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Diffstat (limited to '')
| -rw-r--r-- | kernel/kthread.c | 1534 |
1 files changed, 1534 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c new file mode 100644 index 0000000000..1eea53050b --- /dev/null +++ b/kernel/kthread.c @@ -0,0 +1,1534 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Kernel thread helper functions. + * Copyright (C) 2004 IBM Corporation, Rusty Russell. + * Copyright (C) 2009 Red Hat, Inc. + * + * Creation is done via kthreadd, so that we get a clean environment + * even if we're invoked from userspace (think modprobe, hotplug cpu, + * etc.). + */ +#include <uapi/linux/sched/types.h> +#include <linux/mm.h> +#include <linux/mmu_context.h> +#include <linux/sched.h> +#include <linux/sched/mm.h> +#include <linux/sched/task.h> +#include <linux/kthread.h> +#include <linux/completion.h> +#include <linux/err.h> +#include <linux/cgroup.h> +#include <linux/cpuset.h> +#include <linux/unistd.h> +#include <linux/file.h> +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/slab.h> +#include <linux/freezer.h> +#include <linux/ptrace.h> +#include <linux/uaccess.h> +#include <linux/numa.h> +#include <linux/sched/isolation.h> +#include <trace/events/sched.h> + + +static DEFINE_SPINLOCK(kthread_create_lock); +static LIST_HEAD(kthread_create_list); +struct task_struct *kthreadd_task; + +struct kthread_create_info +{ + /* Information passed to kthread() from kthreadd. */ + char *full_name; + int (*threadfn)(void *data); + void *data; + int node; + + /* Result passed back to kthread_create() from kthreadd. */ + struct task_struct *result; + struct completion *done; + + struct list_head list; +}; + +struct kthread { + unsigned long flags; + unsigned int cpu; + int result; + int (*threadfn)(void *); + void *data; + struct completion parked; + struct completion exited; +#ifdef CONFIG_BLK_CGROUP + struct cgroup_subsys_state *blkcg_css; +#endif + /* To store the full name if task comm is truncated. */ + char *full_name; +}; + +enum KTHREAD_BITS { + KTHREAD_IS_PER_CPU = 0, + KTHREAD_SHOULD_STOP, + KTHREAD_SHOULD_PARK, +}; + +static inline struct kthread *to_kthread(struct task_struct *k) +{ + WARN_ON(!(k->flags & PF_KTHREAD)); + return k->worker_private; +} + +/* + * Variant of to_kthread() that doesn't assume @p is a kthread. + * + * Per construction; when: + * + * (p->flags & PF_KTHREAD) && p->worker_private + * + * the task is both a kthread and struct kthread is persistent. However + * PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and + * begin_new_exec()). + */ +static inline struct kthread *__to_kthread(struct task_struct *p) +{ + void *kthread = p->worker_private; + if (kthread && !(p->flags & PF_KTHREAD)) + kthread = NULL; + return kthread; +} + +void get_kthread_comm(char *buf, size_t buf_size, struct task_struct *tsk) +{ + struct kthread *kthread = to_kthread(tsk); + + if (!kthread || !kthread->full_name) { + __get_task_comm(buf, buf_size, tsk); + return; + } + + strscpy_pad(buf, kthread->full_name, buf_size); +} + +bool set_kthread_struct(struct task_struct *p) +{ + struct kthread *kthread; + + if (WARN_ON_ONCE(to_kthread(p))) + return false; + + kthread = kzalloc(sizeof(*kthread), GFP_KERNEL); + if (!kthread) + return false; + + init_completion(&kthread->exited); + init_completion(&kthread->parked); + p->vfork_done = &kthread->exited; + + p->worker_private = kthread; + return true; +} + +void free_kthread_struct(struct task_struct *k) +{ + struct kthread *kthread; + + /* + * Can be NULL if kmalloc() in set_kthread_struct() failed. + */ + kthread = to_kthread(k); + if (!kthread) + return; + +#ifdef CONFIG_BLK_CGROUP + WARN_ON_ONCE(kthread->blkcg_css); +#endif + k->worker_private = NULL; + kfree(kthread->full_name); + kfree(kthread); +} + +/** + * kthread_should_stop - should this kthread return now? + * + * When someone calls kthread_stop() on your kthread, it will be woken + * and this will return true. You should then return, and your return + * value will be passed through to kthread_stop(). + */ +bool kthread_should_stop(void) +{ + return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags); +} +EXPORT_SYMBOL(kthread_should_stop); + +static bool __kthread_should_park(struct task_struct *k) +{ + return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags); +} + +/** + * kthread_should_park - should this kthread park now? + * + * When someone calls kthread_park() on your kthread, it will be woken + * and this will return true. You should then do the necessary + * cleanup and call kthread_parkme() + * + * Similar to kthread_should_stop(), but this keeps the thread alive + * and in a park position. kthread_unpark() "restarts" the thread and + * calls the thread function again. + */ +bool kthread_should_park(void) +{ + return __kthread_should_park(current); +} +EXPORT_SYMBOL_GPL(kthread_should_park); + +bool kthread_should_stop_or_park(void) +{ + struct kthread *kthread = __to_kthread(current); + + if (!kthread) + return false; + + return kthread->flags & (BIT(KTHREAD_SHOULD_STOP) | BIT(KTHREAD_SHOULD_PARK)); +} + +/** + * kthread_freezable_should_stop - should this freezable kthread return now? + * @was_frozen: optional out parameter, indicates whether %current was frozen + * + * kthread_should_stop() for freezable kthreads, which will enter + * refrigerator if necessary. This function is safe from kthread_stop() / + * freezer deadlock