diff options
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 2409 |
1 files changed, 2409 insertions, 0 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c new file mode 100644 index 000000000..c9ca190ec --- /dev/null +++ b/kernel/cpu.c @@ -0,0 +1,2409 @@ +/* CPU control. + * (C) 2001, 2002, 2003, 2004 Rusty Russell + * + * This code is licenced under the GPL. + */ +#include <linux/sched/mm.h> +#include <linux/proc_fs.h> +#include <linux/smp.h> +#include <linux/init.h> +#include <linux/notifier.h> +#include <linux/sched/signal.h> +#include <linux/sched/hotplug.h> +#include <linux/sched/task.h> +#include <linux/sched/smt.h> +#include <linux/unistd.h> +#include <linux/cpu.h> +#include <linux/oom.h> +#include <linux/rcupdate.h> +#include <linux/export.h> +#include <linux/bug.h> +#include <linux/kthread.h> +#include <linux/stop_machine.h> +#include <linux/mutex.h> +#include <linux/gfp.h> +#include <linux/suspend.h> +#include <linux/lockdep.h> +#include <linux/tick.h> +#include <linux/irq.h> +#include <linux/nmi.h> +#include <linux/smpboot.h> +#include <linux/relay.h> +#include <linux/slab.h> +#include <linux/percpu-rwsem.h> +#include <linux/cpuset.h> +#include <linux/random.h> + +#include <trace/events/power.h> +#define CREATE_TRACE_POINTS +#include <trace/events/cpuhp.h> + +#include "smpboot.h" + +/** + * cpuhp_cpu_state - Per cpu hotplug state storage + * @state: The current cpu state + * @target: The target state + * @thread: Pointer to the hotplug thread + * @should_run: Thread should execute + * @rollback: Perform a rollback + * @single: Single callback invocation + * @bringup: Single callback bringup or teardown selector + * @cb_state: The state for a single callback (install/uninstall) + * @result: Result of the operation + * @done_up: Signal completion to the issuer of the task for cpu-up + * @done_down: Signal completion to the issuer of the task for cpu-down + */ +struct cpuhp_cpu_state { + enum cpuhp_state state; + enum cpuhp_state target; + enum cpuhp_state fail; +#ifdef CONFIG_SMP + struct task_struct *thread; + bool should_run; + bool rollback; + bool single; + bool bringup; + bool booted_once; + struct hlist_node *node; + struct hlist_node *last; + enum cpuhp_state cb_state; + int result; + struct completion done_up; + struct completion done_down; +#endif +}; + +static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = { + .fail = CPUHP_INVALID, +}; + +#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP) +static struct lockdep_map cpuhp_state_up_map = + STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map); +static struct lockdep_map cpuhp_state_down_map = + STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map); + + +static inline void cpuhp_lock_acquire(bool bringup) +{ + lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map); +} + +static inline void cpuhp_lock_release(bool bringup) +{ + lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map); +} +#else + +static inline void cpuhp_lock_acquire(bool bringup) { } +static inline void cpuhp_lock_release(bool bringup) { } + +#endif + +/** + * cpuhp_step - Hotplug state machine step + * @name: Name of the step + * @startup: Startup function of the step + * @teardown: Teardown function of the step + * @cant_stop: Bringup/teardown can't be stopped at this step + */ +struct cpuhp_step { + const char *name; + union { + int (*single)(unsigned int cpu); + int (*multi)(unsigned int cpu, + struct hlist_node *node); + } startup; + union { + int (*single)(unsigned int cpu); + int (*multi)(unsigned int cpu, + struct hlist_node *node); + } teardown; + struct hlist_head list; + bool cant_stop; + bool multi_instance; +}; + +static DEFINE_MUTEX(cpuhp_state_mutex); +static struct cpuhp_step cpuhp_hp_states[]; + +static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state) +{ + return cpuhp_hp_states + state; +} + +/** + * cpuhp_invoke_callback _ Invoke the callbacks for a given state + * @cpu: The cpu for which the callback should be invoked + * @state: The state to do callbacks for + * @bringup: True if the bringup callback should be invoked + * @node: For multi-instance, do a single entry callback for install/remove + * @lastp: For multi-instance rollback, remember how far we got + * + * Called from cpu hotplug and from the state register machinery. + */ +static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, + bool bringup, struct hlist_node *node, + struct hlist_node **lastp) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + struct cpuhp_step *step = cpuhp_get_step(state); + int (*cbm)(unsigned int cpu, struct hlist_node *node); + int (*cb)(unsigned int cpu); + int ret, cnt; + + if (st->fail == state) { + st->fail = CPUHP_INVALID; + + if (!(bringup ? step->startup.single : step->teardown.single)) + return 0; + + return -EAGAIN; + } + + if (!step->multi_instance) { + WARN_ON_ONCE(lastp && *lastp); + cb = bringup ? step->startup.single : step->teardown.single; + if (!cb) + return 0; + trace_cpuhp_enter(cpu, st->target, state, cb); + ret = cb(cpu); + trace_cpuhp_exit(cpu, st->state, state, ret); + return ret; + } + cbm = bringup ? step->startup.multi : step->teardown.multi; + if (!cbm) + return 0; + + /* Single invocation for instance add/remove */ + if (node) { + WARN_ON_ONCE(lastp && *lastp); + trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node); + ret = cbm(cpu, node); + trace_cpuhp_exit(cpu, st->state, state, ret); + return ret; + } + + /* State transition. Invoke on all instances */ + cnt = 0; + hlist_for_each(node, &step->list) { + if (lastp && node == *lastp) + break; + + trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node); + ret = cbm(cpu, node); + trace_cpuhp_exit(cpu, st->state, state, ret); + if (ret) { + if (!lastp) + goto err; + + *lastp = node; + return ret; + } + cnt++; + } + if (lastp) + *lastp = NULL; + return 0; +err: + /* Rollback the instances if one failed */ + cbm = !bringup ? step->startup.multi : step->teardown.multi; + if (!cbm) + return ret; + + hlist_for_each(node, &step->list) { + if (!cnt--) + break; + + trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node); + ret = cbm(cpu, node); + trace_cpuhp_exit(cpu, st->state, state, ret); + /* + * Rollback must not fail, + */ + WARN_ON_ONCE(ret); + } + return ret; +} + +#ifdef CONFIG_SMP +static bool cpuhp_is_ap_state(enum cpuhp_state state) +{ + /* + * The extra check for CPUHP_TEARDOWN_CPU is only for documentation + * purposes as that state is handled explicitly in cpu_down. + */ + return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU; +} + +static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup) +{ + struct completion *done = bringup ? &st->done_up : &st->done_down; + wait_for_completion(done); +} + +static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup) +{ + struct completion *done = bringup ? &st->done_up : &st->done_down; + complete(done); +} + +/* + * The former STARTING/DYING states, ran with IRQs disabled and must not fail. + */ +static bool cpuhp_is_atomic_state(enum cpuhp_state state) +{ + return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE; +} + +/* Serializes the updates to cpu_online_mask, cpu_present_mask */ +static DEFINE_MUTEX(cpu_add_remove_lock); +bool cpuhp_tasks_frozen; +EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen); + +/* + * The following two APIs (cpu_maps_update_begin/done) must be used when + * attempting to serialize the updates to cpu_online_mask & cpu_present_mask. + */ +void cpu_maps_update_begin(void) +{ + mutex_lock(&cpu_add_remove_lock); +} + +void cpu_maps_update_done(void) +{ + mutex_unlock(&cpu_add_remove_lock); +} + +/* + * If set, cpu_up and cpu_down will return -EBUSY and do nothing. + * Should always be manipulated under cpu_add_remove_lock + */ +static int cpu_hotplug_disabled; + +#ifdef CONFIG_HOTPLUG_CPU + +DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock); + +void cpus_read_lock(void) +{ + percpu_down_read(&cpu_hotplug_lock); +} +EXPORT_SYMBOL_GPL(cpus_read_lock); + +int cpus_read_trylock(void) +{ + return percpu_down_read_trylock(&cpu_hotplug_lock); +} +EXPORT_SYMBOL_GPL(cpus_read_trylock); + +void cpus_read_unlock(void) +{ + percpu_up_read(&cpu_hotplug_lock); +} +EXPORT_SYMBOL_GPL(cpus_read_unlock); + +void cpus_write_lock(void) +{ + percpu_down_write(&cpu_hotplug_lock); +} + +void cpus_write_unlock(void) +{ + percpu_up_write(&cpu_hotplug_lock); +} + +void lockdep_assert_cpus_held(void) +{ + /* + * We can't have hotplug operations before userspace starts running, + * and some init codepaths will knowingly not take the hotplug lock. + * This is all valid, so mute lockdep until it makes sense to report + * unheld locks. + */ + if (system_state < SYSTEM_RUNNING) + return; + + percpu_rwsem_assert_held(&cpu_hotplug_lock); +} + +/* + * Wait for currently running CPU hotplug operations to complete (if any) and + * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects + * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the + * hotplug path before performing hotplug operations. So acquiring that lock + * guarantees mutual exclusion from any currently running hotplug operations. + */ +void cpu_hotplug_disable(void) +{ + cpu_maps_update_begin(); + cpu_hotplug_disabled++; + cpu_maps_update_done(); +} +EXPORT_SYMBOL_GPL(cpu_hotplug_disable); + +static void __cpu_hotplug_enable(void) +{ + if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n")) + return; + cpu_hotplug_disabled--; +} + +void cpu_hotplug_enable(void) +{ + cpu_maps_update_begin(); + __cpu_hotplug_enable(); + cpu_maps_update_done(); +} +EXPORT_SYMBOL_GPL(cpu_hotplug_enable); +#endif /* CONFIG_HOTPLUG_CPU */ + +/* + * Architectures that need SMT-specific errata handling during SMT hotplug + * should override this. + */ +void __weak arch_smt_update(void) { } + +#ifdef CONFIG_HOTPLUG_SMT +enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED; + +void __init cpu_smt_disable(bool force) +{ + if (cpu_smt_control == CPU_SMT_FORCE_DISABLED || + cpu_smt_control == CPU_SMT_NOT_SUPPORTED) + return; + + if (force) { + pr_info("SMT: Force disabled\n"); + cpu_smt_control = CPU_SMT_FORCE_DISABLED; + } else { + pr_info("SMT: disabled\n"); + cpu_smt_control = CPU_SMT_DISABLED; + } +} + +/* + * The decision whether SMT is supported can only be done after the full + * CPU identification. Called from architecture code. + */ +void __init cpu_smt_check_topology(void) +{ + if (!topology_smt_supported()) + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; +} + +static int __init smt_cmdline_disable(char *str) +{ + cpu_smt_disable(str && !strcmp(str, "force")); + return 0; +} +early_param("nosmt", smt_cmdline_disable); + +static inline bool cpu_smt_allowed(unsigned int cpu) +{ + if (cpu_smt_control == CPU_SMT_ENABLED) + return true; + + if (topology_is_primary_thread(cpu)) + return true; + + /* + * On x86 it's required to boot all logical CPUs at least once so + * that the init code can get a chance to set CR4.MCE on each + * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any + * core will shutdown the machine. + */ + return !per_cpu(cpuhp_state, cpu).booted_once; +} +#else +static inline bool cpu_smt_allowed(unsigned int cpu) { return true; } +#endif + +static inline enum cpuhp_state +cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target) +{ + enum cpuhp_state prev_state = st->state; + + st->rollback = false; + st->last = NULL; + + st->target = target; + st->single = false; + st->bringup = st->state < target; + + return prev_state; +} + +static inline void +cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state) +{ + st->rollback = true; + + /* + * If we have st->last we need to undo partial multi_instance of this + * state first. Otherwise start undo at the previous state. + */ + if (!st->last) { + if (st->bringup) + st->state--; + else + st->state++; + } + + st->target = prev_state; + st->bringup = !st->bringup; +} + +/* Regular hotplug invocation of the AP hotplug thread */ +static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st) +{ + if (!st->single && st->state == st->target) + return; + + st->result = 0; + /* + * Make sure the above stores are visible before should_run becomes + * true. Paired with the mb() above in cpuhp_thread_fun() + */ + smp_mb(); + st->should_run = true; + wake_up_process(st->thread); + wait_for_ap_thread(st, st->bringup); +} + +static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target) +{ + enum cpuhp_state prev_state; + int ret; + + prev_state = cpuhp_set_state(st, target); + __cpuhp_kick_ap(st); + if ((ret = st->result)) { + cpuhp_reset_state(st, prev_state); + __cpuhp_kick_ap(st); + } + + return ret; +} + +static int bringup_wait_for_ap(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + + /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */ + wait_for_ap_thread(st, true); + if (WARN_ON_ONCE((!cpu_online(cpu)))) + return -ECANCELED; + + /* Unpark the hotplug thread of the target cpu */ + kthread_unpark(st->thread); + + /* + * SMT soft disabling on X86 requires to bring the CPU out of the + * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The + * CPU marked itself as booted_once in cpu_notify_starting() so the + * cpu_smt_allowed() check will now return false if this is not the + * primary sibling. + */ + if (!cpu_smt_allowed(cpu)) + return -ECANCELED; + + if (st->target <= CPUHP_AP_ONLINE_IDLE) + return 0; + + return cpuhp_kick_ap(st, st->target); +} + +static int bringup_cpu(unsigned int cpu) +{ + struct task_struct *idle = idle_thread_get(cpu); + int ret; + + /* + * Some architectures have to walk the irq descriptors to + * setup the vector space for the cpu which comes online. + * Prevent irq alloc/free across the bringup. + */ + irq_lock_sparse(); + + /* Arch-specific enabling code. */ + ret = __cpu_up(cpu, idle); + irq_unlock_sparse(); + if (ret) + return ret; + return bringup_wait_for_ap(cpu); +} + +static int finish_cpu(unsigned int cpu) +{ + struct task_struct *idle = idle_thread_get(cpu); + struct mm_struct *mm = idle->active_mm; + + /* + * idle_task_exit() will have switched to &init_mm, now + * clean up any remaining active_mm state. + */ + if (mm != &init_mm) + idle->active_mm = &init_mm; + mmdrop(mm); + return 0; +} + +/* + * Hotplug state machine related functions + */ + +static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st) +{ + for (st->state--; st->state > st->target; st->state--) + cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL); +} + +static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st) +{ + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) + return true; + /* + * When CPU hotplug is disabled, then taking the CPU down is not + * possible because takedown_cpu() and the architecture and + * subsystem specific mechanisms are not available. So the CPU + * which would be completely unplugged again needs to stay around + * in the current state. + */ + return st->state <= CPUHP_BRINGUP_CPU; +} + +static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, + enum cpuhp_state