| 1 | #include <linux/spinlock.h>
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| 2 | #include <linux/task_work.h>
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| 3 | #include <linux/tracehook.h>
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| 4 |
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| 5 | static struct callback_head work_exited;
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| 6 |
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| 7 | int
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| 8 | task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
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| 9 | {
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| 10 | struct callback_head *head;
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| 11 |
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| 12 | do {
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| 13 | head = ACCESS_ONCE(task->task_works);
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| 14 | if (unlikely(head == &work_exited))
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| 15 | return -ESRCH;
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| 16 | work->next = head;
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| 17 | } while (cmpxchg(&task->task_works, head, work) != head);
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| 18 |
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| 19 | if (notify)
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| 20 | set_notify_resume(task);
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| 21 | return 0;
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| 22 | }
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| 23 |
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| 24 | struct callback_head *
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| 25 | task_work_cancel(struct task_struct *task, task_work_func_t func)
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| 26 | {
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| 27 | struct callback_head **pprev = &task->task_works;
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| 28 | struct callback_head *work = NULL;
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| 29 | unsigned long flags;
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| 30 | |
| 31 | * If cmpxchg() fails we continue without updating pprev.
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| 32 | * Either we raced with task_work_add() which added the
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| 33 | * new entry before this work, we will find it again. Or
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| 34 | * we raced with task_work_run(), *pprev == NULL/exited.
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| 35 |
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| 36 | raw_spin_lock_irqsave(&task->pi_lock, flags);
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| 37 | while ((work = ACCESS_ONCE(*pprev))) {
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| 38 | read_barrier_depends();
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| 39 | if (work->func != func)
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| 40 | pprev = &work->next;
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| 41 | else if (cmpxchg(pprev, work, work->next) == work)
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| 42 | break;
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| 43 | }
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| 44 | raw_spin_unlock_irqrestore(&task->pi_lock, flags);
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| 45 |
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| 46 | return work;
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| 47 | }
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| 48 |
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| 49 | void task_work_run(void)
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| 50 | {
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| 51 | struct task_struct *task = current;
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| 52 | struct callback_head *work, *head, *next;
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| 53 |
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| 54 | for (;;) {
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| 55 | |
| 56 | * work->func() can do task_work_add(), do not set
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| 57 | * work_exited unless the list is empty.
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| 58 |
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| 59 | do {
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| 60 | work = ACCESS_ONCE(task->task_works);
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| 61 | head = !work && (task->flags & PF_EXITING) ?
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| 62 | &work_exited : NULL;
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| 63 | } while (cmpxchg(&task->task_works, work, head) != work);
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| 64 |
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| 65 | if (!work)
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| 66 | break;
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| 67 | |
| 68 | * Synchronize with task_work_cancel(). It can't remove
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| 69 | * the first entry == work, cmpxchg(task_works) should
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| 70 | * fail, but it can play with *work and other entries.
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| 71 |
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| 72 | raw_spin_unlock_wait(&task->pi_lock);
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| 73 | smp_mb();
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| 74 |
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| 75 |
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| 76 | head = NULL;
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| 77 | do {
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| 78 | next = work->next;
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| 79 | work->next = head;
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| 80 | head = work;
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| 81 | work = next;
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| 82 | } while (work);
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| 83 |
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| 84 | work = head;
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| 85 | do {
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| 86 | next = work->next;
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| 87 | work->func(work);
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| 88 | work = next;
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| 89 | cond_resched();
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| 90 | } while (work);
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| 91 | }
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| 92 | }
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