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash); + return hash; +} + +/* content equality test */ +static bool wqattrs_equal(const struct workqueue_attrs *a, + const struct workqueue_attrs *b) +{ + if (a->nice != b->nice) + return false; + if (!cpumask_equal(a->cpumask, b->cpumask)) + return false; + return true; +} + +/** + * init_worker_pool - initialize a newly zalloc'd worker_pool + * @pool: worker_pool to initialize + * + * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs. + * + * Return: 0 on success, -errno on failure. Even on failure, all fields + * inside @pool proper are initialized and put_unbound_pool() can be called + * on @pool safely to release it. + */ +static int init_worker_pool(struct worker_pool *pool) +{ + spin_lock_init(&pool->lock); + pool->id = -1; + pool->cpu = -1; + pool->node = NUMA_NO_NODE; + pool->flags |= POOL_DISASSOCIATED; + pool->watchdog_ts = jiffies; + INIT_LIST_HEAD(&pool->worklist); + INIT_LIST_HEAD(&pool->idle_list); + hash_init(pool->busy_hash); + + timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE); + + timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0); + + INIT_LIST_HEAD(&pool->workers); + + ida_init(&pool->worker_ida); + INIT_HLIST_NODE(&pool->hash_node); + pool->refcnt = 1; + + /* shouldn't fail above this point */ + pool->attrs = alloc_workqueue_attrs(GFP_KERNEL); + if (!pool->attrs) + return -ENOMEM; + return 0; +} + +static void rcu_free_wq(struct rcu_head *rcu) +{ + struct workqueue_struct *wq = + container_of(rcu, struct workqueue_struct, rcu); + + if (!(wq->flags & WQ_UNBOUND)) + free_percpu(wq->cpu_pwqs); + else + free_workqueue_attrs(wq->unbound_attrs); + + kfree(wq->rescuer); + kfree(wq); +} + +static void rcu_free_pool(struct rcu_head *rcu) +{ + struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu); + + ida_destroy(&pool->worker_ida); + free_workqueue_attrs(pool->attrs); + kfree(pool); +} + +/** + * put_unbound_pool - put a worker_pool + * @pool: worker_pool to put + * + * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU + * safe manner. get_unbound_pool() calls this function on its failure path + * and this function should be able to release pools which went through, + * successfully or not, init_worker_pool(). + * + * Should be called with wq_pool_mutex held. + */ +static void put_unbound_pool(struct worker_pool *pool) +{ + DECLARE_COMPLETION_ONSTACK(detach_completion); + struct worker *worker; + + lockdep_assert_held(&wq_pool_mutex); + + if (--pool->refcnt) + return; + + /* sanity checks */ + if (WARN_ON(!(pool->cpu < 0)) || + WARN_ON(!list_empty(&pool->worklist))) + return; + + /* release id and unhash */ + if (pool->id >= 0) + idr_remove(&worker_pool_idr, pool->id); + hash_del(&pool->hash_node); + + /* + * Become the manager and destroy all workers. This prevents + * @pool's workers from blocking on attach_mutex. We're the last + * manager and @pool gets freed with the flag set. + */ + spin_lock_irq(&pool->lock); + wait_event_lock_irq(wq_manager_wait, + !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock); + pool->flags |= POOL_MANAGER_ACTIVE; + + while ((worker = first_idle_worker(pool))) + destroy_worker(worker); + WARN_ON(pool->nr_workers || pool->nr_idle); + spin_unlock_irq(&pool->lock); + + mutex_lock(&wq_pool_attach_mutex); + if (!list_empty(&pool->workers)) + pool->detach_completion = &detach_completion; + mutex_unlock(&wq_pool_attach_mutex); + + if (pool->detach_completion) + wait_for_completion(pool->detach_completion); + + /* shut down the timers */ + del_timer_sync(&pool->idle_timer); + del_timer_sync(&pool->mayday_timer); + + /* sched-RCU protected to allow dereferences from get_work_pool() */ + call_rcu_sched(&pool->rcu, rcu_free_pool); +} + +/** + * get_unbound_pool - get a worker_pool with the specified attributes + * @attrs: the attributes of the worker_pool to get + * + * Obtain a worker_pool which has the same attributes as @attrs, bump the + * reference count and return it. If there already is a matching + * worker_pool, it will be used; otherwise, this function attempts to + * create a new one. + * + * Should be called with wq_pool_mutex held. + * + * Return: On success, a worker_pool with the same attributes as @attrs. + * On failure, %NULL. + */ +static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) +{ + u32 hash = wqattrs_hash(attrs); + struct worker_pool *pool; + int node; + int target_node = NUMA_NO_NODE; + + lockdep_assert_held(&wq_pool_mutex); + + /* do we already have a matching pool? */ + hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) { + if (wqattrs_equal(pool->attrs, attrs)) { + pool->refcnt++; + return pool; + } + } + + /* if cpumask is contained inside a NUMA node, we belong to that node */ + if (wq_numa_enabled) { + for_each_node(node) { + if (cpumask_subset(attrs->cpumask, + wq_numa_possible_cpumask[node])) { + target_node = node; + break; + } + } + } + + /* nope, create a new one */ + pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node); + if (!pool || init_worker_pool(pool) < 0) + goto fail; + + lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */ + copy_workqueue_attrs(pool->attrs, attrs); + pool->node = target_node; + + /* + * no_numa isn't a worker_pool attribute, always clear it. See + * 'struct workqueue_attrs' comments for detail. + */ + pool->attrs->no_numa = false; + + if (worker_pool_assign_id(pool) < 0) + goto fail; + + /* create and start the initial worker */ + if (wq_online && !create_worker(pool)) + goto fail; + + /* install */ + hash_add(unbound_pool_hash, &pool->hash_node, hash); + + return pool; +fail: + if (pool) + put_unbound_pool(pool); + return NULL; +} + +static void rcu_free_pwq(struct rcu_head *rcu) +{ + kmem_cache_free(pwq_cache, + container_of(rcu, struct pool_workqueue, rcu)); +} + +/* + * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt + * and needs to be destroyed. + */ +static void pwq_unbound_release_workfn(struct work_struct *work) +{ + struct pool_workqueue *pwq = container_of(work, struct pool_workqueue, + unbound_release_work); + struct workqueue_struct *wq = pwq->wq; + struct worker_pool *pool = pwq->pool; + bool is_last = false; + + /* + * when @pwq is not linked, it doesn't hold any reference to the + * @wq, and @wq is invalid to access. + */ + if (!list_empty(&pwq->pwqs_node)) { + if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) + return; + + mutex_lock(&wq->mutex); + list_del_rcu(&pwq->pwqs_node); + is_last = list_empty(&wq->pwqs); + mutex_unlock(&wq->mutex); + } + + mutex_lock(&wq_pool_mutex); + put_unbound_pool(pool); + mutex_unlock(&wq_pool_mutex); + + call_rcu_sched(&pwq->rcu, rcu_free_pwq); + + /* + * If we're the last pwq going away, @wq is already dead and no one + * is gonna access it anymore. Schedule RCU free. + */ + if (is_last) + call_rcu_sched(&wq->rcu, rcu_free_wq); +} + +/** + * pwq_adjust_max_active - update a pwq's max_active to the current setting + * @pwq: target pool_workqueue + * + * If @pwq isn't freezing, set @pwq->max_active to the associated + * workqueue's saved_max_active and activate delayed work items + * accordingly. If @pwq is freezing, clear @pwq->max_active to zero. + */ +static void pwq_adjust_max_active(struct pool_workqueue *pwq) +{ + struct workqueue_struct *wq = pwq->wq; + bool freezable = wq->flags & WQ_FREEZABLE; + unsigned long flags; + + /* for @wq->saved_max_active */ + lockdep_assert_held(&wq->mutex); + + /* fast exit for non-freezable wqs */ + if (!freezable && pwq->max_active == wq->saved_max_active) + return; + + /* this function can be called during early boot w/ irq disabled */ + spin_lock_irqsave(&pwq->pool->lock, flags); + + /* + * During [un]freezing, the caller is responsible for ensuring that + * this function is called at least once after @workqueue_freezing + * is updated and visible. + */ + if (!freezable || !workqueue_freezing) { + bool kick = false; + + pwq->max_active = wq->saved_max_active; + + while (!list_empty(&pwq->delayed_works) && + pwq->nr_active < pwq->max_active) { + pwq_activate_first_delayed(pwq); + kick = true; + } + + /* + * Need to kick a worker after thawed or an unbound wq's + * max_active is bumped. In realtime scenarios, always kicking a + * worker will cause interference on the isolated cpu cores, so + * let's kick iff work items were activated. + */ + if (kick) + wake_up_worker(pwq->pool); + } else { + pwq->max_active = 0; + } + + spin_unlock_irqrestore(&pwq->pool->lock, flags); +} + +/* initialize newly alloced @pwq which is associated with @wq and @pool */ +static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq, + struct