kthread.c 32.2 KB
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/* Kernel thread helper functions.
 *   Copyright (C) 2004 IBM Corporation, Rusty Russell.
 *
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 * Creation is done via kthreadd, so that we get a clean environment
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 * even if we're invoked from userspace (think modprobe, hotplug cpu,
 * etc.).
 */
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#include <uapi/linux/sched/types.h>
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#include <linux/sched.h>
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#include <linux/sched/task.h>
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#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
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#include <linux/cpuset.h>
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#include <linux/unistd.h>
#include <linux/file.h>
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#include <linux/export.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
#include <linux/freezer.h>
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#include <linux/ptrace.h>
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#include <linux/uaccess.h>
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#include <linux/cgroup.h>
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#include <trace/events/sched.h>
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static DEFINE_SPINLOCK(kthread_create_lock);
static LIST_HEAD(kthread_create_list);
struct task_struct *kthreadd_task;
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struct kthread_create_info
{
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	/* Information passed to kthread() from kthreadd. */
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	int (*threadfn)(void *data);
	void *data;
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	int node;
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	/* Result passed back to kthread_create() from kthreadd. */
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	struct task_struct *result;
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	struct completion *done;
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	struct list_head list;
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};

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struct kthread {
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	unsigned long flags;
	unsigned int cpu;
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	void *data;
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	struct completion parked;
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	struct completion exited;
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};

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enum KTHREAD_BITS {
	KTHREAD_IS_PER_CPU = 0,
	KTHREAD_SHOULD_STOP,
	KTHREAD_SHOULD_PARK,
	KTHREAD_IS_PARKED,
};

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static inline void set_kthread_struct(void *kthread)
{
	/*
	 * We abuse ->set_child_tid to avoid the new member and because it
	 * can't be wrongly copied by copy_process(). We also rely on fact
	 * that the caller can't exec, so PF_KTHREAD can't be cleared.
	 */
	current->set_child_tid = (__force void __user *)kthread;
}
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static inline struct kthread *to_kthread(struct task_struct *k)
{
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	WARN_ON(!(k->flags & PF_KTHREAD));
	return (__force void *)k->set_child_tid;
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}

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void free_kthread_struct(struct task_struct *k)
{
	/*
	 * Can be NULL if this kthread was created by kernel_thread()
	 * or if kmalloc() in kthread() failed.
	 */
	kfree(to_kthread(k));
}

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/**
 * kthread_should_stop - should this kthread return now?
 *
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 * When someone calls kthread_stop() on your kthread, it will be woken
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 * and this will return true.  You should then return, and your return
 * value will be passed through to kthread_stop().
 */
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bool kthread_should_stop(void)
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{
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	return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
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}
EXPORT_SYMBOL(kthread_should_stop);

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/**
 * 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 test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
}
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EXPORT_SYMBOL_GPL(kthread_should_park);
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/**
 * 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);

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/**
 * 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;
}

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/**
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 * kthread_probe_data - speculative version of kthread_data()
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 * @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.
 */
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void *kthread_probe_data(struct task_struct *task)
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{
	struct kthread *kthread = to_kthread(task);
	void *data = NULL;

	probe_kernel_read(&data, &kthread->data, sizeof(data));
	return data;
}

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static void __kthread_parkme(struct kthread *self)
{
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	for (;;) {
		set_current_state(TASK_PARKED);
		if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
			break;
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		if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
			complete(&self->parked);
		schedule();
	}
	clear_bit(KTHREAD_IS_PARKED, &self->flags);
	__set_current_state(TASK_RUNNING);
}

void kthread_parkme(void)
{
	__kthread_parkme(to_kthread(current));
}
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EXPORT_SYMBOL_GPL(kthread_parkme);
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static int kthread(void *_create)
{
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	/* Copy data: it's on kthread's stack */
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	struct kthread_create_info *create = _create;
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	int (*threadfn)(void *data) = create->threadfn;
	void *data = create->data;
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	struct completion *done;
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	struct kthread *self;
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	int ret;
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	self = kmalloc(sizeof(*self), GFP_KERNEL);
	set_kthread_struct(self);
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	/* If user was SIGKILLed, I release the structure. */
	done = xchg(&create->done, NULL);
	if (!done) {
		kfree(create);
		do_exit(-EINTR);
	}
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	if (!self) {
		create->result = ERR_PTR(-ENOMEM);
		complete(done);
		do_exit(-ENOMEM);
	}

	self->flags = 0;
	self->data = data;
	init_completion(&self->exited);
	init_completion(&self->parked);
	current->vfork_done = &self->exited;