target) +{ + enum cpuhp_state prev_state = st->state; + int ret = 0; + + while (st->state < target) { + st->state++; + ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL); + if (ret) { + if (can_rollback_cpu(st)) { + st->target = prev_state; + undo_cpu_up(cpu, st); + } + break; + } + } + return ret; +} + +/* + * The cpu hotplug threads manage the bringup and teardown of the cpus + */ +static void cpuhp_create(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + + init_completion(&st->done_up); + init_completion(&st->done_down); +} + +static int cpuhp_should_run(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + + return st->should_run; +} + +/* + * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke + * callbacks when a state gets [un]installed at runtime. + * + * Each invocation of this function by the smpboot thread does a single AP + * state callback. + * + * It has 3 modes of operation: + * - single: runs st->cb_state + * - up: runs ++st->state, while st->state < st->target + * - down: runs st->state--, while st->state > st->target + * + * When complete or on error, should_run is cleared and the completion is fired. + */ +static void cpuhp_thread_fun(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + bool bringup = st->bringup; + enum cpuhp_state state; + + if (WARN_ON_ONCE(!st->should_run)) + return; + + /* + * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures + * that if we see ->should_run we also see the rest of the state. + */ + smp_mb(); + + cpuhp_lock_acquire(bringup); + + if (st->single) { + state = st->cb_state; + st->should_run = false; + } else { + if (bringup) { + st->state++; + state = st->state; + st->should_run = (st->state < st->target); + WARN_ON_ONCE(st->state > st->target); + } else { + state = st->state; + st->state--; + st->should_run = (st->state > st->target); + WARN_ON_ONCE(st->state < st->target); + } + } + + WARN_ON_ONCE(!cpuhp_is_ap_state(state)); + + if (cpuhp_is_atomic_state(state)) { + local_irq_disable(); + st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last); + local_irq_enable(); + + /* + * STARTING/DYING must not fail! + */ + WARN_ON_ONCE(st->result); + } else { + st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last); + } + + if (st->result) { + /* + * If we fail on a rollback, we're up a creek without no + * paddle, no way forward, no way back. We loose, thanks for + * playing. + */ + WARN_ON_ONCE(st->rollback); + st->should_run = false; + } + + cpuhp_lock_release(bringup); + + if (!st->should_run) + complete_ap_thread(st, bringup); +} + +/* Invoke a single callback on a remote cpu */ +static int +cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup, + struct hlist_node *node) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int ret; + + if (!cpu_online(cpu)) + return 0; + + cpuhp_lock_acquire(false); + cpuhp_lock_release(false); + + cpuhp_lock_acquire(true); + cpuhp_lock_release(true); + + /* + * If we are up and running, use the hotplug thread. For early calls + * we invoke the thread function directly. + */ + if (!st->thread) + return cpuhp_invoke_callback(cpu, state, bringup, node, NULL); + + st->rollback = false; + st->last = NULL; + + st->node = node; + st->bringup = bringup; + st->cb_state = state; + st->single = true; + + __cpuhp_kick_ap(st); + + /* + * If we failed and did a partial, do a rollback. + */ + if ((ret = st->result) && st->last) { + st->rollback = true; + st->bringup = !bringup; + + __cpuhp_kick_ap(st); + } + + /* + * Clean up the leftovers so the next hotplug operation wont use stale + * data. + */ + st->node = st->last = NULL; + return ret; +} + +static int cpuhp_kick_ap_work(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + enum cpuhp_state prev_state = st->state; + int ret; + + cpuhp_lock_acquire(false); + cpuhp_lock_release(false); + + cpuhp_lock_acquire(true); + cpuhp_lock_release(true); + + trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work); + ret = cpuhp_kick_ap(st, st->target); + trace_cpuhp_exit(cpu, st->state, prev_state, ret); + + return ret; +} + +static struct smp_hotplug_thread cpuhp_threads = { + .store = &cpuhp_state.thread, + .create = &cpuhp_create, + .thread_should_run = cpuhp_should_run, + .thread_fn = cpuhp_thread_fun, + .thread_comm = "cpuhp/%u", + .selfparking = true, +}; + +void __init cpuhp_threads_init(void) +{ + BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads)); + kthread_unpark(this_cpu_read(cpuhp_state.thread)); +} + +/* + * + * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock + * protected region. + * + * The operation is still serialized against concurrent CPU hotplug via + * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_ + * serialized against other hotplug related activity like adding or + * removing of state callbacks and state instances, which invoke either the + * startup or the teardown callback of the affected state. + * + * This is required for subsystems which are unfixable vs. CPU hotplug and + * evade lock inversion problems by scheduling work which has to be + * completed _before_ cpu_up()/_cpu_down() returns. + * + * Don't even think about adding anything to this for any new code or even + * drivers. It's only purpose is to keep existing lock order trainwrecks + * working. + * + * For cpu_down() there might be valid reasons to finish cleanups which are + * not required to be done under cpu_hotplug_lock, but that's a different + * story and would be not invoked via this. + */ +static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen) +{ + /* + * cpusets delegate hotplug operations to a worker to "solve" the + * lock order problems. Wait for the worker, but only if tasks are + * _not_ frozen (suspend, hibernate) as that would wait forever. + * + * The wait is required because otherwise the hotplug operation + * returns with inconsistent state, which could even be observed in + * user space when a new CPU is brought up. The CPU plug uevent + * would be delivered and user space reacting on it would fail to + * move tasks to the newly plugged CPU up to the point where the + * work has finished because up to that point the newly plugged CPU + * is not assignable in cpusets/cgroups. On unplug that's not + * necessarily a visible issue, but it is still inconsistent state, + * which is the real problem which needs to be "fixed". This can't + * prevent the transient state between scheduling the work and + * returning from waiting for it. + */ + if (!tasks_frozen) + cpuset_wait_for_hotplug(); +} + +#ifdef CONFIG_HOTPLUG_CPU +#ifndef arch_clear_mm_cpumask_cpu +#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm)) +#endif + +/** + * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU + * @cpu: a CPU id + * + * This function walks all processes, finds a valid mm struct for each one and + * then clears a corresponding bit in mm's cpumask. While this all sounds + * trivial, there are various non-obvious corner cases, which this function + * tries to solve in a safe manner. + * + * Also note that the function uses a somewhat relaxed locking scheme, so it may + * be called only for an already offlined CPU. + */ +void clear_tasks_mm_cpumask(int cpu) +{ + struct task_struct *p; + + /* + * This function is called after the cpu is taken down and marked + * offline, so its not like new tasks will ever get this cpu set in + * their mm mask. -- Peter Zijlstra + * Thus, we may use rcu_read_lock() here, instead of grabbing + * full-fledged tasklist_lock. + */ + WARN_ON(cpu_online(cpu)); + rcu_read_lock(); + for_each_process(p) { + struct task_struct *t; + + /* + * Main thread might exit, but other threads may still have + * a valid mm. Find one. + */ + t = find_lock_task_mm(p); + if (!t) + continue; + arch_clear_mm_cpumask_cpu(cpu, t->mm); + task_unlock(t); + } + rcu_read_unlock(); +} + +/* Take this CPU down. */ +static int take_cpu_down(void *_param) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE); + int err, cpu = smp_processor_id(); + int ret; + + /* Ensure this CPU doesn't handle any more interrupts. */ + err = __cpu_disable(); + if (err < 0) + return err; + + /* + * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not + * do this step again. + */ + WARN_ON(st->state != CPUHP_TEARDOWN_CPU); + st->state--; + /* Invoke the former CPU_DYING callbacks */ + for (; st->state > target; st->state--) { + ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL); + /* + * DYING must not fail! + */ + WARN_ON_ONCE(ret); + } + + /* Give up timekeeping duties */ + tick_handover_do_timer(); + /* Park the stopper thread */ + stop_machine_park(cpu); + return 0; +} + +static int takedown_cpu(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int err; + + /* Park the smpboot threads */ + kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread); + + /* + * Prevent irq alloc/free while the dying cpu reorganizes the + * interrupt affinities. + */ + irq_lock_sparse(); + + /* + * So now all preempt/rcu users must observe !cpu_active(). + */ + err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu)); + if (err) { + /* CPU refused to die */ + irq_unlock_sparse(); + /* Unpark the hotplug thread so we can rollback there */ + kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread); + return err; + } + BUG_ON(cpu_online(cpu)); + + /* + * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed + * all runnable tasks from the CPU, there's only the idle task left now + * that the migration thread is done doing the stop_machine thing. + * + * Wait for the stop thread to go away. + */ + wait_for_ap_thread(st, false); + BUG_ON(st->state != CPUHP_AP_IDLE_DEAD); + + /* Interrupts are moved away from the dying cpu, reenable alloc/free */ + irq_unlock_sparse(); + + hotplug_cpu__broadcast_tick_pull(cpu); + /* This actually kills the CPU. */ + __cpu_die(cpu); + + tick_cleanup_dead_cpu(cpu); + rcutree_migrate_callbacks(cpu); + return 0; +} + +static void cpuhp_complete_idle_dead(void *arg) +{ + struct cpuhp_cpu_state *st = arg; + + complete_ap_thread(st, false); +} + +void cpuhp_report_idle_dead(void) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + + BUG_ON(st->state != CPUHP_AP_OFFLINE); + rcu_report_dead(smp_processor_id()); + st->state = CPUHP_AP_IDLE_DEAD; + /* + * We cannot call complete after rcu_report_dead() so we delegate it + * to an online cpu. + */ + smp_call_function_single(cpumask_first(cpu_online_mask), + cpuhp_complete_idle_dead, st, 0); +} + +static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st) +{ + for (st->state++; st->state < st->target; st->state++) + cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL); +} + +static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, + enum cpuhp_state target) +{ + enum cpuhp_state prev_state = st->state; + int ret = 0; + + for (; st->state > target; st->state--) { + ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL); + if (ret) { + st->target = prev_state; + if (st->state < prev_state) + undo_cpu_down(cpu, st); + break; + } + } + return ret; +} + +/* Requires cpu_add_remove_lock to be held */ +static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, + enum cpuhp_state target) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int prev_state, ret = 0; + + if (num_online_cpus() == 1) + return -EBUSY; + + if (!cpu_present(cpu)) + return -EINVAL; + + cpus_write_lock(); + + cpuhp_tasks_frozen = tasks_frozen; + + prev_state = cpuhp_set_state(st, target); + /* + * If the current CPU state is in the range of the AP hotplug thread, + * then we need to kick the thread. + */ + if (st->state > CPUHP_TEARDOWN_CPU) { + st->target = max((int)target, CPUHP_TEARDOWN_CPU); + ret = cpuhp_kick_ap_work(cpu); + /* + * The AP side has done the error rollback already. Just + * return the error code.. + */ + if (ret) + goto out; + + /* + * We might have stopped still in the range of the AP hotplug + * thread. Nothing to do anymore. + */ + if (st->state > CPUHP_TEARDOWN_CPU) + goto out; + + st->target = target; + } + /* + * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need + * to do the further cleanups. + */ + ret = cpuhp_down_callbacks(cpu, st, target); + if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) { + cpuhp_reset_state(st, prev_state); + __cpuhp_kick_ap(st); + } + +out: + cpus_write_unlock(); + /* + * Do post unplug cleanup. This is still protected against + * concurrent CPU hotplug via cpu_add_remove_lock. + */ + lockup_detector_cleanup(); + arch_smt_update(); + cpu_up_down_serialize_trainwrecks(tasks_frozen); + return ret; +} + +static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) +{ + if (cpu_hotplug_disabled) + return -EBUSY; + return _cpu_down(cpu, 0, target); +} + +static int do_cpu_down(unsigned int cpu, enum cpuhp_state target) +{ + int err; + + cpu_maps_update_begin(); + err = cpu_down_maps_locked(cpu, target); + cpu_maps_update_done(); + return err; +} + +int cpu_down(unsigned int cpu) +{ + return do_cpu_down(cpu, CPUHP_OFFLINE); +} +EXPORT_SYMBOL(cpu_down); + +#else +#define takedown_cpu NULL +#endif /*CONFIG_HOTPLUG_CPU*/ + +/** + * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU + * @cpu: cpu that just started + * + * It must be called by the arch code on the new cpu, before the new cpu + * enables interrupts and before the "boot" cpu returns from __cpu_up(). + */ +void notify_cpu_starting(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE); + int ret; + + rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */ + st->booted_once = true; + while (st->state < target) { + st->state++; + ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL); + /* + * STARTING must not fail! + */ + WARN_ON_ONCE(ret); + } +} + +/* + * Called from the idle task. Wake up the controlling task which brings the + * hotplug thread of the upcoming CPU up and then delegates the rest of the + * online bringup to the hotplug thread. + */ +void cpuhp_online_idle(enum cpuhp_state state) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + + /* Happens for the boot cpu */ + if (state != CPUHP_AP_ONLINE_IDLE) + return; + + /* + * Unpart the stopper thread before we start the idle loop (and start + * scheduling); this ensures the stopper task is always available. + */ + stop_machine_unpark(smp_processor_id()); + + st->state = CPUHP_AP_ONLINE_IDLE; + complete_ap_thread(st, true); +} + +/* Requires cpu_add_remove_lock to be held */ +static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + struct task_struct *idle; + int ret = 0; + + cpus_write_lock(); + + if (!cpu_present(cpu)) { + ret = -EINVAL; + goto out; + } + + /* + * The caller of do_cpu_up might have raced with another + * caller. Ignore it for now. + */ + if (st->state >= target) + goto out; + + if (st->state == CPUHP_OFFLINE) { + /* Let it fail before we try to bring the cpu up */ + idle = idle_thread_get(cpu); + if (IS_ERR(idle)) { + ret = PTR_ERR(idle); + goto out; + } + } + + cpuhp_tasks_frozen = tasks_frozen; + + cpuhp_set_state(st, target); + /* + * If the current CPU state is in the range of the AP hotplug