worker_pool *pool) +{ + BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK); + + memset(pwq, 0, sizeof(*pwq)); + + pwq->pool = pool; + pwq->wq = wq; + pwq->flush_color = -1; + pwq->refcnt = 1; + INIT_LIST_HEAD(&pwq->delayed_works); + INIT_LIST_HEAD(&pwq->pwqs_node); + INIT_LIST_HEAD(&pwq->mayday_node); + INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn); +} + +/* sync @pwq with the current state of its associated wq and link it */ +static void link_pwq(struct pool_workqueue *pwq) +{ + struct workqueue_struct *wq = pwq->wq; + + lockdep_assert_held(&wq->mutex); + + /* may be called multiple times, ignore if already linked */ + if (!list_empty(&pwq->pwqs_node)) + return; + + /* set the matching work_color */ + pwq->work_color = wq->work_color; + + /* sync max_active to the current setting */ + pwq_adjust_max_active(pwq); + + /* link in @pwq */ + list_add_rcu(&pwq->pwqs_node, &wq->pwqs); +} + +/* obtain a pool matching @attr and create a pwq associating the pool and @wq */ +static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) +{ + struct worker_pool *pool; + struct pool_workqueue *pwq; + + lockdep_assert_held(&wq_pool_mutex); + + pool = get_unbound_pool(attrs); + if (!pool) + return NULL; + + pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node); + if (!pwq) { + put_unbound_pool(pool); + return NULL; + } + + init_pwq(pwq, wq, pool); + return pwq; +} + +/** + * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node + * @attrs: the wq_attrs of the default pwq of the target workqueue + * @node: the target NUMA node + * @cpu_going_down: if >= 0, the CPU to consider as offline + * @cpumask: outarg, the resulting cpumask + * + * Calculate the cpumask a workqueue with @attrs should use on @node. If + * @cpu_going_down is >= 0, that cpu is considered offline during + * calculation. The result is stored in @cpumask. + * + * If NUMA affinity is not enabled, @attrs->cpumask is always used. If + * enabled and @node has online CPUs requested by @attrs, the returned + * cpumask is the intersection of the possible CPUs of @node and + * @attrs->cpumask. + * + * The caller is responsible for ensuring that the cpumask of @node stays + * stable. + * + * Return: %true if the resulting @cpumask is different from @attrs->cpumask, + * %false if equal. + */ +static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node, + int cpu_going_down, cpumask_t *cpumask) +{ + if (!wq_numa_enabled || attrs->no_numa) + goto use_dfl; + + /* does @node have any online CPUs @attrs wants? */ + cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask); + if (cpu_going_down >= 0) + cpumask_clear_cpu(cpu_going_down, cpumask); + + if (cpumask_empty(cpumask)) + goto use_dfl; + + /* yeap, return possible CPUs in @node that @attrs wants */ + cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]); + + if (cpumask_empty(cpumask)) { + pr_warn_once("WARNING: workqueue cpumask: online intersect > " + "possible intersect\n"); + return false; + } + + return !cpumask_equal(cpumask, attrs->cpumask); + +use_dfl: + cpumask_copy(cpumask, attrs->cpumask); + return false; +} + +/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */ +static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq, + int node, + struct pool_workqueue *pwq) +{ + struct pool_workqueue *old_pwq; + + lockdep_assert_held(&wq_pool_mutex); + lockdep_assert_held(&wq->mutex); + + /* link_pwq() can handle duplicate calls */ + link_pwq(pwq); + + old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]); + rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq); + return old_pwq; +} + +/* context to store the prepared attrs & pwqs before applying */ +struct apply_wqattrs_ctx { + struct workqueue_struct *wq; /* target workqueue */ + struct workqueue_attrs *attrs; /* attrs to apply */ + struct list_head list; /* queued for batching commit */ + struct pool_workqueue *dfl_pwq; + struct pool_workqueue *pwq_tbl[]; +}; + +/* free the resources after success or abort */ +static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx) +{ + if (ctx) { + int node; + + for_each_node(node) + put_pwq_unlocked(ctx->pwq_tbl[node]); + put_pwq_unlocked(ctx->dfl_pwq); + + free_workqueue_attrs(ctx->attrs); + + kfree(ctx); + } +} + +/* allocate the attrs and pwqs for later installation */ +static struct apply_wqattrs_ctx * +apply_wqattrs_prepare(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) +{ + struct apply_wqattrs_ctx *ctx; + struct workqueue_attrs *new_attrs, *tmp_attrs; + int node; + + lockdep_assert_held(&wq_pool_mutex); + + ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL); + + new_attrs = alloc_workqueue_attrs(GFP_KERNEL); + tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL); + if (!ctx || !new_attrs || !tmp_attrs) + goto out_free; + + /* + * Calculate the attrs of the default pwq. + * If the user configured cpumask doesn't overlap with the + * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask. + */ + copy_workqueue_attrs(new_attrs, attrs); + cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask); + if (unlikely(cpumask_empty(new_attrs->cpumask))) + cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask); + + /* + * We may create multiple pwqs with differing cpumasks. Make a + * copy of @new_attrs which will be modified and used to obtain + * pools. + */ + copy_workqueue_attrs(tmp_attrs, new_attrs); + + /* + * If something goes wrong during CPU up/down, we'll fall back to + * the default pwq covering whole @attrs->cpumask. Always create + * it even if we don't use it immediately. + */ + ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs); + if (!ctx->dfl_pwq) + goto out_free; + + for_each_node(node) { + if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) { + ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs); + if (!ctx->pwq_tbl[node]) + goto out_free; + } else { + ctx->dfl_pwq->refcnt++; + ctx->pwq_tbl[node] = ctx->dfl_pwq; + } + } + + /* save the user configured attrs and sanitize it. */ + copy_workqueue_attrs(new_attrs, attrs); + cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask); + ctx->attrs = new_attrs; + + ctx->wq = wq; + free_workqueue_attrs(tmp_attrs); + return ctx; + +out_free: + free_workqueue_attrs(tmp_attrs); + free_workqueue_attrs(new_attrs); + apply_wqattrs_cleanup(ctx); + return NULL; +} + +/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */ +static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx) +{ + int node; + + /* all pwqs have been created successfully, let's install'em */ + mutex_lock(&ctx->wq->mutex); + + copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs); + + /* save the previous pwq and install the new one */ + for_each_node(node) + ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node, + ctx->pwq_tbl[node]); + + /* @dfl_pwq might not have been used, ensure it's linked */ + link_pwq(ctx->dfl_pwq); + swap(ctx->wq->dfl_pwq, ctx->dfl_pwq); + + mutex_unlock(&ctx->wq->mutex); +} + +static void apply_wqattrs_lock(void) +{ + /* CPUs should stay stable across pwq creations and installations */ + get_online_cpus(); + mutex_lock(&wq_pool_mutex); +} + +static void apply_wqattrs_unlock(void) +{ + mutex_unlock(&wq_pool_mutex); + put_online_cpus(); +} + +static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) +{ + struct apply_wqattrs_ctx *ctx; + + /* only unbound workqueues can change attributes */ + if (WARN_ON(!