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	/* OK, tell user we're spawned, wait for stop or wakeup */
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	__set_current_state(TASK_UNINTERRUPTIBLE);
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	create->result = current;
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	complete(done);
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	schedule();

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	ret = -EINTR;
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	if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
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		cgroup_kthread_ready();
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		__kthread_parkme(self);
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		ret = threadfn(data);
	}
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	do_exit(ret);
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}

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/* called from do_fork() 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
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	return NUMA_NO_NODE;
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}

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static void create_kthread(struct kthread_create_info *create)
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{
	int pid;

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#ifdef CONFIG_NUMA
	current->pref_node_fork = create->node;
#endif
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	/* We want our own signal handler (we take no signals by default). */
	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
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	if (pid < 0) {
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		/* If user was SIGKILLed, I release the structure. */
		struct completion *done = xchg(&create->done, NULL);

		if (!done) {
			kfree(create);
			return;
		}
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		create->result = ERR_PTR(pid);
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		complete(done);
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	}
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}

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static __printf(4, 0)
struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
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						    void *data, int node,
						    const char namefmt[],
						    va_list args)
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{
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	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;
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	spin_lock(&kthread_create_lock);
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	list_add_tail(&create->list, &kthread_create_list);
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	spin_unlock(&kthread_create_lock);

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	wake_up_process(kthreadd_task);
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	/*
	 * 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 SIGKILLed before kthreadd (or new kernel thread)
		 * calls complete(), leave the cleanup of this structure to
		 * that thread.
		 */
		if (xchg(&create->done, NULL))
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			return ERR_PTR(-EINTR);
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		/*
		 * kthreadd (or new kernel thread) will call complete()
		 * shortly.
		 */
		wait_for_completion(&done);
	}
	task = create->result;
	if (!IS_ERR(task)) {
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		static const struct sched_param param = { .sched_priority = 0 };
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		char name[TASK_COMM_LEN];
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		/*
		 * task is already visible to other tasks, so updating
		 * COMM must be protected.
		 */
		vsnprintf(name, sizeof(name), namefmt, args);
		set_task_comm(task, name);
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		/*
		 * root may have changed our (kthreadd's) priority or CPU mask.
		 * The kernel thread should not inherit these properties.
		 */
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		sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
		set_cpus_allowed_ptr(task, cpu_all_mask);
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	}
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	kfree(create);
	return task;
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}
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/**
 * 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 call do_exit() 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;
}
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EXPORT_SYMBOL(kthread_create_on_node);
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static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
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{
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	unsigned long flags;

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	if (!wait_task_inactive(p, state)) {
		WARN_ON(1);
		return;
	}
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	/* It's safe because the task is inactive. */
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	raw_spin_lock_irqsave(&p->pi_lock, flags);
	do_set_cpus_allowed(p, mask);
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	p->flags |= PF_NO_SETAFFINITY;
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	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}

static void __kthread_bind(struct task_struct *p, unsigned int cpu, long 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);
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}

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/**
 * 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)
{
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	__kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
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}
EXPORT_SYMBOL(kthread_bind);

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/**
 * 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
 * The thread will be woken and put into park mode.
 */
struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
					  void *data, unsigned int cpu,
					  const char *namefmt)
{
	struct task_struct *p;

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	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
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				   cpu);
	if (IS_ERR(p))
		return p;
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	kthread_bind(p, cpu);
	/* CPU hotplug need to bind once again when unparking the thread. */
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	set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
	to_kthread(p)->cpu = cpu;
	return p;
}

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/**
 * 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)
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{
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	struct kthread *kthread = to_kthread(k);