and freezable kthreads should use this function instead + * of calling try_to_freeze() directly. + */ +bool kthread_freezable_should_stop(bool *was_frozen) +{ + bool frozen = false; + + might_sleep(); + + if (unlikely(freezing(current))) + frozen = __refrigerator(true); + + if (was_frozen) + *was_frozen = frozen; + + return kthread_should_stop(); +} +EXPORT_SYMBOL_GPL(kthread_freezable_should_stop); + +/** + * kthread_func - return the function specified on kthread creation + * @task: kthread task in question + * + * Returns NULL if the task is not a kthread. + */ +void *kthread_func(struct task_struct *task) +{ + struct kthread *kthread = __to_kthread(task); + if (kthread) + return kthread->threadfn; + return NULL; +} +EXPORT_SYMBOL_GPL(kthread_func); + +/** + * kthread_data - return data value specified on kthread creation + * @task: kthread task in question + * + * Return the data value specified when kthread @task was created. + * The caller is responsible for ensuring the validity of @task when + * calling this function. + */ +void *kthread_data(struct task_struct *task) +{ + return to_kthread(task)->data; +} +EXPORT_SYMBOL_GPL(kthread_data); + +/** + * kthread_probe_data - speculative version of kthread_data() + * @task: possible kthread task in question + * + * @task could be a kthread task. Return the data value specified when it + * was created if accessible. If @task isn't a kthread task or its data is + * inaccessible for any reason, %NULL is returned. This function requires + * that @task itself is safe to dereference. + */ +void *kthread_probe_data(struct task_struct *task) +{ + struct kthread *kthread = __to_kthread(task); + void *data = NULL; + + if (kthread) + copy_from_kernel_nofault(&data, &kthread->data, sizeof(data)); + return data; +} + +static void __kthread_parkme(struct kthread *self) +{ + for (;;) { + /* + * TASK_PARKED is a special state; we must serialize against + * possible pending wakeups to avoid store-store collisions on + * task->state. + * + * Such a collision might possibly result in the task state + * changin from TASK_PARKED and us failing the + * wait_task_inactive() in kthread_park(). + */ + set_special_state(TASK_PARKED); + if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags)) + break; + + /* + * Thread is going to call schedule(), do not preempt it, + * or the caller of kthread_park() may spend more time in + * wait_task_inactive(). + */ + preempt_disable(); + complete(&self->parked); + schedule_preempt_disabled(); + preempt_enable(); + } + __set_current_state(TASK_RUNNING); +} + +void kthread_parkme(void) +{ + __kthread_parkme(to_kthread(current)); +} +EXPORT_SYMBOL_GPL(kthread_parkme); + +/** + * kthread_exit - Cause the current kthread return @result to kthread_stop(). + * @result: The integer value to return to kthread_stop(). + * + * While kthread_exit can be called directly, it exists so that + * functions which do some additional work in non-modular code such as + * module_put_and_kthread_exit can be implemented. + * + * Does not return. + */ +void __noreturn kthread_exit(long result) +{ + struct kthread *kthread = to_kthread(current); + kthread->result = result; + do_exit(0); +} + +/** + * kthread_complete_and_exit - Exit the current kthread. + * @comp: Completion to complete + * @code: The integer value to return to kthread_stop(). + * + * If present, complete @comp and then return code to kthread_stop(). + * + * A kernel thread whose module may be removed after the completion of + * @comp can use this function to exit safely. + * + * Does not return. + */ +void __noreturn kthread_complete_and_exit(struct completion *comp, long code) +{ + if (comp) + complete(comp); + + kthread_exit(code); +} +EXPORT_SYMBOL(kthread_complete_and_exit); + +static int kthread(void *_create) +{ + static const struct sched_param param = { .sched_priority = 0 }; + /* Copy data: it's on kthread's stack */ + struct kthread_create_info *create = _create; + int (*threadfn)(void *data) = create->threadfn; + void *data = create->data; + struct completion *done; + struct kthread *self; + int ret; + + self = to_kthread(current); + + /* Release the structure when caller killed by a fatal signal. */ + done = xchg(&create->done, NULL); + if (!done) { + kfree(create->full_name); + kfree(create); + kthread_exit(-EINTR); + } + + self->full_name = create->full_name; + self->threadfn = threadfn; + self->data = data; + + /* + * The new thread inherited kthreadd's priority and CPU mask. Reset + * back to default in case they have been changed. + */ + sched_setscheduler_nocheck(current, SCHED_NORMAL, ¶m); + set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_KTHREAD)); + + /* OK, tell user we're spawned, wait for stop or wakeup */ + __set_current_state(TASK_UNINTERRUPTIBLE); + create->result = current; + /* + * Thread is going to call schedule(), do not preempt it, + * or the creator may spend more time in wait_task_inactive(). + */ + preempt_disable(); + complete(done); + schedule_preempt_disabled(); + preempt_enable(); + + ret = -EINTR; + if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) { + cgroup_kthread_ready(); + __kthread_parkme(self); + ret = threadfn(data); + } + kthread_exit(ret); +} + +/* called from kernel_clone() to get node information for about to be created task */ +int tsk_fork_get_node(struct task_struct *tsk) +{ +#ifdef CONFIG_NUMA + if (tsk == kthreadd_task) + return