(wq->flags & WQ_UNBOUND))) + return -EINVAL; + + /* creating multiple pwqs breaks ordering guarantee */ + if (!list_empty(&wq->pwqs)) { + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT)) + return -EINVAL; + + wq->flags &= ~__WQ_ORDERED; + } + + ctx = apply_wqattrs_prepare(wq, attrs); + if (!ctx) + return -ENOMEM; + + /* the ctx has been prepared successfully, let's commit it */ + apply_wqattrs_commit(ctx); + apply_wqattrs_cleanup(ctx); + + return 0; +} + +/** + * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue + * @wq: the target workqueue + * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs() + * + * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA + * machines, this function maps a separate pwq to each NUMA node with + * possibles CPUs in @attrs->cpumask so that work items are affine to the + * NUMA node it was issued on. Older pwqs are released as in-flight work + * items finish. Note that a work item which repeatedly requeues itself + * back-to-back will stay on its current pwq. + * + * Performs GFP_KERNEL allocations. + * + * Return: 0 on success and -errno on failure. + */ +int apply_workqueue_attrs(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) +{ + int ret; + + apply_wqattrs_lock(); + ret = apply_workqueue_attrs_locked(wq, attrs); + apply_wqattrs_unlock(); + + return ret; +} +EXPORT_SYMBOL_GPL(apply_workqueue_attrs); + +/** + * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug + * @wq: the target workqueue + * @cpu: the CPU coming up or going down + * @online: whether @cpu is coming up or going down + * + * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and + * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of + * @wq accordingly. + * + * If NUMA affinity can't be adjusted due to memory allocation failure, it + * falls back to @wq->dfl_pwq which may not be optimal but is always + * correct. + * + * Note that when the last allowed CPU of a NUMA node goes offline for a + * workqueue with a cpumask spanning multiple nodes, the workers which were + * already executing the work items for the workqueue will lose their CPU + * affinity and may execute on any CPU. This is similar to how per-cpu + * workqueues behave on CPU_DOWN. If a workqueue user wants strict + * affinity, it's the user's responsibility to flush the work item from + * CPU_DOWN_PREPARE. + */ +static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu, + bool online) +{ + int node = cpu_to_node(cpu); + int cpu_off = online ? -1 : cpu; + struct pool_workqueue *old_pwq = NULL, *pwq; + struct workqueue_attrs *target_attrs; + cpumask_t *cpumask; + + lockdep_assert_held(&wq_pool_mutex); + + if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) || + wq->unbound_attrs->no_numa) + return; + + /* + * We don't wanna alloc/free wq_attrs for each wq for each CPU. + * Let's use a preallocated one. The following buf is protected by + * CPU hotplug exclusion. + */ + target_attrs = wq_update_unbound_numa_attrs_buf; + cpumask = target_attrs->cpumask; + + copy_workqueue_attrs(target_attrs, wq->unbound_attrs); + pwq = unbound_pwq_by_node(wq, node); + + /* + * Let's determine what needs to be done. If the target cpumask is + * different from the default pwq's, we need to compare it to @pwq's + * and create a new one if they don't match. If the target cpumask + * equals the default pwq's, the default pwq should be used. + */ + if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) { + if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask)) + return; + } else { + goto use_dfl_pwq; + } + + /* create a new pwq */ + pwq = alloc_unbound_pwq(wq, target_attrs); + if (!pwq) { + pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n", + wq->name); + goto use_dfl_pwq; + } + + /* Install the new pwq. */ + mutex_lock(&wq->mutex); + old_pwq = numa_pwq_tbl_install(wq, node, pwq); + goto out_unlock; + +use_dfl_pwq: + mutex_lock(&wq->mutex); + spin_lock_irq(&wq->dfl_pwq->pool->lock); + get_pwq(wq->dfl_pwq); + spin_unlock_irq(&wq->dfl_pwq->pool->lock); + old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq); +out_unlock: + mutex_unlock(&wq->mutex); + put_pwq_unlocked(old_pwq); +} + +static int alloc_and_link_pwqs(struct workqueue_struct *wq) +{ + bool highpri = wq->flags & WQ_HIGHPRI; + int cpu, ret; + + if (!(wq->flags & WQ_UNBOUND)) { + wq->cpu_pwqs = alloc_percpu(struct pool_workqueue); + if (!wq->cpu_pwqs) + return -ENOMEM; + + for_each_possible_cpu(cpu) { + struct pool_workqueue *pwq = + per_cpu_ptr(wq->cpu_pwqs, cpu); + struct worker_pool *cpu_pools = + per_cpu(cpu_worker_pools, cpu); + + init_pwq(pwq, wq, &cpu_pools[highpri]); + + mutex_lock(&wq->mutex); + link_pwq(pwq); + mutex_unlock(&wq->mutex); + } + return 0; + } else if (wq->flags & __WQ_ORDERED) { + ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]); + /* there should only be single pwq for ordering guarantee */ + WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node || + wq->pwqs.prev != &wq->dfl_pwq->pwqs_node), + "ordering guarantee broken for workqueue %s\n", wq->name); + return ret; + } else { + return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]); + } +} + +static int wq_clamp_max_active(int max_active, unsigned int flags, + const char *name) +{ + int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE; + + if (max_active < 1 || max_active > lim) + pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n", + max_active, name, 1, lim); + + return clamp_val(max_active, 1, lim); +} + +/* + * Workqueues which may be used during memory reclaim should have a rescuer + * to guarantee forward progress. + */ +static int init_rescuer(struct workqueue_struct *wq) +{ + struct worker *rescuer; + int ret; + + if (!(wq->flags & WQ_MEM_RECLAIM)) + return 0; + + rescuer = alloc_worker(NUMA_NO_NODE); + if (!rescuer) + return -ENOMEM; + + rescuer->rescue_wq = wq; + rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name); + ret = PTR_ERR_OR_ZERO(rescuer->task); + if (ret) { + kfree(rescuer); + return ret; + } + + wq->rescuer = rescuer; + kthread_bind_mask(rescuer->task, cpu_possible_mask); + wake_up_process(rescuer->task); + + return 0; +} + +struct workqueue_struct *__alloc_workqueue_key(const char *fmt, + unsigned int flags, + int max_active, + struct lock_class_key *key, + const char *lock_name, ...) +{ + size_t tbl_size = 0; + va_list args; + struct workqueue_struct *wq; + struct pool_workqueue *pwq; + + /* + * Unbound && max_active == 1 used to imply ordered, which is no + * longer the case on NUMA machines due to per-node pools. While + * alloc_ordered_workqueue() is the right way to create an ordered + * workqueue, keep the previous behavior to avoid subtle breakages + * on NUMA. + */ + if ((flags & WQ_UNBOUND) && max_active == 1) + flags |= __WQ_ORDERED; + + /* see the comment above the definition of WQ_POWER_EFFICIENT */ + if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient) + flags |= WQ_UNBOUND; + + /* allocate wq and format name */ + if (flags & WQ_UNBOUND) + tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]); + + wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL); + if (!wq) + return NULL; + + if (flags & WQ_UNBOUND) { + wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL); + if (!wq->unbound_attrs) + goto err_free_wq; + } + + va_start(args, lock_name); + vsnprintf(wq->name, sizeof(wq->name), fmt, args); + va_end(args); + + max_active = max_active ?: WQ_DFL_ACTIVE; + max_active = wq_clamp_max_active(max_active, flags, wq->name); + + /* init wq */ + wq->flags = flags; + wq->saved_max_active = max_active; + mutex_init(&wq->mutex); + atomic_set(&wq->nr_pwqs_to_flush, 0); + INIT_LIST_HEAD(&wq->pwqs); + INIT_LIST_HEAD(&wq->flusher_queue); + INIT_LIST_HEAD(&wq->flusher_overflow); + INIT_LIST_HEAD(&wq->maydays); + + lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); + INIT_LIST_HEAD(&wq->list); + + if (alloc_and_link_pwqs(wq) < 0) + goto err_free_wq; + + if (wq_online && init_rescuer(wq) < 0) + goto err_destroy; + + if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq)) + goto err_destroy; + + /* + * wq_pool_mutex protects global freeze state and workqueues list. + * Grab it, adjust max_active and add the new @wq to workqueues + * list. + */ + mutex_lock(&wq_pool_mutex); + + mutex_lock(&wq->mutex); + for_each_pwq(pwq, wq) + pwq_adjust_max_active(pwq); + mutex_unlock(&wq->mutex); + + list_add_tail_rcu(&wq->list, &workqueues); + + mutex_unlock(&wq_pool_mutex); + + return wq; + +err_free_wq: + free_workqueue_attrs(wq->unbound_attrs); + kfree(wq); + return NULL; +err_destroy: + destroy_workqueue(wq); + return NULL; +} +EXPORT_SYMBOL_GPL(__alloc_workqueue_key); + +/** + * destroy_workqueue - safely terminate a workqueue + * @wq: target workqueue + * + * Safely destroy a workqueue. All work currently pending will be done first. + */ +void destroy_workqueue(struct workqueue_struct *wq) +{ + struct pool_workqueue *pwq; + int node; + + /* + * Remove it from sysfs first so that sanity check failure doesn't + * lead to sysfs name conflicts. + */ + workqueue_sysfs_unregister(wq); + + /* drain it before proceeding with destruction */ + drain_workqueue(wq); + + /* kill rescuer, if sanity checks fail, leave it w/o rescuer */ + if (wq->rescuer) { + struct worker *rescuer = wq->rescuer; + + /* this prevents new queueing */ + spin_lock_irq(&wq_mayday_lock); + wq->rescuer = NULL; + spin_unlock_irq(&wq_mayday_lock); + + /* rescuer will empty maydays list before exiting */ + kthread_stop(rescuer->task); + kfree(rescuer); + } + + /* sanity checks */ + mutex_lock(&wq->mutex); + for_each_pwq(pwq, wq) { + int i; + + for (i = 0; i < WORK_NR_COLORS; i++) { + if (WARN_ON(pwq->nr_in_flight[i])) { + mutex_unlock(&wq->mutex); + show_workqueue_state(); + return; + } + } + + if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) || + WARN_ON(pwq->nr_active) || + WARN_ON(!list_empty(&pwq->delayed_works))) { + mutex_unlock(&wq->mutex); + show_workqueue_state(); + return; + } + } + mutex_unlock(&wq->mutex); + + /* + * wq list is used to freeze wq, remove from list after + * flushing is complete in case freeze races us. + */ + mutex_lock(&wq_pool_mutex); + list_del_rcu(&wq->list); + mutex_unlock(&wq_pool_mutex); + + if (!