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	clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
	/*
	 * We clear the IS_PARKED bit here as we don't wait
	 * until the task has left the park code. So if we'd
	 * park before that happens we'd see the IS_PARKED bit
	 * which might be about to be cleared.
	 */
	if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
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		/*
		 * Newly created kthread was parked when the CPU was offline.
		 * The binding was lost and we need to set it again.
		 */
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		if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
			__kthread_bind(k, kthread->cpu, TASK_PARKED);
		wake_up_state(k, TASK_PARKED);
	}
}
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EXPORT_SYMBOL_GPL(kthread_unpark);
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/**
 * 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)
{
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	struct kthread *kthread = to_kthread(k);

	if (WARN_ON(k->flags & PF_EXITING))
		return -ENOSYS;

	if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
		set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
		if (k != current) {
			wake_up_process(k);
			wait_for_completion(&kthread->parked);
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		}
	}
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	return 0;
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}
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EXPORT_SYMBOL_GPL(kthread_park);
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/**
 * 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
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 * 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 do_exit() itself, the caller must ensure
 * task_struct can't go away.
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 *
 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
 * was never called.
 */
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int kthread_stop(struct task_struct *k)
{
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	struct kthread *kthread;
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	int ret;

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	trace_sched_kthread_stop(k);
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	get_task_struct(k);
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	kthread = to_kthread(k);
	set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
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	kthread_unpark(k);
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	wake_up_process(k);
	wait_for_completion(&kthread->exited);
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	ret = k->exit_code;
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	put_task_struct(k);
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	trace_sched_kthread_stop_ret(ret);
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	return ret;
}
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EXPORT_SYMBOL(kthread_stop);
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int kthreadd(void *unused)
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{
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	struct task_struct *tsk = current;
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	/* Setup a clean context for our children to inherit. */
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	set_task_comm(tsk, "kthreadd");
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	ignore_signals(tsk);
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	set_cpus_allowed_ptr(tsk, cpu_all_mask);
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	set_mems_allowed(node_states[N_MEMORY]);
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	current->flags |= PF_NOFREEZE;
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	cgroup_init_kthreadd();
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	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;
}
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void __kthread_init_worker(struct kthread_worker *worker,
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				const char *name,
				struct lock_class_key *key)
{
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	memset(worker, 0, sizeof(struct kthread_worker));
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	spin_lock_init(&worker->lock);
	lockdep_set_class_and_name(&worker->lock, key, name);
	INIT_LIST_HEAD(&worker->work_list);
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	INIT_LIST_HEAD(&worker->delayed_work_list);
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}
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EXPORT_SYMBOL_GPL(__kthread_init_worker);
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/**
 * kthread_worker_fn - kthread function to process kthread_worker
 * @worker_ptr: pointer to initialized kthread_worker
 *
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 * 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.
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 *
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 * 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.
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 *
 * Also the works must not be handled by more than one worker at the same time,
 * see also kthread_queue_work().
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 */
int kthread_worker_fn(void *worker_ptr)
{
	struct kthread_worker *worker = worker_ptr;
	struct kthread_work *work;

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	/*
	 * 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);
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	worker->task = current;
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	if (worker->flags & KTW_FREEZABLE)
		set_freezable();

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repeat:
	set_current_state(TASK_INTERRUPTIBLE);	/* mb paired w/ kthread_stop */

	if (kthread_should_stop()) {
		__set_current_state(TASK_RUNNING);
		spin_lock_irq(&worker->lock);
		worker->task = NULL;
		spin_unlock_irq(&worker->lock);
		return 0;
	}

	work = NULL;
	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);
	}
637
	worker->current_work = work;
638 639 640 641 642 643 644 645 646
	spin_unlock_irq(&worker->lock);

	if (work) {
		__set_current_state(TASK_RUNNING);
		work->func(work);
	} else if (!freezing(current))
		schedule();

	try_to_freeze();
647
	cond_resched();
648 649 650 651
	goto repeat;
}
EXPORT_SYMBOL_GPL(kthread_worker_fn);

652
static __printf(3, 0) struct kthread_worker *
653 654
__kthread_create_worker(int cpu, unsigned int flags,
			const char namefmt[], va_list args)
655 656 657
{
	struct kthread_worker *worker;
	struct task_struct *task;
658
	int node = -1;
659 660 661 662 663 664 665

	worker = kzalloc(sizeof(*worker), GFP_KERNEL);
	if (!worker)
		return ERR_PTR(-ENOMEM);

	kthread_init_worker(worker);