tsk->pref_node_fork; +#endif + return NUMA_NO_NODE; +} + +static void create_kthread(struct kthread_create_info *create) +{ + int pid; + +#ifdef CONFIG_NUMA + current->pref_node_fork = create->node; +#endif + /* We want our own signal handler (we take no signals by default). */ + pid = kernel_thread(kthread, create, create->full_name, + CLONE_FS | CLONE_FILES | SIGCHLD); + if (pid < 0) { + /* Release the structure when caller killed by a fatal signal. */ + struct completion *done = xchg(&create->done, NULL); + + kfree(create->full_name); + if (!done) { + kfree(create); + return; + } + create->result = ERR_PTR(pid); + complete(done); + } +} + +static __printf(4, 0) +struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data), + void *data, int node, + const char namefmt[], + va_list args) +{ + DECLARE_COMPLETION_ONSTACK(done); + struct task_struct *task; + struct kthread_create_info *create = kmalloc(sizeof(*create), + GFP_KERNEL); + + if (!create) + return ERR_PTR(-ENOMEM); + create->threadfn = threadfn; + create->data = data; + create->node = node; + create->done = &done; + create->full_name = kvasprintf(GFP_KERNEL, namefmt, args); + if (!create->full_name) { + task = ERR_PTR(-ENOMEM); + goto free_create; + } + + spin_lock(&kthread_create_lock); + list_add_tail(&create->list, &kthread_create_list); + spin_unlock(&kthread_create_lock); + + wake_up_process(kthreadd_task); + /* + * Wait for completion in killable state, for I might be chosen by + * the OOM killer while kthreadd is trying to allocate memory for + * new kernel thread. + */ + if (unlikely(wait_for_completion_killable(&done))) { + /* + * If I was killed by a fatal signal before kthreadd (or new + * kernel thread) calls complete(), leave the cleanup of this + * structure to that thread. + */ + if (xchg(&create->done, NULL)) + return ERR_PTR(-EINTR); + /* + * kthreadd (or new kernel thread) will call complete() + * shortly. + */ + wait_for_completion(&done); + } + task = create->result; +free_create: + kfree(create); + return task; +} + +/** + * kthread_create_on_node - create a kthread. + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @node: task and thread structures for the thread are allocated on this node + * @namefmt: printf-style name for the thread. + * + * Description: This helper function creates and names a kernel + * thread. The thread will be stopped: use wake_up_process() to start + * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and + * is affine to all CPUs. + * + * If thread is going to be bound on a particular cpu, give its node + * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE. + * When woken, the thread will run @threadfn() with @data as its + * argument. @threadfn() can either return directly if it is a + * standalone thread for which no one will call kthread_stop(), or + * return when 'kthread_should_stop()' is true (which means + * kthread_stop() has been called). The return value should be zero + * or a negative error number; it will be passed to kthread_stop(). + * + * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR). + */ +struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), + void *data, int node, + const char namefmt[], + ...) +{ + struct task_struct *task; + va_list args; + + va_start(args, namefmt); + task = __kthread_create_on_node(threadfn, data, node, namefmt, args); + va_end(args); + + return task; +} +EXPORT_SYMBOL(kthread_create_on_node); + +static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, unsigned int state) +{ + unsigned long flags; + + if (!wait_task_inactive(p, state)) { + WARN_ON(1); + return; + } + + /* It's safe because the task is inactive. */ + raw_spin_lock_irqsave(&p->pi_lock, flags); + do_set_cpus_allowed(p, mask); + p->flags |= PF_NO_SETAFFINITY; + raw_spin_unlock_irqrestore(&p->pi_lock, flags); +} + +static void __kthread_bind(struct task_struct *p, unsigned int cpu, unsigned int state) +{ + __kthread_bind_mask(p, cpumask_of(cpu), state); +} + +void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask) +{ + __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE); +} + +/** + * kthread_bind - bind a just-created kthread to a cpu. + * @p: thread created by kthread_create(). + * @cpu: cpu (might not be online, must be possible) for @k to run on. + * + * Description: This function is equivalent to set_cpus_allowed(), + * except that @cpu doesn't need to be online, and the thread must be + * stopped (i.e., just returned from kthread_create()). + */ +void kthread_bind(struct task_struct *p, unsigned int cpu) +{ + __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); +} +EXPORT_SYMBOL(kthread_bind); + +/** + * kthread_create_on_cpu - Create a cpu bound kthread + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @cpu: The cpu on which the thread should be bound, + * @namefmt: printf-style name for the thread. Format is restricted + * to "name.