(wq->flags & WQ_UNBOUND)) { + /* + * The base ref is never dropped on per-cpu pwqs. Directly + * schedule RCU free. + */ + call_rcu_sched(&wq->rcu, rcu_free_wq); + } else { + /* + * We're the sole accessor of @wq at this point. Directly + * access numa_pwq_tbl[] and dfl_pwq to put the base refs. + * @wq will be freed when the last pwq is released. + */ + for_each_node(node) { + pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]); + RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL); + put_pwq_unlocked(pwq); + } + + /* + * Put dfl_pwq. @wq may be freed any time after dfl_pwq is + * put. Don't access it afterwards. + */ + pwq = wq->dfl_pwq; + wq->dfl_pwq = NULL; + put_pwq_unlocked(pwq); + } +} +EXPORT_SYMBOL_GPL(destroy_workqueue); + +/** + * workqueue_set_max_active - adjust max_active of a workqueue + * @wq: target workqueue + * @max_active: new max_active value. + * + * Set max_active of @wq to @max_active. + * + * CONTEXT: + * Don't call from IRQ context. + */ +void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) +{ + struct pool_workqueue *pwq; + + /* disallow meddling with max_active for ordered workqueues */ + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT)) + return; + + max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); + + mutex_lock(&wq->mutex); + + wq->flags &= ~__WQ_ORDERED; + wq->saved_max_active = max_active; + + for_each_pwq(pwq, wq) + pwq_adjust_max_active(pwq); + + mutex_unlock(&wq->mutex); +} +EXPORT_SYMBOL_GPL(workqueue_set_max_active); + +/** + * current_work - retrieve %current task's work struct + * + * Determine if %current task is a workqueue worker and what it's working on. + * Useful to find out the context that the %current task is running in. + * + * Return: work struct if %current task is a workqueue worker, %NULL otherwise. + */ +struct work_struct *current_work(void) +{ + struct worker *worker = current_wq_worker(); + + return worker ? worker->current_work : NULL; +} +EXPORT_SYMBOL(current_work); + +/** + * current_is_workqueue_rescuer - is %current workqueue rescuer? + * + * Determine whether %current is a workqueue rescuer. Can be used from + * work functions to determine whether it's being run off the rescuer task. + * + * Return: %true if %current is a workqueue rescuer. %false otherwise. + */ +bool current_is_workqueue_rescuer(void) +{ + struct worker *worker = current_wq_worker(); + + return worker && worker->rescue_wq; +} + +/** + * workqueue_congested - test whether a workqueue is congested + * @cpu: CPU in question + * @wq: target workqueue + * + * Test whether @wq's cpu workqueue for @cpu is congested. There is + * no synchronization around this function and the test result is + * unreliable and only useful as advisory hints or for debugging. + * + * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU. + * Note that both per-cpu and unbound workqueues may be associated with + * multiple pool_workqueues which have separate congested states. A + * workqueue being congested on one CPU doesn't mean the workqueue is also + * contested on other CPUs / NUMA nodes. + * + * Return: + * %true if congested, %false otherwise. + */ +bool workqueue_congested(int cpu, struct workqueue_struct *wq) +{ + struct pool_workqueue *pwq; + bool ret; + + rcu_read_lock_sched(); + + if (cpu == WORK_CPU_UNBOUND) + cpu = smp_processor_id(); + + if (!(wq->flags & WQ_UNBOUND)) + pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); + else + pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); + + ret = !list_empty(&pwq->delayed_works); + rcu_read_unlock_sched(); + + return ret; +} +EXPORT_SYMBOL_GPL(workqueue_congested); + +/** + * work_busy - test whether a work is currently pending or running + * @work: the work to be tested + * + * Test whether @work is currently pending or running. There is no + * synchronization around this function and the test result is + * unreliable and only useful as advisory hints or for debugging. + * + * Return: + * OR'd bitmask of WORK_BUSY_* bits. + */ +unsigned int work_busy(struct work_struct *work) +{ + struct worker_pool *pool; + unsigned long flags; + unsigned int ret = 0; + + if (work_pending(work)) + ret |= WORK_BUSY_PENDING; + + local_irq_save(flags); + pool = get_work_pool(work); + if (pool) { + spin_lock(&pool->lock); + if (find_worker_executing_work(pool, work)) + ret |= WORK_BUSY_RUNNING; + spin_unlock(&pool->lock); + } + local_irq_restore(flags); + + return ret; +} +EXPORT_SYMBOL_GPL(work_busy); + +/** + * set_worker_desc - set description for the current work item + * @fmt: printf-style format string + * @...: arguments for the format string + * + * This function can be called by a running work function to describe what + * the work item is about. If the worker task gets dumped, this + * information will be printed out together to help debugging. The + * description can be at most WORKER_DESC_LEN including the trailing '\0'. + */ +void set_worker_desc(const char *fmt, ...) +{ + struct worker *worker = current_wq_worker(); + va_list args; + + if (worker) { + va_start(args, fmt); + vsnprintf(worker->desc, sizeof(worker->desc), fmt, args); + va_end(args); + } +} +EXPORT_SYMBOL_GPL(set_worker_desc); + +/** + * print_worker_info - print out worker information and description + * @log_lvl: the log level to use when printing + * @task: target task + * + * If @task is a worker and currently executing a work item, print out the + * name of the workqueue being serviced and worker description set with + * set_worker_desc() by the currently executing work item. + * + * This function can be safely called on any task as long as the + * task_struct itself is accessible. While safe, this function isn't + * synchronized and may print out mixups or garbages of limited length. + */ +void print_worker_info(const char *log_lvl, struct task_struct *task) +{ + work_func_t *fn = NULL; + char name[WQ_NAME_LEN] = { }; + char desc[WORKER_DESC_LEN] = { }; + struct pool_workqueue *pwq = NULL; + struct workqueue_struct *wq = NULL; + struct worker *worker; + + if (!(task->flags & PF_WQ_WORKER)) + return; + + /* + * This function is called without any synchronization and @task + * could be in any state. Be careful with dereferences. + */ + worker = kthread_probe_data(task); + + /* + * Carefully copy the associated workqueue's workfn, name and desc. + * Keep the original last '\0' in case the original is garbage. + */ + probe_kernel_read(&fn, &worker->current_func, sizeof(fn)); + probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq)); + probe_kernel_read(&wq, &pwq->wq, sizeof(wq)); + probe_kernel_read(name, wq->name, sizeof(name) - 1); + probe_kernel_read(desc, worker->desc, sizeof(desc) - 1); + + if (fn || name[0] || desc[0]) { + printk("%sWorkqueue: %s %pf", log_lvl, name, fn); + if (strcmp(name, desc)) + pr_cont(" (%s)", desc); + pr_cont("\n"); + } +} + +static void pr_cont_pool_info(struct worker_pool *pool) +{ + pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask); + if (pool->node != NUMA_NO_NODE) + pr_cont(" node=%d", pool->node); + pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice); +} + +static void pr_cont_work(bool comma, struct work_struct *work) +{ + if (work->func == wq_barrier_func) { + struct wq_barrier *barr; + + barr = container_of(work, struct wq_barrier, work); + + pr_cont("%s BAR(%d)", comma ? "," : "", + task_pid_nr(barr->task)); + } else { + pr_cont("%s %pf", comma ? "," : "", work->func); + } +} + +static void show_pwq(struct pool_workqueue *pwq) +{ + struct worker_pool *pool = pwq->pool; + struct work_struct *work; + struct worker *worker; + bool has_in_flight = false, has_pending = false; + int bkt; + + pr_info(" pwq %d:", pool->id); + pr_cont_pool_info(pool); + + pr_cont(" active=%d/%d refcnt=%d%s\n", + pwq->nr_active, pwq->max_active, pwq->refcnt, + !list_empty(&pwq->mayday_node) ? " MAYDAY" : ""); + + hash_for_each(pool->busy_hash, bkt, worker, hentry) { + if (worker->current_pwq == pwq) { + has_in_flight = true; + break; + } + } + if (has_in_flight) { + bool comma = false; + + pr_info(" in-flight:"); + hash_for_each(pool->busy_hash, bkt, worker, hentry) { + if (worker->current_pwq != pwq) + continue; + + pr_cont("%s %d%s:%pf", comma ? "," : "", + task_pid_nr(worker->task), + worker == pwq->wq->rescuer ? "(RESCUER)" : "", + worker->current_func); + list_for_each_entry(work, &worker->scheduled, entry) + pr_cont_work(false, work); + comma = true; + } + pr_cont("\n"); + } + + list_for_each_entry(work, &pool->worklist, entry) { + if (get_work_pwq(work) == pwq) { + has_pending = true; + break; + } + } + if (has_pending) { + bool comma = false; + + pr_info(" pending:"); + list_for_each_entry(work, &pool->worklist, entry) { + if (get_work_pwq(work) != pwq) + continue; + + pr_cont_work(comma, work); + comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED); + } + pr_cont("\n"); + } + + if (!list_empty(&pwq->delayed_works)) { + bool comma = false; + + pr_info(" delayed:"); + list_for_each_entry(work, &pwq->delayed_works, entry) { + pr_cont_work(comma, work); + comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED); + } + pr_cont("\n"); + } +} + +/** + * show_workqueue_state - dump workqueue state + * + * Called from a sysrq handler or try_to_freeze_tasks() and prints out + * all busy workqueues and pools. + */ +void show_workqueue_state(void) +{ + struct workqueue_struct *wq; + struct worker_pool *pool; + unsigned long flags; + int pi; + + rcu_read_lock_sched(); + + pr_info("Showing busy workqueues and worker pools:\n"); + + list_for_each_entry_rcu(wq, &workqueues, list) { + struct pool_workqueue *pwq; + bool idle = true; + + for_each_pwq(pwq, wq) { + if (pwq->nr_active || !list_empty(&pwq->delayed_works)) { + idle = false; + break; + } + } + if (idle) + continue; + + pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags); + + for_each_pwq(pwq, wq) { + spin_lock_irqsave(&pwq->pool->lock, flags); + if (pwq->nr_active || !list_empty(&pwq->delayed_works)) + show_pwq(pwq); + spin_unlock_irqrestore(&pwq->pool->lock, flags); + /* + * We could be printing a lot from atomic context, e.g. + * sysrq-t -> show_workqueue_state(). Avoid triggering + * hard lockup. + */ + touch_nmi_watchdog(); + } + } + + for_each_pool(pool, pi) { + struct worker *worker; + bool first = true; + + spin_lock_irqsave(&pool->lock, flags); + if (pool->nr_workers == pool->nr_idle) + goto next_pool; + + pr_info("pool %d:", pool->id); + pr_cont_pool_info(pool); + pr_cont(" hung=%us workers=%d", + jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000, + pool->nr_workers); + if (pool->manager) + pr_cont(" manager: %d", + task_pid_nr(pool->manager->task)); + list_for_each_entry(worker, &pool->idle_list, entry) { + pr_cont(" %s%d", first ? "idle: " : "", + task_pid_nr(worker->task)); + first = false; + } + pr_cont("\n"); + next_pool: + spin_unlock_irqrestore(&pool->lock, flags); + /* + * We could be printing a lot from atomic context, e.g. + * sysrq-t -> show_workqueue_state(). Avoid triggering + * hard lockup. + */ + touch_nmi_watchdog(); + } + + rcu_read_unlock_sched(); +} + +/* used to show worker information through /proc/PID/{comm,stat,status} */ +void wq_worker_comm(char *buf, size_t size, struct task_struct *task) +{ + int off; + + /* always show the actual comm */ + off = strscpy(buf, task->comm, size); + if (off < 0) + return; + + /* stabilize PF_WQ_WORKER and worker pool association */ + mutex_lock(&wq_pool_attach_mutex); + + if (task->flags & PF_WQ_WORKER) { + struct worker *worker = kthread_data(task); + struct worker_pool *pool = worker->pool; + + if (pool) { + spin_lock_irq(&pool->lock); + /* + * ->desc tracks information (wq name or + * set_worker_desc()) for the latest execution. If + * current, prepend '+', otherwise '-'. + */ + if (worker->desc[0] != '\0') { + if (worker->current_work) + scnprintf(buf + off, size - off, "+%s", + worker->desc); + else + scnprintf(buf + off, size - off, "-%s", + worker->desc); + } + spin_unlock_irq(&pool->lock); + } + } + + mutex_unlock(&wq_pool_attach_mutex); +} + +#ifdef CONFIG_SMP + +/* + * CPU hotplug. + * + * There are two challenges in supporting CPU hotplug. Firstly, there + * are a lot of assumptions on strong associations among work, pwq and + * pool which make migrating pending and scheduled works very + * difficult to implement without impacting hot paths. Secondly, + * worker pools serve mix of short, long and very long running works making + * blocked draining impractical. + * + * This is solved by allowing the pools to be disassociated from the CPU + * running as an unbound one and allowing it to be reattached later if the + * cpu comes back online. + */ + +static void unbind_workers(int cpu) +{ + struct worker_pool *pool; + struct worker *worker; + + for_each_cpu_worker_pool(pool, cpu) { + mutex_lock(&wq_pool_attach_mutex); + spin_lock_irq(&pool->lock); + + /* + * We've blocked all attach/detach operations. Make all workers + * unbound and set DISASSOCIATED. Before this, all workers + * except for the ones which are still executing works from + * before the last CPU down must be on the cpu. After + * this, they may become diasporas. + */ + for_each_pool_worker(worker, pool) + worker->flags |= WORKER_UNBOUND; + + pool->flags |= POOL_DISASSOCIATED; + + spin_unlock_irq(&pool->lock); + mutex_unlock(&wq_pool_attach_mutex); + + /* + * Call schedule() so that we cross rq->lock and thus can + * guarantee sched callbacks see the %WORKER_UNBOUND flag. + * This is necessary as scheduler callbacks may be invoked + * from other cpus. + */ + schedule(); + + /* + * Sched callbacks are disabled now. Zap nr_running. + * After this, nr_running stays zero and need_more_worker() + * and keep_working() are always true as long as the + * worklist is not empty. This pool now behaves as an + * unbound (in terms of concurrency management) pool which + * are served by workers tied to the pool. + */ + atomic_set(&pool->nr_running, 0); + + /* + * With concurrency management just turned off, a busy + * worker blocking could lead to lengthy stalls. Kick off + * unbound chain execution of currently pending work items. + */ + spin_lock_irq(&pool->lock); + wake_up_worker(pool); + spin_unlock_irq(&pool->lock); + } +} + +/** + * rebind_workers - rebind all workers of a pool to the associated CPU + * @pool: pool of interest + * + * @pool->cpu is coming online. Rebind all workers to the CPU. + */ +static void rebind_workers(struct worker_pool *pool) +{ + struct worker *worker; + + lockdep_assert_held(&wq_pool_attach_mutex); + + /* + * Restore CPU affinity of all workers. As all idle workers should + * be on the run-queue of the associated CPU before any local + * wake-ups for concurrency management happen, restore CPU affinity + * of all workers first and then clear UNBOUND. As we're called + * from CPU_ONLINE, the following shouldn't fail. + */ + for_each_pool_worker(worker, pool) + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, + pool->attrs->cpumask) < 0); + + spin_lock_irq(&pool->lock); + + pool->flags &= ~POOL_DISASSOCIATED; + + for_each_pool_worker(worker, pool) { + unsigned int worker_flags = worker->flags; + + /* + * A bound idle worker should actually be on the runqueue + * of the associated CPU for local wake-ups targeting it to + * work. Kick all idle workers so that they migrate to the + * associated CPU. Doing this in the same loop as + * replacing UNBOUND with REBOUND is safe as no worker will + * be bound before @pool->lock is released. + */ + if (worker_flags & WORKER_IDLE) + wake_up_process(worker->task); + + /* + * We want to clear UNBOUND but can't directly call + * worker_clr_flags() or adjust nr_running. Atomically + * replace UNBOUND with another NOT_RUNNING flag REBOUND. + * @worker will clear REBOUND using worker_clr_flags() when + * it initiates the next execution cycle thus restoring + * concurrency management. Note that when or whether + * @worker clears REBOUND doesn't affect correctness. + * + * WRITE_ONCE() is necessary because @worker->flags may be + * tested without holding any lock in + * wq_worker_waking_up(). Without it, NOT_RUNNING test may + * fail incorrectly leading to premature concurrency + * management operations. + */ + WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND)); + worker_flags |= WORKER_REBOUND; + worker_flags &= ~WORKER_UNBOUND; + WRITE_ONCE(worker->flags, worker_flags); + } + + spin_unlock_irq(&pool->lock); +} + +/** + * restore_unbound_workers_cpumask - restore cpumask of unbound workers + * @pool: unbound pool of interest + * @cpu: the CPU which is coming up + * + * An unbound pool may end up with a cpumask which doesn't have any online + * CPUs. When a worker of such pool get