666 667
	if (cpu >= 0)
		node = cpu_to_node(cpu);
668

669 670
	task = __kthread_create_on_node(kthread_worker_fn, worker,
						node, namefmt, args);
671 672 673
	if (IS_ERR(task))
		goto fail_task;

674 675 676
	if (cpu >= 0)
		kthread_bind(task, cpu);

677
	worker->flags = flags;
678 679 680 681 682 683 684 685 686 687 688
	worker->task = task;
	wake_up_process(task);
	return worker;

fail_task:
	kfree(worker);
	return ERR_CAST(task);
}

/**
 * kthread_create_worker - create a kthread worker
689
 * @flags: flags modifying the default behavior of the worker
690 691 692 693 694 695 696
 * @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 worker was SIGKILLed.
 */
struct kthread_worker *
697
kthread_create_worker(unsigned int flags, const char namefmt[], ...)
698 699 700 701 702
{
	struct kthread_worker *worker;
	va_list args;

	va_start(args, namefmt);
703
	worker = __kthread_create_worker(-1, flags, namefmt, args);
704 705 706 707 708 709 710 711 712 713
	va_end(args);

	return worker;
}
EXPORT_SYMBOL(kthread_create_worker);

/**
 * kthread_create_worker_on_cpu - create a kthread worker and bind it
 *	it to a given CPU and the associated NUMA node.
 * @cpu: CPU number
714
 * @flags: flags modifying the default behavior of the worker
715 716 717 718 719 720 721 722 723 724 725 726 727
 * @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).
 *
 * 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 worker was SIGKILLed.
 */
struct kthread_worker *
728 729
kthread_create_worker_on_cpu(int cpu, unsigned int flags,
			     const char namefmt[], ...)
730 731 732 733 734
{
	struct kthread_worker *worker;
	va_list args;

	va_start(args, namefmt);
735
	worker = __kthread_create_worker(cpu, flags, namefmt, args);
736 737 738 739 740 741
	va_end(args);

	return worker;
}
EXPORT_SYMBOL(kthread_create_worker_on_cpu);

742 743 744 745 746 747 748 749 750 751 752 753 754
/*
 * 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;
}

755 756 757 758 759 760 761 762 763
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);
}

764
/* insert @work before @pos in @worker */
765
static void kthread_insert_work(struct kthread_worker *worker,
766 767
				struct kthread_work *work,
				struct list_head *pos)
768
{
769
	kthread_insert_work_sanity_check(worker, work);
770 771

	list_add_tail(&work->node, pos);
772
	work->worker = worker;
773
	if (!worker->current_work && likely(worker->task))
774 775 776
		wake_up_process(worker->task);
}

777
/**
778
 * kthread_queue_work - queue a kthread_work
779 780 781 782 783 784
 * @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.
785 786 787
 *
 * Reinitialize the work if it needs to be used by another worker.
 * For example, when the worker was stopped and started again.
788
 */
789
bool kthread_queue_work(struct kthread_worker *worker,
790 791 792 793 794 795
			struct kthread_work *work)
{
	bool ret = false;
	unsigned long flags;

	spin_lock_irqsave(&worker->lock, flags);
796
	if (!queuing_blocked(worker, work)) {
797
		kthread_insert_work(worker, work, &worker->work_list);
798 799 800 801 802
		ret = true;
	}
	spin_unlock_irqrestore(&worker->lock, flags);
	return ret;
}
803
EXPORT_SYMBOL_GPL(kthread_queue_work);
804

805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894
/**
 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
 *	delayed work when the timer expires.
 * @__data: pointer to the data associated with the 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(unsigned long __data)
{
	struct kthread_delayed_work *dwork =
		(struct kthread_delayed_work *)__data;
	struct kthread_work *work = &dwork->work;
	struct kthread_worker *worker = work->worker;

	/*
	 * This might happen when a pending work is reinitialized.
	 * It means that it is used a wrong way.
	 */
	if (WARN_ON_ONCE(!worker))
		return;

	spin_lock(&worker->lock);
	/* 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);
	kthread_insert_work(worker, work, &worker->work_list);

	spin_unlock(&worker->lock);
}
EXPORT_SYMBOL(kthread_delayed_work_timer_fn);

