93 lines
2.2 KiB
C
93 lines
2.2 KiB
C
#include <linux/spinlock.h>
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#include <linux/task_work.h>
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#include <linux/tracehook.h>
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static struct callback_head work_exited; /* all we need is ->next == NULL */
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int
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task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
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{
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struct callback_head *head;
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do {
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head = ACCESS_ONCE(task->task_works);
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if (unlikely(head == &work_exited))
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return -ESRCH;
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work->next = head;
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} while (cmpxchg(&task->task_works, head, work) != head);
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if (notify)
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set_notify_resume(task);
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return 0;
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}
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struct callback_head *
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task_work_cancel(struct task_struct *task, task_work_func_t func)
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{
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struct callback_head **pprev = &task->task_works;
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struct callback_head *work = NULL;
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unsigned long flags;
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/*
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* If cmpxchg() fails we continue without updating pprev.
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* Either we raced with task_work_add() which added the
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* new entry before this work, we will find it again. Or
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* we raced with task_work_run(), *pprev == NULL/exited.
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*/
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raw_spin_lock_irqsave(&task->pi_lock, flags);
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while ((work = ACCESS_ONCE(*pprev))) {
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read_barrier_depends();
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if (work->func != func)
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pprev = &work->next;
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else if (cmpxchg(pprev, work, work->next) == work)
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break;
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}
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raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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return work;
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}
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void task_work_run(void)
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{
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struct task_struct *task = current;
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struct callback_head *work, *head, *next;
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for (;;) {
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/*
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* work->func() can do task_work_add(), do not set
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* work_exited unless the list is empty.
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*/
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do {
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work = ACCESS_ONCE(task->task_works);
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head = !work && (task->flags & PF_EXITING) ?
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&work_exited : NULL;
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} while (cmpxchg(&task->task_works, work, head) != work);
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if (!work)
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break;
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/*
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* Synchronize with task_work_cancel(). It can't remove
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* the first entry == work, cmpxchg(task_works) should
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* fail, but it can play with *work and other entries.
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*/
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raw_spin_unlock_wait(&task->pi_lock);
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smp_mb();
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/* Reverse the list to run the works in fifo order */
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head = NULL;
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do {
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next = work->next;
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work->next = head;
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head = work;
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work = next;
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} while (work);
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work = head;
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do {
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next = work->next;
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work->func(work);
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work = next;
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cond_resched();
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} while (work);
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}
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}
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