scheduled, the scheduler resets + * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any + * online CPU before, cpus_allowed of all its workers should be restored. + */ +static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) +{ + static cpumask_t cpumask; + struct worker *worker; + + lockdep_assert_held(&wq_pool_attach_mutex); + + /* is @cpu allowed for @pool? */ + if (!cpumask_test_cpu(cpu, pool->attrs->cpumask)) + return; + + cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask); + + /* as we're called from CPU_ONLINE, the following shouldn't fail */ + for_each_pool_worker(worker, pool) + WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0); +} + +int workqueue_prepare_cpu(unsigned int cpu) +{ + struct worker_pool *pool; + + for_each_cpu_worker_pool(pool, cpu) { + if (pool->nr_workers) + continue; + if (!create_worker(pool)) + return -ENOMEM; + } + return 0; +} + +int workqueue_online_cpu(unsigned int cpu) +{ + struct worker_pool *pool; + struct workqueue_struct *wq; + int pi; + + mutex_lock(&wq_pool_mutex); + + for_each_pool(pool, pi) { + mutex_lock(&wq_pool_attach_mutex); + + if (pool->cpu == cpu) + rebind_workers(pool); + else if (pool->cpu < 0) + restore_unbound_workers_cpumask(pool, cpu); + + mutex_unlock(&wq_pool_attach_mutex); + } + + /* update NUMA affinity of unbound workqueues */ + list_for_each_entry(wq, &workqueues, list) + wq_update_unbound_numa(wq, cpu, true); + + mutex_unlock(&wq_pool_mutex); + return 0; +} + +int workqueue_offline_cpu(unsigned int cpu) +{ + struct workqueue_struct *wq; + + /* unbinding per-cpu workers should happen on the local CPU */ + if (WARN_ON(cpu != smp_processor_id())) + return -1; + + unbind_workers(cpu); + + /* update NUMA affinity of unbound workqueues */ + mutex_lock(&wq_pool_mutex); + list_for_each_entry(wq, &workqueues, list) + wq_update_unbound_numa(wq, cpu, false); + mutex_unlock(&wq_pool_mutex); + + return 0; +} + +struct work_for_cpu { + struct work_struct work; + long (*fn)(void *); + void *arg; + long ret; +}; + +static void work_for_cpu_fn(struct work_struct *work) +{ + struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work); + + wfc->ret = wfc->fn(wfc->arg); +} + +/** + * work_on_cpu - run a function in thread context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function arg + * + * It is up to the caller to ensure that the cpu doesn't go offline. + * The caller must not hold any locks which would prevent @fn from completing. + * + * Return: The value @fn returns. + */ +long work_on_cpu(int cpu, long (*fn)(void *), void *arg) +{ + struct work_for_cpu wfc = { .fn = fn, .arg = arg }; + + INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn); + schedule_work_on(cpu, &wfc.work); + flush_work(&wfc.work); + destroy_work_on_stack(&wfc.work); + return wfc.ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu); + +/** + * work_on_cpu_safe - run a function in thread context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function argument + * + * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold + * any locks which would prevent @fn from completing. + * + * Return: The value @fn returns. + */ +long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg) +{ + long ret = -ENODEV; + + get_online_cpus(); + if (cpu_online(cpu)) + ret = work_on_cpu(cpu, fn, arg); + put_online_cpus(); + return ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu_safe); +#endif /* CONFIG_SMP */ + +#ifdef CONFIG_FREEZER + +/** + * freeze_workqueues_begin - begin freezing workqueues + * + * Start freezing workqueues. After this function returns, all freezable + * workqueues will queue new works to their delayed_works list instead of + * pool->worklist. + * + * CONTEXT: + * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's. + */ +void freeze_workqueues_begin(void) +{ + struct workqueue_struct *wq; + struct pool_workqueue *pwq; + + mutex_lock(&wq_pool_mutex); + + WARN_ON_ONCE(workqueue_freezing); + workqueue_freezing = true; + + list_for_each_entry(wq, &workqueues, list) { + mutex_lock(&wq->mutex); + for_each_pwq(pwq, wq) + pwq_adjust_max_active(pwq); + mutex_unlock(&wq->mutex); + } + + mutex_unlock(&wq_pool_mutex); +} + +/** + * freeze_workqueues_busy - are freezable workqueues still busy? + * + * Check whether freezing is complete. This function must be called + * between freeze_workqueues_begin() and thaw_workqueues(). + * + * CONTEXT: + * Grabs and releases wq_pool_mutex. + * + * Return: + * %true if some freezable workqueues are still busy. %false if freezing + * is complete. + */ +bool freeze_workqueues_busy(void) +{ + bool busy = false; + struct workqueue_struct *wq; + struct pool_workqueue *pwq; + + mutex_lock(&wq_pool_mutex); + + WARN_ON_ONCE(!workqueue_freezing); + + list_for_each_entry(wq, &workqueues, list) { + if (!(wq->flags & WQ_FREEZABLE)) + continue; + /* + * nr_active is monotonically decreasing. It's safe + * to peek without lock. + */ + rcu_read_lock_sched(); + for_each_pwq(pwq, wq) { + WARN_ON_ONCE(pwq->nr_active < 0); + if (pwq->nr_active) { + busy = true; + rcu_read_unlock_sched(); + goto out_unlock; + } + } + rcu_read_unlock_sched(); + } +out_unlock: + mutex_unlock(&wq_pool_mutex); + return busy; +} + +/** + * thaw_workqueues - thaw workqueues + * + * Thaw workqueues. Normal queueing is restored and all collected + * frozen works are transferred to their respective pool worklists. + * + * CONTEXT: + * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's. + */ +void thaw_workqueues(void) +{ + struct workqueue_struct *wq; + struct pool_workqueue *pwq; + + mutex_lock(&wq_pool_mutex); + + if (!workqueue_freezing) + goto out_unlock; + + workqueue_freezing = false; + + /* restore max_active and repopulate worklist */ + list_for_each_entry(wq, &workqueues, list) { + mutex_lock(&wq->mutex); + for_each_pwq(pwq, wq) + pwq_adjust_max_active(pwq); + mutex_unlock(&wq->mutex); + } + +out_unlock: + mutex_unlock(&wq_pool_mutex); +} +#endif /* CONFIG_FREEZER */ + +static int workqueue_apply_unbound_cpumask(void) +{ + LIST_HEAD(ctxs); + int ret = 0; + struct workqueue_struct *wq; + struct apply_wqattrs_ctx *ctx, *n; + + lockdep_assert_held(&wq_pool_mutex); + + list_for_each_entry(wq, &workqueues, list) { + if (!(wq->flags & WQ_UNBOUND)) + continue; + /* creating multiple pwqs breaks ordering guarantee */ + if (wq->flags & __WQ_ORDERED) + continue; + + ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs); + if (!ctx) { + ret = -ENOMEM; + break; + } + + list_add_tail(&ctx->list, &ctxs); + } + + list_for_each_entry_safe(ctx, n, &ctxs, list) { + if (!ret) + apply_wqattrs_commit(ctx); + apply_wqattrs_cleanup(ctx); + } + + return ret; +} + +/** + * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask + * @cpumask: the cpumask to set + * + * The low-level workqueues cpumask is a global cpumask that limits + * the affinity of all unbound workqueues. This function check the @cpumask + * and apply it to all unbound workqueues and updates all pwqs of them. + * + * Retun: 0 - Success + * -EINVAL - Invalid @cpumask + * -ENOMEM - Failed to allocate memory for attrs or pwqs. + */ +int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) +{ + int ret = -EINVAL; + cpumask_var_t saved_cpumask; + + /* + * Not excluding isolated cpus on purpose. + * If the user wishes to include them, we allow that. + */ + cpumask_and(cpumask, cpumask, cpu_possible_mask); + if (!cpumask_empty(cpumask)) { + apply_wqattrs_lock(); + if (cpumask_equal(cpumask, wq_unbound_cpumask)) { + ret = 0; + goto out_unlock; + } + + if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) { + ret = -ENOMEM; + goto out_unlock; + } + + /* save the old wq_unbound_cpumask. */ + cpumask_copy(saved_cpumask, wq_unbound_cpumask); + + /* update wq_unbound_cpumask at first and apply it to wqs. */ + cpumask_copy(wq_unbound_cpumask, cpumask); + ret = workqueue_apply_unbound_cpumask(); + + /* restore the wq_unbound_cpumask when failed. */ + if (ret < 0) + cpumask_copy(wq_unbound_cpumask, saved_cpumask); + + free_cpumask_var(saved_cpumask); +out_unlock: + apply_wqattrs_unlock(); + } + + return ret; +} + +#ifdef CONFIG_SYSFS +/* + * Workqueues with WQ_SYSFS flag set is visible to userland via + * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the + * following attributes. + * + * per_cpu RO bool : whether the workqueue is per-cpu or unbound + * max_active RW int : maximum number of in-flight work items + * + * Unbound workqueues have the following extra attributes. + * + * pool_ids RO int : the associated pool IDs for each node + * nice RW int : nice value of the workers + * cpumask