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 ||
		     timer->data != (unsigned long)dwork);

	/*
	 * 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;

	spin_lock_irqsave(&worker->lock, flags);

895
	if (!queuing_blocked(worker, work)) {
896 897 898 899 900 901 902 903 904
		__kthread_queue_delayed_work(worker, dwork, delay);
		ret = true;
	}

	spin_unlock_irqrestore(&worker->lock, flags);
	return ret;
}
EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);

905 906 907 908 909 910 911 912 913 914 915 916
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);
}

917
/**
918
 * kthread_flush_work - flush a kthread_work
919 920 921 922
 * @work: work to flush
 *
 * If @work is queued or executing, wait for it to finish execution.
 */
923
void kthread_flush_work(struct kthread_work *work)
924
{
925 926 927 928 929 930 931 932 933 934
	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;
935

936
	spin_lock_irq(&worker->lock);
937 938
	/* Work must not be used with >1 worker, see kthread_queue_work(). */
	WARN_ON_ONCE(work->worker != worker);
939

940
	if (!list_empty(&work->node))
941
		kthread_insert_work(worker, &fwork.work, work->node.next);
942
	else if (worker->current_work == work)
943 944
		kthread_insert_work(worker, &fwork.work,
				    worker->work_list.next);
945 946
	else
		noop = true;
947

948
	spin_unlock_irq(&worker->lock);
949

950 951
	if (!noop)
		wait_for_completion(&fwork.done);
952
}
953
EXPORT_SYMBOL_GPL(kthread_flush_work);
954

955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998
/*
 * This function removes the work from the worker queue. Also it makes sure
 * that it won't get queued later via the delayed work's 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, bool is_dwork,
				  unsigned long *flags)
{
	/* Try to cancel the timer if exists. */
	if (is_dwork) {
		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++;
		spin_unlock_irqrestore(&worker->lock, *flags);
		del_timer_sync(&dwork->timer);
		spin_lock_irqsave(&worker->lock, *flags);
		work->canceling--;
	}

	/*
	 * 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;
}

999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051
/**
 * 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: %true if @dwork was pending and its timer was modified,
 * %false 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 %false here. 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 = false;

	spin_lock_irqsave(&worker->lock, flags);

	/* Do not bother with canceling when never queued. */
	if (!work->worker)
		goto fast_queue;

	/* Work must not be used with >1 worker, see kthread_queue_work() */
	WARN_ON_ONCE(work->worker != worker);

	/* Do not fight with another command that is canceling this work. */
	if (work->canceling)
		goto out;

	ret = __kthread_cancel_work(work, true, &flags);
fast_queue:
	__kthread_queue_delayed_work(worker, dwork, delay);
out:
	spin_unlock_irqrestore(&worker->lock, flags);
	return ret;
}
EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);

1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122
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;

	spin_lock_irqsave(&worker->lock, flags);
	/* Work must not be used with >1 worker, see kthread_queue_work(). */
	WARN_ON_ONCE(work->worker != worker);

	ret = __kthread_cancel_work(work, is_dwork, &flags);

	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++;
	spin_unlock_irqrestore(&worker->lock, flags);
	kthread_flush_work(work);
	spin_lock_irqsave(&worker->lock, flags);
	work->canceling--;

out_fast:
	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);

1123
/**
1124
 * kthread_flush_worker - flush all current works on a kthread_worker
1125 1126 1127 1128 1129
 * @worker: worker to flush
 *
 * Wait until all currently executing or pending works on @worker are
 * finished.
 */
1130
void kthread_flush_worker(struct kthread_worker *worker)
1131 1132 1133 1134 1135 1136
{
	struct kthread_flush_work fwork = {
		KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
		COMPLETION_INITIALIZER_ONSTACK(fwork.done),
	};

1137
	kthread_queue_work(worker, &fwork.work);
1138 1139
	wait_for_completion(&fwork.done);
}
1140
EXPORT_SYMBOL_GPL(kthread_flush_worker);
1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163

/**
 * 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.
 */
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->work_list));
	kfree(worker);
}
EXPORT_SYMBOL(kthread_destroy_worker);