*%u". Code fills in cpu number. + * + * Description: This helper function creates and names a kernel thread + */ +struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), + void *data, unsigned int cpu, + const char *namefmt) +{ + struct task_struct *p; + + p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt, + cpu); + if (IS_ERR(p)) + return p; + kthread_bind(p, cpu); + /* CPU hotplug need to bind once again when unparking the thread. */ + to_kthread(p)->cpu = cpu; + return p; +} +EXPORT_SYMBOL(kthread_create_on_cpu); + +void kthread_set_per_cpu(struct task_struct *k, int cpu) +{ + struct kthread *kthread = to_kthread(k); + if (!kthread) + return; + + WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY)); + + if (cpu < 0) { + clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags); + return; + } + + kthread->cpu = cpu; + set_bit(KTHREAD_IS_PER_CPU, &kthread->flags); +} + +bool kthread_is_per_cpu(struct task_struct *p) +{ + struct kthread *kthread = __to_kthread(p); + if (!kthread) + return false; + + return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags); +} + +/** + * kthread_unpark - unpark a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_park() for @k to return false, wakes it, and + * waits for it to return. If the thread is marked percpu then its + * bound to the cpu again. + */ +void kthread_unpark(struct task_struct *k) +{ + struct kthread *kthread = to_kthread(k); + + /* + * Newly created kthread was parked when the CPU was offline. + * The binding was lost and we need to set it again. + */ + if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags)) + __kthread_bind(k, kthread->cpu, TASK_PARKED); + + clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); + /* + * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup. + */ + wake_up_state(k, TASK_PARKED); +} +EXPORT_SYMBOL_GPL(kthread_unpark); + +/** + * kthread_park - park a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_park() for @k to return true, wakes it, and + * waits for it to return. This can also be called after kthread_create() + * instead of calling wake_up_process(): the thread will park without + * calling threadfn(). + * + * Returns 0 if the thread is parked, -ENOSYS if the thread exited. + * If called by the kthread itself just the park bit is set. + */ +int kthread_park(struct task_struct *k) +{ + struct kthread *kthread = to_kthread(k); + + if (WARN_ON(k->flags & PF_EXITING)) + return -ENOSYS; + + if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags))) + return -EBUSY; + + set_bit(KTHREAD_SHOULD_PARK, &kthread->flags); + if (k != current) { + wake_up_process(k); + /* + * Wait for __kthread_parkme() to complete(), this means we + * _will_ have TASK_PARKED and are about to call schedule(). + */ + wait_for_completion(&kthread->parked); + /* + * Now wait for that schedule() to complete and the task to + * get scheduled out. + */ + WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED)); + } + + return 0; +} +EXPORT_SYMBOL_GPL(kthread_park); + +/** + * kthread_stop - stop a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_stop() for @k to return true, wakes it, and + * waits for it to exit. This can also be called after kthread_create() + * instead of calling wake_up_process(): the thread will exit without + * calling threadfn(). + * + * If threadfn() may call kthread_exit() itself, the caller must ensure + * task_struct can't go away. + * + * Returns the result of threadfn(), or %-EINTR if wake_up_process() + * was never called. + */ +int kthread_stop(struct task_struct *k) +{ + struct kthread *kthread; + int ret; + + trace_sched_kthread_stop(k); + + get_task_struct(k); + kthread = to_kthread(k); + set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); + kthread_unpark(k); + set_tsk_thread_flag(k, TIF_NOTIFY_SIGNAL); + wake_up_process(k); + wait_for_completion(&kthread->exited); + ret = kthread->result; + put_task_struct(k); + + trace_sched_kthread_stop_ret(ret); + return ret; +} +EXPORT_SYMBOL(kthread_stop); + +int kthreadd(void *unused) +{ + struct task_struct *tsk = current; + + /* Setup a clean context for our children to inherit. */ + set_task_comm(tsk, "kthreadd"); + ignore_signals(tsk); + set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_TYPE_KTHREAD)); + set_mems_allowed(node_states[N_MEMORY]); + + current->flags |= PF_NOFREEZE; + cgroup_init_kthreadd(); + + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + if (list_empty(&kthread_create_list)) + schedule(); + __set_current_state(TASK_RUNNING); + + spin_lock(&kthread_create_lock); + while (!list_empty(&kthread_create_list)) { + struct kthread_create_info *create; + + create = list_entry(kthread_create_list.next, + struct kthread_create_info, list); + list_del_init(&create->list); + spin_unlock(&kthread_create_lock); + + create_kthread(create); + + spin_lock(&kthread_create_lock); + } + spin_unlock(&kthread_create_lock); + } + + return 0; +} + +void __kthread_init_worker(struct kthread_worker *worker, + const char *name, + struct lock_class_key *key) +{ + memset(worker, 0, sizeof(struct kthread_worker)); + raw_spin_lock_init(&worker->lock); + lockdep_set_class_and_name(&worker->lock, key, name); + INIT_LIST_HEAD(&worker->work_list); + INIT_LIST_HEAD(&worker->delayed_work_list); +} +EXPORT_SYMBOL_GPL(__kthread_init_worker); + +/** + * kthread_worker_fn - kthread function to process kthread_worker + * @worker_ptr: pointer to initialized kthread_worker + * + * This function implements the main cycle of kthread worker. It processes + * work_list until it is stopped with kthread_stop(). It sleeps when the queue + * is empty. + * + * The works are not allowed to keep any locks, disable preemption or interrupts + * when they finish. There is defined a safe point for freezing when one work + * finishes and before a new one is started. + * + * Also the works must not be handled by more than one worker at the same time, + * see also