RW mask : bitmask of allowed CPUs for the workers + * numa RW bool : whether enable NUMA affinity + */ +struct wq_device { + struct workqueue_struct *wq; + struct device dev; +}; + +static struct workqueue_struct *dev_to_wq(struct device *dev) +{ + struct wq_device *wq_dev = container_of(dev, struct wq_device, dev); + + return wq_dev->wq; +} + +static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + + return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND)); +} +static DEVICE_ATTR_RO(per_cpu); + +static ssize_t max_active_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + + return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active); +} + +static ssize_t max_active_store(struct device *dev, + struct device_attribute *attr, const char *buf, + size_t count) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + int val; + + if (sscanf(buf, "%d", &val) != 1 || val <= 0) + return -EINVAL; + + workqueue_set_max_active(wq, val); + return count; +} +static DEVICE_ATTR_RW(max_active); + +static struct attribute *wq_sysfs_attrs[] = { + &dev_attr_per_cpu.attr, + &dev_attr_max_active.attr, + NULL, +}; +ATTRIBUTE_GROUPS(wq_sysfs); + +static ssize_t wq_pool_ids_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + const char *delim = ""; + int node, written = 0; + + rcu_read_lock_sched(); + for_each_node(node) { + written += scnprintf(buf + written, PAGE_SIZE - written, + "%s%d:%d", delim, node, + unbound_pwq_by_node(wq, node)->pool->id); + delim = " "; + } + written += scnprintf(buf + written, PAGE_SIZE - written, "\n"); + rcu_read_unlock_sched(); + + return written; +} + +static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + int written; + + mutex_lock(&wq->mutex); + written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice); + mutex_unlock(&wq->mutex); + + return written; +} + +/* prepare workqueue_attrs for sysfs store operations */ +static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq) +{ + struct workqueue_attrs *attrs; + + lockdep_assert_held(&wq_pool_mutex); + + attrs = alloc_workqueue_attrs(GFP_KERNEL); + if (!attrs) + return NULL; + + copy_workqueue_attrs(attrs, wq->unbound_attrs); + return attrs; +} + +static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + struct workqueue_attrs *attrs; + int ret = -ENOMEM; + + apply_wqattrs_lock(); + + attrs = wq_sysfs_prep_attrs(wq); + if (!attrs) + goto out_unlock; + + if (sscanf(buf, "%d", &attrs->nice) == 1 && + attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE) + ret = apply_workqueue_attrs_locked(wq, attrs); + else + ret = -EINVAL; + +out_unlock: + apply_wqattrs_unlock(); + free_workqueue_attrs(attrs); + return ret ?: count; +} + +static ssize_t wq_cpumask_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + int written; + + mutex_lock(&wq->mutex); + written = scnprintf(buf, PAGE_SIZE, "%*pb\n", + cpumask_pr_args(wq->unbound_attrs->cpumask)); + mutex_unlock(&wq->mutex); + return written; +} + +static ssize_t wq_cpumask_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + struct workqueue_attrs *attrs; + int ret = -ENOMEM; + + apply_wqattrs_lock(); + + attrs = wq_sysfs_prep_attrs(wq); + if (!attrs) + goto out_unlock; + + ret = cpumask_parse(buf, attrs->cpumask); + if (!ret) + ret = apply_workqueue_attrs_locked(wq, attrs); + +out_unlock: + apply_wqattrs_unlock(); + free_workqueue_attrs(attrs); + return ret ?: count; +} + +static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + int written; + + mutex_lock(&wq->mutex); + written = scnprintf(buf, PAGE_SIZE, "%d\n", + !wq->unbound_attrs->no_numa); + mutex_unlock(&wq->mutex); + + return written; +} + +static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct workqueue_struct *wq = dev_to_wq(dev); + struct workqueue_attrs *attrs; + int v, ret = -ENOMEM; + + apply_wqattrs_lock(); + + attrs = wq_sysfs_prep_attrs(wq); + if (!attrs) + goto out_unlock; + + ret = -EINVAL; + if (sscanf(buf, "%d", &v) == 1) { + attrs->no_numa = !v; + ret = apply_workqueue_attrs_locked(wq, attrs); + } + +out_unlock: + apply_wqattrs_unlock(); + free_workqueue_attrs(attrs); + return ret ?: count; +} + +static struct device_attribute wq_sysfs_unbound_attrs[] = { + __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL), + __ATTR(nice, 0644, wq_nice_show, wq_nice_store), + __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store), + __ATTR(numa, 0644, wq_numa_show, wq_numa_store), + __ATTR_NULL, +}; + +static struct bus_type wq_subsys = { + .name = "workqueue", + .dev_groups = wq_sysfs_groups, +}; + +static ssize_t wq_unbound_cpumask_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + int written; + + mutex_lock(&wq_pool_mutex); + written = scnprintf(buf, PAGE_SIZE, "%*pb\n", + cpumask_pr_args(wq_unbound_cpumask)); + mutex_unlock(&wq_pool_mutex); + + return written; +} + +static ssize_t wq_unbound_cpumask_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + cpumask_var_t cpumask; + int ret; + + if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + ret = cpumask_parse(buf, cpumask); + if (!ret) + ret = workqueue_set_unbound_cpumask(cpumask); + + free_cpumask_var(cpumask); + return ret ? ret : count; +} + +static struct device_attribute wq_sysfs_cpumask_attr = + __ATTR(cpumask, 0644, wq_unbound_cpumask_show, + wq_unbound_cpumask_store); + +static int __init wq_sysfs_init(void) +{ + int err; + + err = subsys_virtual_register(&wq_subsys, NULL); + if (err) + return err; + + return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr); +} +core_initcall(wq_sysfs_init); + +static void wq_device_release(struct device *dev) +{ + struct wq_device *wq_dev = container_of(dev, struct wq_device, dev); + + kfree(wq_dev); +} + +/** + * workqueue_sysfs_register - make a workqueue visible in sysfs + * @wq: the workqueue to register + * + * Expose @wq in sysfs under /sys/bus/workqueue/devices. + * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set + * which is the preferred method. + * + * Workqueue user should use this function directly iff it wants to apply + * workqueue_attrs before making the workqueue visible in sysfs; otherwise, + * apply_workqueue_attrs() may race against userland updating the + * attributes. + * + * Return: 0 on success, -errno on failure. + */ +int workqueue_sysfs_register(struct workqueue_struct *wq) +{ + struct wq_device *wq_dev; + int ret; + + /* + * Adjusting max_active or creating new pwqs by applying + * attributes breaks ordering guarantee. Disallow exposing ordered + * workqueues. + */ + if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT)) + return -EINVAL; + + wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL); + if (!wq_dev) + return -ENOMEM; + + wq_dev->wq = wq; + wq_dev->dev.bus = &wq_subsys; + wq_dev->dev.release = wq_device_release; + dev_set_name(&wq_dev->dev, "%s", wq->name); + + /* + * unbound_attrs are created separately. Suppress uevent until + * everything is ready. + */ + dev_set_uevent_suppress(&wq_dev->dev, true); + + ret = device_register(&wq_dev->dev); + if (ret) { + put_device(&wq_dev->dev); + wq->wq_dev = NULL; + return ret; + } + + if (wq->flags & WQ_UNBOUND) { + struct device_attribute *attr; + + for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) { + ret = device_create_file(&wq_dev->dev, attr); + if (ret) { + device_unregister(&wq_dev->dev); + wq->wq_dev = NULL; + return ret; + } + } + } + + dev_set_uevent_suppress(&wq_dev->dev, false); + kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD); + return 0; +} + +/** + * workqueue_sysfs_unregister - undo workqueue_sysfs_register() + * @wq: the workqueue to unregister + * + * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister. + */ +static void workqueue_sysfs_unregister(struct workqueue_struct *wq) +{ + struct wq_device *wq_dev = wq->wq_dev; + + if (!wq->wq_dev) + return; + + wq->wq_dev = NULL; + device_unregister(&wq_dev->dev); +} +#else /* CONFIG_SYSFS */ +static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { } +#endif /* CONFIG_SYSFS */ + +/* + * Workqueue watchdog. + * + * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal + * flush dependency, a concurrency managed work item which stays RUNNING + * indefinitely. Workqueue stalls can be very difficult to debug as the + * usual warning mechanisms don't trigger and internal workqueue state is + * largely opaque. + * + * Workqueue watchdog monitors all worker pools periodically and dumps + * state if some pools failed to make forward progress for a while where + * forward progress is defined as the first item on ->worklist changing. + * + * This mechanism is controlled through the kernel