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e73f8959 ON |
1 | #include <linux/spinlock.h> |
2 | #include <linux/task_work.h> | |
3 | #include <linux/tracehook.h> | |
4 | ||
9da33de6 ON |
5 | static struct callback_head work_exited; /* all we need is ->next == NULL */ |
6 | ||
e73f8959 | 7 | int |
ac3d0da8 | 8 | task_work_add(struct task_struct *task, struct callback_head *work, bool notify) |
e73f8959 | 9 | { |
ac3d0da8 | 10 | struct callback_head *head; |
9da33de6 | 11 | |
ac3d0da8 ON |
12 | do { |
13 | head = ACCESS_ONCE(task->task_works); | |
9da33de6 ON |
14 | if (unlikely(head == &work_exited)) |
15 | return -ESRCH; | |
ac3d0da8 ON |
16 | work->next = head; |
17 | } while (cmpxchg(&task->task_works, head, work) != head); | |
e73f8959 | 18 | |
ed3e694d | 19 | if (notify) |
e73f8959 | 20 | set_notify_resume(task); |
ed3e694d | 21 | return 0; |
e73f8959 ON |
22 | } |
23 | ||
67d12145 | 24 | struct callback_head * |
e73f8959 ON |
25 | task_work_cancel(struct task_struct *task, task_work_func_t func) |
26 | { | |
ac3d0da8 ON |
27 | struct callback_head **pprev = &task->task_works; |
28 | struct callback_head *work = NULL; | |
e73f8959 | 29 | unsigned long flags; |
ac3d0da8 ON |
30 | /* |
31 | * If cmpxchg() fails we continue without updating pprev. | |
32 | * Either we raced with task_work_add() which added the | |
33 | * new entry before this work, we will find it again. Or | |
9da33de6 | 34 | * we raced with task_work_run(), *pprev == NULL/exited. |
ac3d0da8 | 35 | */ |
e73f8959 | 36 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
ac3d0da8 ON |
37 | while ((work = ACCESS_ONCE(*pprev))) { |
38 | read_barrier_depends(); | |
39 | if (work->func != func) | |
40 | pprev = &work->next; | |
41 | else if (cmpxchg(pprev, work, work->next) == work) | |
42 | break; | |
e73f8959 | 43 | } |
e73f8959 | 44 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
ac3d0da8 ON |
45 | |
46 | return work; | |
e73f8959 ON |
47 | } |
48 | ||
49 | void task_work_run(void) | |
50 | { | |
51 | struct task_struct *task = current; | |
ac3d0da8 | 52 | struct callback_head *work, *head, *next; |
e73f8959 | 53 | |
ac3d0da8 | 54 | for (;;) { |
9da33de6 ON |
55 | /* |
56 | * work->func() can do task_work_add(), do not set | |
57 | * work_exited unless the list is empty. | |
58 | */ | |
59 | do { | |
60 | work = ACCESS_ONCE(task->task_works); | |
61 | head = !work && (task->flags & PF_EXITING) ? | |
62 | &work_exited : NULL; | |
63 | } while (cmpxchg(&task->task_works, work, head) != work); | |
64 | ||
ac3d0da8 ON |
65 | if (!work) |
66 | break; | |
67 | /* | |
68 | * Synchronize with task_work_cancel(). It can't remove | |
69 | * the first entry == work, cmpxchg(task_works) should | |
70 | * fail, but it can play with *work and other entries. | |
71 | */ | |
72 | raw_spin_unlock_wait(&task->pi_lock); | |
73 | smp_mb(); | |
e73f8959 | 74 | |
ac3d0da8 ON |
75 | /* Reverse the list to run the works in fifo order */ |
76 | head = NULL; | |
77 | do { | |
78 | next = work->next; | |
79 | work->next = head; | |
80 | head = work; | |
81 | work = next; | |
82 | } while (work); | |
e73f8959 | 83 | |
ac3d0da8 ON |
84 | work = head; |
85 | do { | |
86 | next = work->next; | |
87 | work->func(work); | |
88 | work = next; | |
f341861f | 89 | cond_resched(); |
ac3d0da8 | 90 | } while (work); |
e73f8959 ON |
91 | } |
92 | } |