kthread_queue_work(). + */ +int kthread_worker_fn(void *worker_ptr) +{ + struct kthread_worker *worker = worker_ptr; + struct kthread_work *work; + + /* + * FIXME: Update the check and remove the assignment when all kthread + * worker users are created using kthread_create_worker*() functions. + */ + WARN_ON(worker->task && worker->task != current); + worker->task = current; + + if (worker->flags & KTW_FREEZABLE) + set_freezable(); + +repeat: + set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ + + if (kthread_should_stop()) { + __set_current_state(TASK_RUNNING); + raw_spin_lock_irq(&worker->lock); + worker->task = NULL; + raw_spin_unlock_irq(&worker->lock); + return 0; + } + + work = NULL; + raw_spin_lock_irq(&worker->lock); + if (!list_empty(&worker->work_list)) { + work = list_first_entry(&worker->work_list, + struct kthread_work, node); + list_del_init(&work->node); + } + worker->current_work = work; + raw_spin_unlock_irq(&worker->lock); + + if (work) { + kthread_work_func_t func = work->func; + __set_current_state(TASK_RUNNING); + trace_sched_kthread_work_execute_start(work); + work->func(work); + /* + * Avoid dereferencing work after this point. The trace + * event only cares about the address. + */ + trace_sched_kthread_work_execute_end(work, func); + } else if (!freezing(current)) + schedule(); + + try_to_freeze(); + cond_resched(); + goto repeat; +} +EXPORT_SYMBOL_GPL(kthread_worker_fn); + +static __printf(3, 0) struct kthread_worker * +__kthread_create_worker(int cpu, unsigned int flags, + const char namefmt[], va_list args) +{ + struct kthread_worker *worker; + struct task_struct *task; + int node = NUMA_NO_NODE; + + worker = kzalloc(sizeof(*worker), GFP_KERNEL); + if (!worker) + return ERR_PTR(-ENOMEM); + + kthread_init_worker(worker); + + if (cpu >= 0) + node = cpu_to_node(cpu); + + task = __kthread_create_on_node(kthread_worker_fn, worker, + node, namefmt, args); + if (IS_ERR(task)) + goto fail_task; + + if (cpu >= 0) + kthread_bind(task, cpu); + + worker->flags = flags; + worker->task = task; + wake_up_process(task); + return worker; + +fail_task: + kfree(worker); + return ERR_CAST(task); +} + +/** + * kthread_create_worker - create a kthread worker + * @flags: flags modifying the default behavior of the worker + * @namefmt: printf-style name for the kthread worker (task). + * + * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM) + * when the needed structures could not get allocated, and ERR_PTR(-EINTR) + * when the caller was killed by a fatal signal. + */ +struct kthread_worker * +kthread_create_worker(unsigned int flags, const char namefmt[], ...) +{ + struct kthread_worker *worker; + va_list args; + + va_start(args, namefmt); + worker = __kthread_create_worker(-1, flags, namefmt, args); + va_end(args); + + return worker; +} +EXPORT_SYMBOL(kthread_create_worker); + +/** + * kthread_create_worker_on_cpu - create a kthread worker and bind it + * to a given CPU and the associated NUMA node. + * @cpu: CPU number + * @flags: flags modifying the default behavior of the worker + * @namefmt: printf-style name for the kthread worker (task). + * + * Use a valid CPU number if you want to bind the kthread worker + * to the given CPU and the associated NUMA node. + * + * A good practice is to add the cpu number also into the worker name. + * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu). + * + * CPU hotplug: + * The kthread worker API is simple and generic. It just provides a way + * to create, use, and destroy workers. + * + * It is up to the API user how to handle CPU hotplug. They have to decide + * how to handle pending work items, prevent queuing new ones, and + * restore the functionality when the CPU goes off and on. There are a + * few catches: + * + * - CPU affinity gets lost when it is scheduled on an offline CPU. + * + * - The worker might not exist when the CPU was off when the user + * created the workers. + * + * Good practice is to implement two CPU hotplug callbacks and to + * destroy/create the worker when the CPU goes down/up. + * + * Return: + * The pointer to the allocated worker on success, ERR_PTR(-ENOMEM) + * when the needed structures could not get allocated, and ERR_PTR(-EINTR) + * when the caller was killed by a fatal signal. + */ +struct kthread_worker * +kthread_create_worker_on_cpu(int cpu, unsigned int flags, + const char namefmt[], ...) +{ + struct kthread_worker *worker; + va_list args; + + va_start(args, namefmt); + worker = __kthread_create_worker(cpu, flags, namefmt, args); + va_end(args); + + return worker; +} +EXPORT_SYMBOL(kthread_create_worker_on_cpu); + +/* + * Returns true when the work could not be queued at the moment. + * It happens when it is already pending in a worker list + * or when it is being cancelled. + */ +static inline bool queuing_blocked(struct kthread_worker *worker, + struct kthread_work *work) +{ + lockdep_assert_held(&worker->lock); + + return !list_empty(&work->node) || work->canceling; +} + +static void kthread_insert_work_sanity_check(struct kthread_worker *worker, + struct kthread_work *work) +{ + lockdep_assert_held(&worker->lock); + WARN_ON_ONCE(!list_empty(&work->node)); + /* Do not use a work with >1 worker, see kthread_queue_work() */ + WARN_ON_ONCE(work->worker && work->worker != worker); +} + +/* insert @work before @pos in @worker */ +static void kthread_insert_work(struct kthread_worker *worker, + struct kthread_work *work, + struct list_head *pos) +{ + kthread_insert_work_sanity_check(worker, work); + + trace_sched_kthread_work_queue_work(worker, work); + + list_add_tail(&work->node, pos); + work->worker = worker; + if (!worker->current_work && likely(worker->task)) + wake_up_process(worker->task); +} + +/** + * kthread_queue_work - queue a kthread_work + * @worker: target kthread_worker + * @work: kthread_work to queue + * + * Queue @work to work processor @task for async execution. @task + * must have been created with kthread_worker_create(). Returns %true + * if @work was successfully queued, %false if it was already pending. + * + * Reinitialize the work if it needs to be used by another worker. + * For example, when the worker was stopped and started again. + */ +bool kthread_queue_work(struct kthread_worker *worker, + struct kthread_work *work) +{ + bool ret = false; + unsigned long flags; + + raw_spin_lock_irqsave(&worker->lock, flags); + if (!queuing_blocked(worker, work)) { + kthread_insert_work(worker, work, &worker->work_list); + ret = true; + } + raw_spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kthread_queue_work); + +/** + * kthread_delayed_work_timer_fn - callback that queues the associated kthread + * delayed work when the timer expires. + * @t: pointer to the expired timer + * + * The format of the function is defined by struct timer_list. + * It should have been called from irqsafe timer with irq already off. + */ +void kthread_delayed_work_timer_fn(struct timer_list *t) +{ + struct kthread_delayed_work *dwork = from_timer(dwork, t, timer); + struct kthread_work *work = &dwork->work; + struct kthread_worker *worker = work->worker; + unsigned long flags; + + /* + * This might happen when a pending work is reinitialized. + * It means that it is used a wrong way. + */ + if (WARN_ON_ONCE(!worker)) + return; + + raw_spin_lock_irqsave(&worker->lock, flags); + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); + + /* Move the work from worker->delayed_work_list. */ + WARN_ON_ONCE(list_empty(&work->node)); + list_del_init(&work->node); + if (!work->canceling) + kthread_insert_work(worker, work, &worker->work_list); + + raw_spin_unlock_irqrestore(&worker->lock, flags); +} +EXPORT_SYMBOL(kthread_delayed_work_timer_fn); + +static void __kthread_queue_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct timer_list *timer = &dwork->timer; + struct kthread_work *work = &dwork->work; + + WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn); + + /* + * 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) { + kthread_insert_work(worker, work, &worker->work_list); + return; + } + + /* Be paranoid and try to detect possible races already now. */ + kthread_insert_work_sanity_check(worker, work); + + list_add(&work->node, &worker->delayed_work_list); + work->worker = worker; + timer->expires = jiffies + delay; + add_timer(timer); +} + +/** + * kthread_queue_delayed_work - queue the associated kthread work + * after a delay. + * @worker: target kthread_worker + * @dwork: kthread_delayed_work to queue + * @delay: number of jiffies to wait before queuing + * + * If the work has not been pending it starts a timer that will queue + * the work after the given @delay. If @delay is zero, it queues the + * work immediately. + * + * Return: %false if the @work has already been pending. It means that + * either the timer was running or the work was queued. It returns %true + * otherwise. + */ +bool kthread_queue_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct kthread_work *work = &dwork->work; + unsigned long flags; + bool ret = false; + + raw_spin_lock_irqsave(&worker->lock, flags); + + if (!queuing_blocked(worker, work)) { + __kthread_queue_delayed_work(worker, dwork, delay); + ret = true; + } + + raw_spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kthread_queue_delayed_work); + +struct kthread_flush_work { + struct kthread_work work; + struct completion done; +}; + +static void kthread_flush_work_fn(struct kthread_work *work) +{ + struct kthread_flush_work *fwork = + container_of(work, struct kthread_flush_work, work); + complete(&fwork->done); +} + +/** + * kthread_flush_work - flush a kthread_work + * @work: work to flush + * + * If @work is queued or executing, wait for it to finish execution. + */ +void kthread_flush_work(struct kthread_work *work) +{ + struct kthread_flush_work fwork = { + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), + COMPLETION_INITIALIZER_ONSTACK(fwork.done), + }; + struct kthread_worker *worker; + bool noop = false; + + worker = work->worker; + if (!worker) + return; + + raw_spin_lock_irq(&worker->lock); + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); + + if (!list_empty(&work->node)) + kthread_insert_work(worker, &fwork.work, work->node.next); + else if (worker->current_work == work) + kthread_insert_work(worker, &fwork.work, + worker->work_list.next); + else + noop = true; + + raw_spin_unlock_irq(&worker->lock); + + if (!noop) + wait_for_completion(&fwork.done); +} +EXPORT_SYMBOL_GPL(kthread_flush_work); + +/* + * Make sure that the timer is neither set nor running and could + * not manipulate the work list_head any longer. + * + * The function is called under worker->lock. The lock is temporary + * released but the timer can't be set again in the meantime. + */ +static void kthread_cancel_delayed_work_timer(struct kthread_work *work, + unsigned long *flags) +{ + struct kthread_delayed_work *dwork = + container_of(work, struct kthread_delayed_work, work); + struct kthread_worker *worker = work->worker; + + /* + * del_timer_sync() must be called to make sure that the timer + * callback is not running. The lock must be temporary released + * to avoid a deadlock with the callback. In the meantime, + * any queuing is blocked by setting the canceling counter. + */ + work->canceling++; + raw_spin_unlock_irqrestore(&worker->lock, *flags); + del_timer_sync(&dwork->timer); + raw_spin_lock_irqsave(&worker->lock, *flags); + work->canceling--; +} + +/* + * This function removes the work from the worker queue. + * + * It is called under worker->lock. The caller must make sure that + * the timer used by delayed work is not running, e.g. by calling + * kthread_cancel_delayed_work_timer(). + * + * The work might still be in use when this function finishes. See the + * current_work proceed by the worker. + * + * Return: %true if @work was pending and successfully canceled, + * %false if @work was not pending + */ +static bool __kthread_cancel_work(struct kthread_work *work) +{ + /* + * Try to remove the work from a worker list. It might either + * be from worker->work_list or from worker->delayed_work_list. + */ + if (!list_empty(&work->node)) { + list_del_init(&work->node); + return true; + } + + return false; +} + +/** + * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work + * @worker: kthread worker to use + * @dwork: kthread delayed work to queue + * @delay: number of jiffies to wait before queuing + * + * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise, + * modify @dwork's timer so that it expires after @delay. If @delay is zero, + * @work is guaranteed to be queued immediately. + * + * Return: %false if @dwork was idle and queued, %true otherwise. + * + * A special case is when the work is being canceled in parallel. + * It might be caused either by the real kthread_cancel_delayed_work_sync() + * or yet another kthread_mod_delayed_work() call. We let the other command + * win and return %true here. The return value can be used for reference + * counting and the number of queued works stays the same. Anyway, the caller + * is supposed to synchronize these operations a reasonable way. + * + * This function is safe to call from any context including IRQ handler. + * See __kthread_cancel_work() and kthread_delayed_work_timer_fn() + * for details. + */ +bool kthread_mod_delayed_work(struct kthread_worker *worker, + struct kthread_delayed_work *dwork, + unsigned long delay) +{ + struct kthread_work *work = &dwork->work; + unsigned long flags; + int ret; + + raw_spin_lock_irqsave(&worker->lock, flags); + + /* Do not bother with canceling when never queued. */ + if (!work->worker) { + ret = false; + goto fast_queue; + } + + /* Work must not be used with >1 worker, see kthread_queue_work() */ + WARN_ON_ONCE(work->worker != worker); + + /* + * Temporary cancel the work but do not fight with another command + * that is canceling the work as well. + * + * It is a bit tricky because of possible races with another + * mod_delayed_work() and cancel_delayed_work() callers. + * + * The timer must be canceled first because worker->lock is released + * when doing so. But the work can be removed from the queue (list) + * only when it can be queued again so that the return value can + * be used for reference counting. + */ + kthread_cancel_delayed_work_timer(work, &flags); + if (work->canceling) { + /* The number of works in the queue does not change. */ + ret = true; + goto out; + } + ret = __kthread_cancel_work(work); + +fast_queue: + __kthread_queue_delayed_work(worker, dwork, delay); +out: + raw_spin_unlock_irqrestore(&worker->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kthread_mod_delayed_work); + +static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork) +{ + struct kthread_worker *worker = work->worker; + unsigned long flags; + int ret = false; + + if (!worker) + goto out; + + raw_spin_lock_irqsave(&worker->lock, flags); + /* Work must not be used with >1 worker, see kthread_queue_work(). */ + WARN_ON_ONCE(work->worker != worker); + + if (is_dwork) + kthread_cancel_delayed_work_timer(work, &flags); + + ret = __kthread_cancel_work(work); + + if (worker->current_work != work) + goto out_fast; + + /* + * The work is in progress and we need to wait with the lock released. + * In the meantime, block any queuing by setting the canceling counter. + */ + work->canceling++; + raw_spin_unlock_irqrestore(&worker->lock, flags); + kthread_flush_work(work); + raw_spin_lock_irqsave(&worker->lock, flags); + work->canceling--; + +out_fast: + raw_spin_unlock_irqrestore(&worker->lock, flags); +out: + return ret; +} + +/** + * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish + * @work: the kthread work to cancel + * + * Cancel @work and wait for its execution to finish. This function + * can be used even if the work re-queues itself. On return from this + * function, @work is guaranteed to be not pending or executing on any CPU. + * + * kthread_cancel_work_sync(&delayed_work->work) must not be used for + * delayed_work's. Use kthread_cancel_delayed_work_sync() instead. + * + * The caller must ensure that the worker on which @work was last + * queued can't be destroyed before this function returns. + * + * Return: %true if @work was pending, %false otherwise. + */ +bool