thread, + * then we need to kick the thread once more. + */ + if (st->state > CPUHP_BRINGUP_CPU) { + ret = cpuhp_kick_ap_work(cpu); + /* + * The AP side has done the error rollback already. Just + * return the error code.. + */ + if (ret) + goto out; + } + + /* + * Try to reach the target state. We max out on the BP at + * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is + * responsible for bringing it up to the target state. + */ + target = min((int)target, CPUHP_BRINGUP_CPU); + ret = cpuhp_up_callbacks(cpu, st, target); +out: + cpus_write_unlock(); + arch_smt_update(); + cpu_up_down_serialize_trainwrecks(tasks_frozen); + return ret; +} + +static int do_cpu_up(unsigned int cpu, enum cpuhp_state target) +{ + int err = 0; + + if (!cpu_possible(cpu)) { + pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n", + cpu); +#if defined(CONFIG_IA64) + pr_err("please check additional_cpus= boot parameter\n"); +#endif + return -EINVAL; + } + + err = try_online_node(cpu_to_node(cpu)); + if (err) + return err; + + cpu_maps_update_begin(); + + if (cpu_hotplug_disabled) { + err = -EBUSY; + goto out; + } + if (!cpu_smt_allowed(cpu)) { + err = -EPERM; + goto out; + } + + err = _cpu_up(cpu, 0, target); +out: + cpu_maps_update_done(); + return err; +} + +int cpu_up(unsigned int cpu) +{ + return do_cpu_up(cpu, CPUHP_ONLINE); +} +EXPORT_SYMBOL_GPL(cpu_up); + +#ifdef CONFIG_PM_SLEEP_SMP +static cpumask_var_t frozen_cpus; + +int freeze_secondary_cpus(int primary) +{ + int cpu, error = 0; + + cpu_maps_update_begin(); + if (!cpu_online(primary)) + primary = cpumask_first(cpu_online_mask); + /* + * We take down all of the non-boot CPUs in one shot to avoid races + * with the userspace trying to use the CPU hotplug at the same time + */ + cpumask_clear(frozen_cpus); + + pr_info("Disabling non-boot CPUs ...\n"); + for_each_online_cpu(cpu) { + if (cpu == primary) + continue; + trace_suspend_resume(TPS("CPU_OFF"), cpu, true); + error = _cpu_down(cpu, 1, CPUHP_OFFLINE); + trace_suspend_resume(TPS("CPU_OFF"), cpu, false); + if (!error) + cpumask_set_cpu(cpu, frozen_cpus); + else { + pr_err("Error taking CPU%d down: %d\n", cpu, error); + break; + } + } + + if (!error) + BUG_ON(num_online_cpus() > 1); + else + pr_err("Non-boot CPUs are not disabled\n"); + + /* + * Make sure the CPUs won't be enabled by someone else. We need to do + * this even in case of failure as all disable_nonboot_cpus() users are + * supposed to do enable_nonboot_cpus() on the failure path. + */ + cpu_hotplug_disabled++; + + cpu_maps_update_done(); + return error; +} + +void __weak arch_enable_nonboot_cpus_begin(void) +{ +} + +void __weak arch_enable_nonboot_cpus_end(void) +{ +} + +void enable_nonboot_cpus(void) +{ + int cpu, error; + + /* Allow everyone to use the CPU hotplug again */ + cpu_maps_update_begin(); + __cpu_hotplug_enable(); + if (cpumask_empty(frozen_cpus)) + goto out; + + pr_info("Enabling non-boot CPUs ...\n"); + + arch_enable_nonboot_cpus_begin(); + + for_each_cpu(cpu, frozen_cpus) { + trace_suspend_resume(TPS("CPU_ON"), cpu, true); + error = _cpu_up(cpu, 1, CPUHP_ONLINE); + trace_suspend_resume(TPS("CPU_ON"), cpu, false); + if (!error) { + pr_info("CPU%d is up\n", cpu); + continue; + } + pr_warn("Error taking CPU%d up: %d\n", cpu, error); + } + + arch_enable_nonboot_cpus_end(); + + cpumask_clear(frozen_cpus); +out: + cpu_maps_update_done(); +} + +static int __init alloc_frozen_cpus(void) +{ + if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO)) + return -ENOMEM; + return 0; +} +core_initcall(alloc_frozen_cpus); + +/* + * When callbacks for CPU hotplug notifications are being executed, we must + * ensure that the state of the system with respect to the tasks being frozen + * or not, as reported by the notification, remains unchanged *throughout the + * duration* of the execution of the callbacks. + * Hence we need to prevent the freezer from racing with regular CPU hotplug. + * + * This synchronization is implemented by mutually excluding regular CPU + * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/ + * Hibernate notifications. + */ +static int +cpu_hotplug_pm_callback(struct notifier_block *nb, + unsigned long action, void *ptr) +{ + switch (action) { + + case PM_SUSPEND_PREPARE: + case PM_HIBERNATION_PREPARE: + cpu_hotplug_disable(); + break; + + case PM_POST_SUSPEND: + case PM_POST_HIBERNATION: + cpu_hotplug_enable(); + break; + + default: + return NOTIFY_DONE; + } + + return NOTIFY_OK; +} + + +static int __init cpu_hotplug_pm_sync_init(void) +{ + /* + * cpu_hotplug_pm_callback has higher priority than x86 + * bsp_pm_callback which depends on cpu_hotplug_pm_callback + * to disable cpu hotplug to avoid cpu hotplug race. + */ + pm_notifier(cpu_hotplug_pm_callback, 0); + return 0; +} +core_initcall(cpu_hotplug_pm_sync_init); + +#endif /* CONFIG_PM_SLEEP_SMP */ + +int __boot_cpu_id; + +#endif /* CONFIG_SMP */ + +/* Boot processor state steps */ +static struct cpuhp_step cpuhp_hp_states[] = { + [CPUHP_OFFLINE] = { + .name = "offline", + .startup.single = NULL, + .teardown.single = NULL, + }, +#ifdef CONFIG_SMP + [CPUHP_CREATE_THREADS]= { + .name = "threads:prepare", + .startup.single = smpboot_create_threads, + .teardown.single = NULL, + .cant_stop = true, + }, + [CPUHP_PERF_PREPARE] = { + .name = "perf:prepare", + .startup.single = perf_event_init_cpu, + .teardown.single = perf_event_exit_cpu, + }, + [CPUHP_RANDOM_PREPARE] = { + .name = "random:prepare", + .startup.single = random_prepare_cpu, + .teardown.single = NULL, + }, + [CPUHP_WORKQUEUE_PREP] = { + .name = "workqueue:prepare", + .startup.single = workqueue_prepare_cpu, + .teardown.single = NULL, + }, + [CPUHP_HRTIMERS_PREPARE] = { + .name = "hrtimers:prepare", + .startup.single = hrtimers_prepare_cpu, + .teardown.single = hrtimers_dead_cpu, + }, + [CPUHP_SMPCFD_PREPARE] = { + .name = "smpcfd:prepare", + .startup.single = smpcfd_prepare_cpu, + .teardown.single = smpcfd_dead_cpu, + }, + [CPUHP_RELAY_PREPARE] = { + .name = "relay:prepare", + .startup.single = relay_prepare_cpu, + .teardown.single = NULL, + }, + [CPUHP_SLAB_PREPARE] = { + .name = "slab:prepare", + .startup.single = slab_prepare_cpu, + .teardown.single = slab_dead_cpu, + }, + [CPUHP_RCUTREE_PREP] = { + .name = "RCU/tree:prepare", + .startup.single = rcutree_prepare_cpu, + .teardown.single = rcutree_dead_cpu, + }, + /* + * On the tear-down path, timers_dead_cpu() must be invoked + * before blk_mq_queue_reinit_notify() from notify_dead(), + * otherwise a RCU stall occurs. + */ + [CPUHP_TIMERS_PREPARE] = { + .name = "timers:prepare", + .startup.single = timers_prepare_cpu, + .teardown.single = timers_dead_cpu, + }, + /* Kicks the plugged cpu into life */ + [CPUHP_BRINGUP_CPU] = { + .name = "cpu:bringup", + .startup.single = bringup_cpu, + .teardown.single = finish_cpu, + .cant_stop = true, + }, + /* Final state before CPU kills itself */ + [CPUHP_AP_IDLE_DEAD] = { + .name = "idle:dead", + }, + /* + * Last state before CPU enters the idle loop to die. Transient state + * for synchronization. + */ + [CPUHP_AP_OFFLINE] = { + .name = "ap:offline", + .cant_stop = true, + }, + /* First state is scheduler control. Interrupts are disabled */ + [CPUHP_AP_SCHED_STARTING] = { + .name = "sched:starting", + .startup.single = sched_cpu_starting, + .teardown.single = sched_cpu_dying, + }, + [CPUHP_AP_RCUTREE_DYING] = { + .name = "RCU/tree:dying", + .startup.single = NULL, + .teardown.single = rcutree_dying_cpu, + }, + [CPUHP_AP_SMPCFD_DYING] = { + .name = "smpcfd:dying", + .startup.single = NULL, + .teardown.single = smpcfd_dying_cpu, + }, + /* Entry state on starting. Interrupts enabled from here on. Transient + * state for synchronsization */ + [CPUHP_AP_ONLINE] = { + .name = "ap:online", + }, + /* + * Handled on controll processor until the plugged processor manages + * this itself. + */ + [CPUHP_TEARDOWN_CPU] = { + .name = "cpu:teardown", + .startup.single = NULL, + .teardown.single = takedown_cpu, + .cant_stop = true, + }, + /* Handle smpboot threads park/unpark */ + [CPUHP_AP_SMPBOOT_THREADS] = { + .name = "smpboot/threads:online", + .startup.single = smpboot_unpark_threads, + .teardown.single = smpboot_park_threads, + }, + [CPUHP_AP_IRQ_AFFINITY_ONLINE] = { + .name = "irq/affinity:online", + .startup.single = irq_affinity_online_cpu, + .teardown.single = NULL, + }, + [CPUHP_AP_PERF_ONLINE] = { + .name = "perf:online", + .startup.single = perf_event_init_cpu, + .teardown.single = perf_event_exit_cpu, + }, + [CPUHP_AP_WATCHDOG_ONLINE] = { + .name = "lockup_detector:online", + .startup.single = lockup_detector_online_cpu, + .teardown.single = lockup_detector_offline_cpu, + }, + [CPUHP_AP_WORKQUEUE_ONLINE] = { + .name = "workqueue:online", + .startup.single = workqueue_online_cpu, + .teardown.single = workqueue_offline_cpu, + }, + [CPUHP_AP_RANDOM_ONLINE] = { + .name = "random:online", + .startup.single = random_online_cpu, + .teardown.single = NULL, + }, + [CPUHP_AP_RCUTREE_ONLINE] = { + .name = "RCU/tree:online", + .startup.single = rcutree_online_cpu, + .teardown.single = rcutree_offline_cpu, + }, +#endif + /* + * The dynamically registered state space is here + */ + +#ifdef CONFIG_SMP + /* Last state is scheduler control setting the cpu active */ + [CPUHP_AP_ACTIVE] = { + .name = "sched:active", + .startup.single = sched_cpu_activate, + .teardown.single = sched_cpu_deactivate, + }, +#endif + + /* CPU is fully up and running. */ + [CPUHP_ONLINE] = { + .name = "online", + .startup.single = NULL, + .teardown.single = NULL, + }, +}; + +/* Sanity check for callbacks */ +static int cpuhp_cb_check(enum cpuhp_state state) +{ + if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE) + return -EINVAL; + return 0; +} + +/* + * Returns a free for dynamic slot assignment of the Online state. The states + * are protected by the cpuhp_slot_states mutex and an empty slot is identified + * by having no name assigned. + */ +static int cpuhp_reserve_state(enum cpuhp_state state) +{ + enum cpuhp_state i, end; + struct cpuhp_step *step; + + switch (state) { + case CPUHP_AP_ONLINE_DYN: + step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN; + end = CPUHP_AP_ONLINE_DYN_END; + break; + case CPUHP_BP_PREPARE_DYN: + step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN; + end = CPUHP_BP_PREPARE_DYN_END; + break; + default: + return -EINVAL; + } + + for (i = state; i <= end; i++, step++) { + if (!step->name) + return i; + } + WARN(1, "No more dynamic states available for CPU hotplug\n"); + return -ENOSPC; +} + +static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name, + int (*startup)(unsigned int cpu), + int (*teardown)(unsigned int cpu), + bool multi_instance) +{ + /* (Un)Install the callbacks for further cpu hotplug operations */ + struct cpuhp_step *sp; + int ret = 0; + + /* + * If name is NULL, then the state gets removed. + * + * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on + * the first allocation from these dynamic ranges, so the removal + * would trigger a new allocation and clear the wrong (already + * empty) state, leaving the callbacks of the to be cleared state + * dangling, which causes wreckage on the next hotplug operation. + */ + if (name && (state == CPUHP_AP_ONLINE_DYN || + state == CPUHP_BP_PREPARE_DYN)) { + ret = cpuhp_reserve_state(state); + if (ret < 0) + return ret; + state = ret; + } + sp = cpuhp_get_step(state); + if (name && sp->name) + return -EBUSY; + + sp->startup.single = startup; + sp->teardown.single = teardown; + sp->name = name; + sp->multi_instance = multi_instance; + INIT_HLIST_HEAD(&sp->list); + return ret; +} + +static void *cpuhp_get_teardown_cb(enum cpuhp_state state) +{ + return cpuhp_get_step(state)->teardown.single; +} + +/* + * Call the startup/teardown function for a step either on the AP or + * on the current CPU. + */ +static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup, + struct hlist_node *node) +{ + struct cpuhp_step *sp = cpuhp_get_step(state); + int ret; + + /* + * If there's nothing to do, we done. + * Relies on the union for multi_instance. + */ + if ((bringup && !sp->startup.single) || + (!bringup && !sp->teardown.single)) + return 0; + /* + * The non AP bound callbacks can fail on bringup. On teardown + * e.g. module removal we crash for now. + */ +#ifdef CONFIG_SMP + if (cpuhp_is_ap_state(state)) + ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node); + else + ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); +#else + ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL); +#endif + BUG_ON(ret && !bringup); + return ret; +} + +/* + * Called from __cpuhp_setup_state on a recoverable failure. + * + * Note: The teardown callbacks for rollback are not allowed to fail! + */ +static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state, + struct hlist_node *node) +{ + int cpu; + + /* Roll back the already executed steps on the other cpus */ + for_each_present_cpu(cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int cpustate = st->state; + + if (cpu >= failedcpu) + break; + + /* Did we invoke the startup call on that cpu ? */ + if (cpustate >= state) + cpuhp_issue_call(cpu, state, false, node); + } +} + +int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state, + struct hlist_node *node, + bool invoke) +{ + struct cpuhp_step *sp; + int cpu; + int ret; + + lockdep_assert_cpus_held(); + + sp = cpuhp_get_step(state); + if (sp->multi_instance == false) + return -EINVAL; + + mutex_lock(&cpuhp_state_mutex); + + if (!invoke || !sp->startup.multi) + goto add_node; + + /* + * Try to call the startup callback for each present cpu + * depending on the hotplug state of the cpu. + */ + for_each_present_cpu(cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int cpustate = st->state; + + if (cpustate < state) + continue; + + ret = cpuhp_issue_call(cpu, state, true, node); + if (ret) { + if (sp->teardown.multi) + cpuhp_rollback_install(cpu, state, node); + goto unlock; + } + } +add_node: + ret = 0; + hlist_add_head(node, &sp->list); +unlock: + mutex_unlock(&cpuhp_state_mutex); + return ret; +} + +int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node, + bool invoke) +{ + int ret; + + cpus_read_lock(); + ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke); + cpus_read_unlock(); + return ret; +} +EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance); + +/** + * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state + * @state: The state to setup + * @invoke: If true, the startup function is invoked for cpus where + * cpu state >= @state + * @startup: startup callback function + * @teardown: teardown callback function + * @multi_instance: State is set up for multiple instances which get + * added afterwards. + * + * The caller needs to hold cpus read locked while calling this function. + * Returns: + * On success: + * Positive state number if @state is CPUHP_AP_ONLINE_DYN + * 0 for all other states + * On failure: proper (negative) error code + */ +int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state, + const char *name, bool invoke, + int (*startup)(unsigned int cpu), + int (*teardown)(unsigned int cpu), + bool multi_instance) +{ + int cpu, ret = 0; + bool dynstate; + + lockdep_assert_cpus_held(); + + if (cpuhp_cb_check(state) || !name) + return -EINVAL; + + mutex_lock(&cpuhp_state_mutex); + + ret = cpuhp_store_callbacks(state, name, startup, teardown, + multi_instance); + + dynstate = state == CPUHP_AP_ONLINE_DYN; + if (ret > 0 && dynstate) { + state = ret; + ret = 0; + } + + if (ret || !invoke || !startup) + goto out; + + /* + * Try to call the startup callback for each present cpu + * depending on the hotplug state of the cpu. + */ + for_each_present_cpu(cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int cpustate = st->state; + + if (cpustate < state) + continue; + + ret = cpuhp_issue_call(cpu, state, true, NULL); + if (ret) { + if (teardown) + cpuhp_rollback_install(cpu, state, NULL); + cpuhp_store_callbacks(state, NULL, NULL, NULL, false); + goto out; + } + } +out: + mutex_unlock(&cpuhp_state_mutex); + /* + * If the requested state is CPUHP_AP_ONLINE_DYN, return the + * dynamically allocated state in case of success. + */ + if (!ret && dynstate) + return state; + return ret; +} +EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked); + +int __cpuhp_setup_state(enum cpuhp_state state, + const char *name, bool invoke, + int (*startup)(unsigned int cpu), + int (*teardown)(unsigned int cpu), + bool multi_instance) +{ + int ret; + + cpus_read_lock(); + ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup, + teardown, multi_instance); + cpus_read_unlock(); + return ret; +} +EXPORT_SYMBOL(__cpuhp_setup_state); + +int __cpuhp_state_remove_instance(enum cpuhp_state state, + struct hlist_node *node, bool invoke) +{ + struct cpuhp_step *sp = cpuhp_get_step(state); + int cpu; + + BUG_ON(cpuhp_cb_check(state)); + + if (!sp->multi_instance) + return -EINVAL; + + cpus_read_lock(); + mutex_lock(&cpuhp_state_mutex); + + if (!invoke || !cpuhp_get_teardown_cb(state)) + goto remove; + /* + * Call the teardown callback for each present cpu depending + * on the hotplug state of the cpu. This function is not + * allowed to fail currently! + */ + for_each_present_cpu(cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int cpustate = st->state; + + if (cpustate >= state) + cpuhp_issue_call(cpu, state, false, node); + } + +remove: + hlist_del(node); + mutex_unlock(&cpuhp_state_mutex); + cpus_read_unlock(); + + return 0; +} +EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance); + +/** + * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state + * @state: The state to remove + * @invoke: If true, the teardown function is invoked for cpus where + * cpu state >= @state + * + * The caller needs to hold cpus read locked while calling this function. + * The teardown callback is currently not allowed to fail. Think + * about module removal! + */ +void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke) +{ + struct cpuhp_step *sp = cpuhp_get_step(state); + int cpu; + + BUG_ON(cpuhp_cb_check(state)); + + lockdep_assert_cpus_held(); + + mutex_lock(&cpuhp_state_mutex); + if (sp->multi_instance) { + WARN(!hlist_empty(&sp->list), + "Error: Removing state %d which has instances left.\n", + state); + goto remove; + } + + if (!invoke || !cpuhp_get_teardown_cb(state)) + goto remove; + + /* + * Call the teardown callback for each present cpu depending + * on the hotplug state of the cpu. This function is not + * allowed to fail currently! + */ + for_each_present_cpu(cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + int cpustate = st->state; + + if (cpustate >= state) + cpuhp_issue_call(cpu, state, false, NULL); + } +remove: + cpuhp_store_callbacks(state, NULL, NULL, NULL, false); + mutex_unlock(&cpuhp_state_mutex); +} +EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked); + +void __cpuhp_remove_state(enum cpuhp_state state, bool invoke) +{ + cpus_read_lock(); + __cpuhp_remove_state_cpuslocked(state, invoke); + cpus_read_unlock(); +} +EXPORT_SYMBOL(__cpuhp_remove_state); + +#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU) +static ssize_t show_cpuhp_state(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id); + + return sprintf(buf, "%d\n", st->state); +} +static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL); + +static ssize_t write_cpuhp_target(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id); + struct cpuhp_step *sp; + int target, ret; + + ret = kstrtoint(buf, 10, &target); + if (ret) + return ret; + +#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL + if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE) + return -EINVAL; +#else + if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE) + return -EINVAL; +#endif + + ret = lock_device_hotplug_sysfs(); + if (ret) + return ret; + + mutex_lock(&cpuhp_state_mutex); + sp = cpuhp_get_step(target); + ret = !sp->name || sp->cant_stop ? -EINVAL : 0; + mutex_unlock(&cpuhp_state_mutex); + if (ret) + goto out; + + if (st->state < target) + ret = do_cpu_up(dev->id, target); + else + ret = do_cpu_down(dev->id, target); +out: + unlock_device_hotplug(); + return ret ? ret : count; +} + +static ssize_t show_cpuhp_target(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id); + + return sprintf(buf, "%d\n", st->target); +} +static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target); + + +static ssize_t write_cpuhp_fail(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id); + struct cpuhp_step *sp; + int fail, ret; + + ret = kstrtoint(buf, 10, &fail); + if (ret) + return ret; + + if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE) + return -EINVAL; + + /* + * Cannot fail STARTING/DYING callbacks. + */ + if (cpuhp_is_atomic_state(fail)) + return -EINVAL; + + /* + * Cannot fail anything that doesn't have callbacks. + */ + mutex_lock(&cpuhp_state_mutex); + sp = cpuhp_get_step(fail); + if (!sp->startup.single && !sp->teardown.single) + ret = -EINVAL; + mutex_unlock(&cpuhp_state_mutex); + if (ret) + return ret; + + st->fail = fail; + + return count; +} + +static ssize_t show_cpuhp_fail(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id); + + return sprintf(buf, "%d\n", st->fail); +} + +static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail); + +static struct attribute *cpuhp_cpu_attrs[] = { + &dev_attr_state.attr, + &dev_attr_target.attr, + &dev_attr_fail.attr, + NULL +}; + +static const struct attribute_group cpuhp_cpu_attr_group = { + .attrs = cpuhp_cpu_attrs, + .name = "hotplug", + NULL +}; + +static ssize_t show_cpuhp_states(struct device *dev, + struct device_attribute *attr, char *buf) +{ + ssize_t cur, res = 0; + int i; + + mutex_lock(&cpuhp_state_mutex); + for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) { + struct cpuhp_step *sp = cpuhp_get_step(i); + + if (sp->name) { + cur = sprintf(buf, "%3d: %s\n", i, sp->name); + buf += cur; + res += cur; + } + } + mutex_unlock(&cpuhp_state_mutex); + return res; +} +static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL); + +static struct attribute *cpuhp_cpu_root_attrs[] = { + &dev_attr_states.attr, + NULL +}; + +static const struct attribute_group cpuhp_cpu_root_attr_group = { + .attrs = cpuhp_cpu_root_attrs, + .name = "hotplug", + NULL +}; + +#ifdef CONFIG_HOTPLUG_SMT + +static const char *smt_states[] = { + [CPU_SMT_ENABLED] = "on", + [CPU_SMT_DISABLED] = "off", + [CPU_SMT_FORCE_DISABLED] = "forceoff", + [CPU_SMT_NOT_SUPPORTED] = "notsupported", +}; + +static ssize_t +show_smt_control(struct device *dev, struct device_attribute *attr, char *buf) +{ + return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]); +} + +static void cpuhp_offline_cpu_device(unsigned int cpu) +{ + struct device *dev = get_cpu_device(cpu); + + dev->offline = true; + /* Tell user space about the state change */ + kobject_uevent(&dev->kobj, KOBJ_OFFLINE); +} + +static void cpuhp_online_cpu_device(unsigned int cpu) +{ + struct device *dev = get_cpu_device(cpu); + + dev->offline = false; + /* Tell user space about the state change */ + kobject_uevent(&dev->kobj, KOBJ_ONLINE); +} + +int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) +{ + int cpu, ret = 0; + + cpu_maps_update_begin(); + for_each_online_cpu(cpu) { + if (topology_is_primary_thread(cpu)) + continue; + ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE); + if (ret) + break; + /* + * As this needs to hold the cpu maps lock it's impossible + * to call device_offline() because that ends up calling + * cpu_down() which takes cpu maps lock. cpu maps lock + * needs to be held as this might race against in kernel + * abusers of the hotplug machinery (thermal management). + * + * So nothing would update device:offline state. That would + * leave the sysfs entry stale and prevent onlining after + * smt control has been changed to 'off' again. This is + * called under the sysfs hotplug lock, so it is properly + * serialized against the regular offline usage. + */ + cpuhp_offline_cpu_device(cpu); + } + if (!ret) + cpu_smt_control = ctrlval; + cpu_maps_update_done(); + return ret; +} + +int cpuhp_smt_enable(void) +{ + int cpu, ret = 0; + + cpu_maps_update_begin(); + cpu_smt_control = CPU_SMT_ENABLED; + for_each_present_cpu(cpu) { + /* Skip online CPUs and CPUs on offline nodes */ + if (cpu_online(cpu) || !node_online(cpu_to_node(cpu))) + continue; + ret = _cpu_up(cpu, 0, CPUHP_ONLINE); + if (ret) + break; + /* See comment in cpuhp_smt_disable() */ + cpuhp_online_cpu_device(cpu); + } + cpu_maps_update_done(); + return ret; +} + +static ssize_t +store_smt_control(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + int ctrlval, ret; + + if (sysfs_streq(buf, "on")) + ctrlval = CPU_SMT_ENABLED; + else if (sysfs_streq(buf, "off")) + ctrlval = CPU_SMT_DISABLED; + else if (sysfs_streq(buf, "forceoff")) + ctrlval = CPU_SMT_FORCE_DISABLED; + else + return -EINVAL; + + if (cpu_smt_control == CPU_SMT_FORCE_DISABLED) + return -EPERM; + + if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED) + return -ENODEV; + + ret = lock_device_hotplug_sysfs(); + if (ret) + return ret; + + if (ctrlval != cpu_smt_control) { + switch (ctrlval) { + case CPU_SMT_ENABLED: + ret = cpuhp_smt_enable(); + break; + case CPU_SMT_DISABLED: + case CPU_SMT_FORCE_DISABLED: + ret = cpuhp_smt_disable(ctrlval); + break; + } + } + + unlock_device_hotplug(); + return ret ? ret : count; +} +static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control); + +static ssize_t +show_smt_active(struct device *dev, struct device_attribute *attr, char *buf) +{ + bool active = topology_max_smt_threads() > 1; + + return snprintf(buf, PAGE_SIZE - 2, "%d\n", active); +} +static DEVICE_ATTR(active, 0444, show_smt_active, NULL); + +static struct attribute *cpuhp_smt_attrs[] = { + &dev_attr_control.attr, + &dev_attr_active.attr, + NULL +}; + +static const struct attribute_group cpuhp_smt_attr_group = { + .attrs = cpuhp_smt_attrs, + .name = "smt", + NULL +}; + +static int __init cpu_smt_state_init(void) +{ + return sysfs_create_group(&cpu_subsys.dev_root->kobj, + &cpuhp_smt_attr_group); +} + +#else +static inline int cpu_smt_state_init(void) { return 0; } +#endif + +static int __init cpuhp_sysfs_init(void) +{ + int cpu, ret; + + ret = cpu_smt_state_init(); + if (ret) + return ret; + + ret = sysfs_create_group(&cpu_subsys.dev_root->kobj, + &cpuhp_cpu_root_attr_group); + if (ret) + return ret; + + for_each_possible_cpu(cpu) { + struct device *dev = get_cpu_device(cpu); + + if (!dev) + continue; + ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group); + if (ret) + return ret; + } + return 0; +} +device_initcall(cpuhp_sysfs_init); +#endif + +/* + * cpu_bit_bitmap[] is a special, "compressed" data structure that + * represents all NR_CPUS bits binary values of 1<<nr. + * + * It is used by cpumask_of() to get a constant address to a CPU + * mask value that has a single bit set only. + */ + +/* cpu_bit_bitmap[0] is empty - so we can back into it */ +#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x)) +#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1) +#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2) +#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4) + +const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = { + + MASK_DECLARE_8(0), MASK_DECLARE_8(8), + MASK_DECLARE_8(16), MASK_DECLARE_8(24), +#if BITS_PER_LONG > 32 + MASK_DECLARE_8(32), MASK_DECLARE_8(40), + MASK_DECLARE_8(48), MASK_DECLARE_8(56), +#endif +}; +EXPORT_SYMBOL_GPL(cpu_bit_bitmap); + +const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL; +EXPORT_SYMBOL(cpu_all_bits); + +#ifdef CONFIG_INIT_ALL_POSSIBLE +struct cpumask __cpu_possible_mask __read_mostly + = {CPU_BITS_ALL}; +#else +struct cpumask __cpu_possible_mask __read_mostly; +#endif +EXPORT_SYMBOL(__cpu_possible_mask); + +struct cpumask __cpu_online_mask __read_mostly; +EXPORT_SYMBOL(__cpu_online_mask); + +struct cpumask __cpu_present_mask __read_mostly; +EXPORT_SYMBOL(__cpu_present_mask); + +struct cpumask __cpu_active_mask __read_mostly; +EXPORT_SYMBOL(__cpu_active_mask); + +void init_cpu_present(const struct cpumask *src) +{ + cpumask_copy(&__cpu_present_mask, src); +} + +void init_cpu_possible(const struct cpumask *src) +{ + cpumask_copy(&__cpu_possible_mask, src); +} + +void init_cpu_online(const struct cpumask *src) +{ + cpumask_copy(&__cpu_online_mask, src); +} + +/* + * Activate the first processor. + */ +void __init boot_cpu_init(void) +{ + int cpu = smp_processor_id(); + + /* Mark the boot cpu "present", "online" etc for SMP and UP case */ + set_cpu_online(cpu, true); + set_cpu_active(cpu, true); + set_cpu_present(cpu, true); + set_cpu_possible(cpu, true); + +#ifdef CONFIG_SMP + __boot_cpu_id = cpu; +#endif +} + +/* + * Must be called _AFTER_ setting up the per_cpu areas + */ +void __init boot_cpu_hotplug_init(void) +{ +#ifdef CONFIG_SMP + this_cpu_write(cpuhp_state.booted_once, true); +#endif + this_cpu_write(cpuhp_state.state, CPUHP_ONLINE); +} + +/* + * These are used for a global "mitigations=" cmdline option for toggling + * optional CPU mitigations. + */ +enum cpu_mitigations { + CPU_MITIGATIONS_OFF, + CPU_MITIGATIONS_AUTO, + CPU_MITIGATIONS_AUTO_NOSMT, +}; + +static enum cpu_mitigations cpu_mitigations __ro_after_init = + CPU_MITIGATIONS_AUTO; + +static int __init mitigations_parse_cmdline(char *arg) +{ + if (!strcmp(arg, "off")) + cpu_mitigations = CPU_MITIGATIONS_OFF; + else if (!strcmp(arg, "auto")) + cpu_mitigations = CPU_MITIGATIONS_AUTO; + else if (!strcmp(arg, "auto,nosmt")) + cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT; + else + pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n", + arg); + + return 0; +} +early_param("mitigations", mitigations_parse_cmdline); + +/* mitigations=off */ +bool cpu_mitigations_off(void) +{ + return cpu_mitigations == CPU_MITIGATIONS_OFF; +} +EXPORT_SYMBOL_GPL(cpu_mitigations_off); + +/* mitigations=auto,nosmt */ +bool cpu_mitigations_auto_nosmt(void) +{ + return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT; +} +EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt); |