parameter + * "workqueue.watchdog_thresh" which can be updated at runtime through the + * corresponding sysfs parameter file. + */ +#ifdef CONFIG_WQ_WATCHDOG + +static unsigned long wq_watchdog_thresh = 30; +static struct timer_list wq_watchdog_timer; + +static unsigned long wq_watchdog_touched = INITIAL_JIFFIES; +static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES; + +static void wq_watchdog_reset_touched(void) +{ + int cpu; + + wq_watchdog_touched = jiffies; + for_each_possible_cpu(cpu) + per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies; +} + +static void wq_watchdog_timer_fn(struct timer_list *unused) +{ + unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ; + bool lockup_detected = false; + unsigned long now = jiffies; + struct worker_pool *pool; + int pi; + + if (!thresh) + return; + + rcu_read_lock(); + + for_each_pool(pool, pi) { + unsigned long pool_ts, touched, ts; + + if (list_empty(&pool->worklist)) + continue; + + /* + * If a virtual machine is stopped by the host it can look to + * the watchdog like a stall. + */ + kvm_check_and_clear_guest_paused(); + + /* get the latest of pool and touched timestamps */ + pool_ts = READ_ONCE(pool->watchdog_ts); + touched = READ_ONCE(wq_watchdog_touched); + + if (time_after(pool_ts, touched)) + ts = pool_ts; + else + ts = touched; + + if (pool->cpu >= 0) { + unsigned long cpu_touched = + READ_ONCE(per_cpu(wq_watchdog_touched_cpu, + pool->cpu)); + if (time_after(cpu_touched, ts)) + ts = cpu_touched; + } + + /* did we stall? */ + if (time_after(now, ts + thresh)) { + lockup_detected = true; + pr_emerg("BUG: workqueue lockup - pool"); + pr_cont_pool_info(pool); + pr_cont(" stuck for %us!\n", + jiffies_to_msecs(now - pool_ts) / 1000); + } + } + + rcu_read_unlock(); + + if (lockup_detected) + show_workqueue_state(); + + wq_watchdog_reset_touched(); + mod_timer(&wq_watchdog_timer, jiffies + thresh); +} + +notrace void wq_watchdog_touch(int cpu) +{ + if (cpu >= 0) + per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies; + else + wq_watchdog_touched = jiffies; +} + +static void wq_watchdog_set_thresh(unsigned long thresh) +{ + wq_watchdog_thresh = 0; + del_timer_sync(&wq_watchdog_timer); + + if (thresh) { + wq_watchdog_thresh = thresh; + wq_watchdog_reset_touched(); + mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ); + } +} + +static int wq_watchdog_param_set_thresh(const char *val, + const struct kernel_param *kp) +{ + unsigned long thresh; + int ret; + + ret = kstrtoul(val, 0, &thresh); + if (ret) + return ret; + + if (system_wq) + wq_watchdog_set_thresh(thresh); + else + wq_watchdog_thresh = thresh; + + return 0; +} + +static const struct kernel_param_ops wq_watchdog_thresh_ops = { + .set = wq_watchdog_param_set_thresh, + .get = param_get_ulong, +}; + +module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh, + 0644); + +static void wq_watchdog_init(void) +{ + timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE); + wq_watchdog_set_thresh(wq_watchdog_thresh); +} + +#else /* CONFIG_WQ_WATCHDOG */ + +static inline void wq_watchdog_init(void) { } + +#endif /* CONFIG_WQ_WATCHDOG */ + +static void __init wq_numa_init(void) +{ + cpumask_var_t *tbl; + int node, cpu; + + if (num_possible_nodes() <= 1) + return; + + if (wq_disable_numa) { + pr_info("workqueue: NUMA affinity support disabled\n"); + return; + } + + wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL); + BUG_ON(!wq_update_unbound_numa_attrs_buf); + + /* + * We want masks of possible CPUs of each node which isn't readily + * available. Build one from cpu_to_node() which should have been + * fully initialized by now. + */ + tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL); + BUG_ON(!tbl); + + for_each_node(node) + BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL, + node_online(node) ? node : NUMA_NO_NODE)); + + for_each_possible_cpu(cpu) { + node = cpu_to_node(cpu); + if (WARN_ON(node == NUMA_NO_NODE)) { + pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu); + /* happens iff arch is bonkers, let's just proceed */ + return; + } + cpumask_set_cpu(cpu, tbl[node]); + } + + wq_numa_possible_cpumask = tbl; + wq_numa_enabled = true; +} + +/** + * workqueue_init_early - early init for workqueue subsystem + * + * This is the first half of two-staged workqueue subsystem initialization + * and invoked as soon as the bare basics - memory allocation, cpumasks and + * idr are up. It sets up all the data structures and system workqueues + * and allows early boot code to create workqueues and queue/cancel work + * items. Actual work item execution starts only after kthreads can be + * created and scheduled right before early initcalls. + */ +int __init workqueue_init_early(void) +{ + int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL }; + int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ; + int i, cpu; + + WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long)); + + BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL)); + cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags)); + + pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC); + + /* initialize CPU pools */ + for_each_possible_cpu(cpu) { + struct worker_pool *pool; + + i = 0; + for_each_cpu_worker_pool(pool, cpu) { + BUG_ON(init_worker_pool(pool)); + pool->cpu = cpu; + cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu)); + pool->attrs->nice = std_nice[i++]; + pool->node = cpu_to_node(cpu); + + /* alloc pool ID */ + mutex_lock(&wq_pool_mutex); + BUG_ON(worker_pool_assign_id(pool)); + mutex_unlock(&wq_pool_mutex); + } + } + + /* create default unbound and ordered wq attrs */ + for (i = 0; i < NR_STD_WORKER_POOLS; i++) { + struct workqueue_attrs *attrs; + + BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL))); + attrs->nice = std_nice[i]; + unbound_std_wq_attrs[i] = attrs; + + /* + * An ordered wq should have only one pwq as ordering is + * guaranteed by max_active which is enforced by pwqs. + * Turn off NUMA so that dfl_pwq is used for all nodes. + */ + BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL))); + attrs->nice = std_nice[i]; + attrs->no_numa = true; + ordered_wq_attrs[i] = attrs; + } + + system_wq = alloc_workqueue("events", 0, 0); + system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0); + system_long_wq = alloc_workqueue("events_long", 0, 0); + system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, + WQ_UNBOUND_MAX_ACTIVE); + system_freezable_wq = alloc_workqueue("events_freezable", + WQ_FREEZABLE, 0); + system_power_efficient_wq = alloc_workqueue("events_power_efficient", + WQ_POWER_EFFICIENT, 0); + system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient", + WQ_FREEZABLE | WQ_POWER_EFFICIENT, + 0); + BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq || + !system_unbound_wq || !system_freezable_wq || + !system_power_efficient_wq || + !system_freezable_power_efficient_wq); + + return 0; +} + +/** + * workqueue_init - bring workqueue subsystem fully online + * + * This is the latter half of two-staged workqueue subsystem initialization + * and invoked as soon as kthreads can be created and scheduled. + * Workqueues have been created and work items queued on them, but there + * are no kworkers executing the work items yet. Populate the worker pools + * with the initial workers and enable future kworker creations. + */ +int __init workqueue_init(void) +{ + struct workqueue_struct *wq; + struct worker_pool *pool; + int cpu, bkt; + + /* + * It'd be simpler to initialize NUMA in workqueue_init_early() but + * CPU to node mapping may not be available that early on some + * archs such as power and arm64. As per-cpu pools created + * previously could be missing node hint and unbound pools NUMA + * affinity, fix them up. + * + * Also, while iterating workqueues, create rescuers if requested. + */ + wq_numa_init(); + + mutex_lock(&wq_pool_mutex); + + for_each_possible_cpu(cpu) { + for_each_cpu_worker_pool(pool, cpu) { + pool->node = cpu_to_node(cpu); + } + } + + list_for_each_entry(wq, &workqueues, list) { + wq_update_unbound_numa(wq, smp_processor_id(), true); + WARN(init_rescuer(wq), + "workqueue: failed to create early rescuer for %s", + wq->name); + } + + mutex_unlock(&wq_pool_mutex); + + /* create the initial workers */ + for_each_online_cpu(cpu) { + for_each_cpu_worker_pool(pool, cpu) { + pool->flags &= ~POOL_DISASSOCIATED; + BUG_ON(!create_worker(pool)); + } + } + + hash_for_each(unbound_pool_hash, bkt, pool, hash_node) + BUG_ON(!create_worker(pool)); + + wq_online = true; + wq_watchdog_init(); + + return 0; +} |