kthread_cancel_work_sync(struct kthread_work *work) +{ + return __kthread_cancel_work_sync(work, false); +} +EXPORT_SYMBOL_GPL(kthread_cancel_work_sync); + +/** + * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and + * wait for it to finish. + * @dwork: the kthread delayed work to cancel + * + * This is kthread_cancel_work_sync() for delayed works. + * + * Return: %true if @dwork was pending, %false otherwise. + */ +bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork) +{ + return __kthread_cancel_work_sync(&dwork->work, true); +} +EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync); + +/** + * kthread_flush_worker - flush all current works on a kthread_worker + * @worker: worker to flush + * + * Wait until all currently executing or pending works on @worker are + * finished. + */ +void kthread_flush_worker(struct kthread_worker *worker) +{ + struct kthread_flush_work fwork = { + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), + COMPLETION_INITIALIZER_ONSTACK(fwork.done), + }; + + kthread_queue_work(worker, &fwork.work); + wait_for_completion(&fwork.done); +} +EXPORT_SYMBOL_GPL(kthread_flush_worker); + +/** + * kthread_destroy_worker - destroy a kthread worker + * @worker: worker to be destroyed + * + * Flush and destroy @worker. The simple flush is enough because the kthread + * worker API is used only in trivial scenarios. There are no multi-step state + * machines needed. + * + * Note that this function is not responsible for handling delayed work, so + * caller should be responsible for queuing or canceling all delayed work items + * before invoke this function. + */ +void kthread_destroy_worker(struct kthread_worker *worker) +{ + struct task_struct *task; + + task = worker->task; + if (WARN_ON(!task)) + return; + + kthread_flush_worker(worker); + kthread_stop(task); + WARN_ON(!list_empty(&worker->delayed_work_list)); + WARN_ON(!list_empty(&worker->work_list)); + kfree(worker); +} +EXPORT_SYMBOL(kthread_destroy_worker); + +/** + * kthread_use_mm - make the calling kthread operate on an address space + * @mm: address space to operate on + */ +void kthread_use_mm(struct mm_struct *mm) +{ + struct mm_struct *active_mm; + struct task_struct *tsk = current; + + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(tsk->mm); + + /* + * It is possible for mm to be the same as tsk->active_mm, but + * we must still mmgrab(mm) and mmdrop_lazy_tlb(active_mm), + * because these references are not equivalent. + */ + mmgrab(mm); + + task_lock(tsk); + /* Hold off tlb flush IPIs while switching mm's */ + local_irq_disable(); + active_mm = tsk->active_mm; + tsk->active_mm = mm; + tsk->mm = mm; + membarrier_update_current_mm(mm); + switch_mm_irqs_off(active_mm, mm, tsk); + local_irq_enable(); + task_unlock(tsk); +#ifdef finish_arch_post_lock_switch + finish_arch_post_lock_switch(); +#endif + + /* + * When a kthread starts operating on an address space, the loop + * in membarrier_{private,global}_expedited() may not observe + * that tsk->mm, and not issue an IPI. Membarrier requires a + * memory barrier after storing to tsk->mm, before accessing + * user-space memory. A full memory barrier for membarrier + * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by + * mmdrop_lazy_tlb(). + */ + mmdrop_lazy_tlb(active_mm); +} +EXPORT_SYMBOL_GPL(kthread_use_mm); + +/** + * kthread_unuse_mm - reverse the effect of kthread_use_mm() + * @mm: address space to operate on + */ +void kthread_unuse_mm(struct mm_struct *mm) +{ + struct task_struct *tsk = current; + + WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); + WARN_ON_ONCE(!tsk->mm); + + task_lock(tsk); + /* + * When a kthread stops operating on an address space, the loop + * in membarrier_{private,global}_expedited() may not observe + * that tsk->mm, and not issue an IPI. Membarrier requires a + * memory barrier after accessing user-space memory, before + * clearing tsk->mm. + */ + smp_mb__after_spinlock(); + sync_mm_rss(mm); + local_irq_disable(); + tsk->mm = NULL; + membarrier_update_current_mm(NULL); + mmgrab_lazy_tlb(mm); + /* active_mm is still 'mm' */ + enter_lazy_tlb(mm, tsk); + local_irq_enable(); + task_unlock(tsk); + + mmdrop(mm); +} +EXPORT_SYMBOL_GPL(kthread_unuse_mm); + +#ifdef CONFIG_BLK_CGROUP +/** + * kthread_associate_blkcg - associate blkcg to current kthread + * @css: the cgroup info + * + * Current thread must be a kthread. The thread is running jobs on behalf of + * other threads. In some cases, we expect the jobs attach cgroup info of + * original threads instead of that of current thread. This function stores + * original thread's cgroup info in current kthread context for later + * retrieval. + */ +void kthread_associate_blkcg(struct cgroup_subsys_state *css) +{ + struct kthread *kthread; + + if (!(current->flags & PF_KTHREAD)) + return; + kthread = to_kthread(current); + if (!kthread) + return; + + if (kthread->blkcg_css) { + css_put(kthread->blkcg_css); + kthread->blkcg_css = NULL; + } + if (css) { + css_get(css); + kthread->blkcg_css = css; + } +} +EXPORT_SYMBOL(kthread_associate_blkcg); + +/** + * kthread_blkcg - get associated blkcg css of current kthread + * + * Current thread must be a kthread. + */ +struct cgroup_subsys_state *kthread_blkcg(void) +{ + struct kthread *kthread; + + if (current->flags & PF_KTHREAD) { + kthread = to_kthread(current); + if (kthread) + return kthread->blkcg_css; + } + return NULL; +} +#endif |