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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 | ||
892f6668 ON |
7 | /** |
8 | * task_work_add - ask the @task to execute @work->func() | |
9 | * @task: the task which should run the callback | |
10 | * @work: the callback to run | |
11 | * @notify: send the notification if true | |
12 | * | |
13 | * Queue @work for task_work_run() below and notify the @task if @notify. | |
14 | * Fails if the @task is exiting/exited and thus it can't process this @work. | |
15 | * Otherwise @work->func() will be called when the @task returns from kernel | |
16 | * mode or exits. | |
17 | * | |
18 | * This is like the signal handler which runs in kernel mode, but it doesn't | |
19 | * try to wake up the @task. | |
20 | * | |
c8219906 ED |
21 | * Note: there is no ordering guarantee on works queued here. |
22 | * | |
892f6668 ON |
23 | * RETURNS: |
24 | * 0 if succeeds or -ESRCH. | |
25 | */ | |
e73f8959 | 26 | int |
ac3d0da8 | 27 | task_work_add(struct task_struct *task, struct callback_head *work, bool notify) |
e73f8959 | 28 | { |
ac3d0da8 | 29 | struct callback_head *head; |
9da33de6 | 30 | |
ac3d0da8 | 31 | do { |
61e96496 | 32 | head = READ_ONCE(task->task_works); |
9da33de6 ON |
33 | if (unlikely(head == &work_exited)) |
34 | return -ESRCH; | |
ac3d0da8 ON |
35 | work->next = head; |
36 | } while (cmpxchg(&task->task_works, head, work) != head); | |
e73f8959 | 37 | |
ed3e694d | 38 | if (notify) |
e73f8959 | 39 | set_notify_resume(task); |
ed3e694d | 40 | return 0; |
e73f8959 ON |
41 | } |
42 | ||
892f6668 ON |
43 | /** |
44 | * task_work_cancel - cancel a pending work added by task_work_add() | |
45 | * @task: the task which should execute the work | |
46 | * @func: identifies the work to remove | |
47 | * | |
48 | * Find the last queued pending work with ->func == @func and remove | |
49 | * it from queue. | |
50 | * | |
51 | * RETURNS: | |
52 | * The found work or NULL if not found. | |
53 | */ | |
67d12145 | 54 | struct callback_head * |
e73f8959 ON |
55 | task_work_cancel(struct task_struct *task, task_work_func_t func) |
56 | { | |
ac3d0da8 | 57 | struct callback_head **pprev = &task->task_works; |
205e550a | 58 | struct callback_head *work; |
e73f8959 | 59 | unsigned long flags; |
61e96496 ON |
60 | |
61 | if (likely(!task->task_works)) | |
62 | return NULL; | |
ac3d0da8 ON |
63 | /* |
64 | * If cmpxchg() fails we continue without updating pprev. | |
65 | * Either we raced with task_work_add() which added the | |
66 | * new entry before this work, we will find it again. Or | |
9da33de6 | 67 | * we raced with task_work_run(), *pprev == NULL/exited. |
ac3d0da8 | 68 | */ |
e73f8959 | 69 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
61e96496 | 70 | while ((work = lockless_dereference(*pprev))) { |
ac3d0da8 ON |
71 | if (work->func != func) |
72 | pprev = &work->next; | |
73 | else if (cmpxchg(pprev, work, work->next) == work) | |
74 | break; | |
e73f8959 | 75 | } |
e73f8959 | 76 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
ac3d0da8 ON |
77 | |
78 | return work; | |
e73f8959 ON |
79 | } |
80 | ||
892f6668 ON |
81 | /** |
82 | * task_work_run - execute the works added by task_work_add() | |
83 | * | |
84 | * Flush the pending works. Should be used by the core kernel code. | |
85 | * Called before the task returns to the user-mode or stops, or when | |
86 | * it exits. In the latter case task_work_add() can no longer add the | |
87 | * new work after task_work_run() returns. | |
88 | */ | |
e73f8959 ON |
89 | void task_work_run(void) |
90 | { | |
91 | struct task_struct *task = current; | |
ac3d0da8 | 92 | struct callback_head *work, *head, *next; |
e73f8959 | 93 | |
ac3d0da8 | 94 | for (;;) { |
9da33de6 ON |
95 | /* |
96 | * work->func() can do task_work_add(), do not set | |
97 | * work_exited unless the list is empty. | |
98 | */ | |
99 | do { | |
61e96496 | 100 | work = READ_ONCE(task->task_works); |
9da33de6 ON |
101 | head = !work && (task->flags & PF_EXITING) ? |
102 | &work_exited : NULL; | |
103 | } while (cmpxchg(&task->task_works, work, head) != work); | |
104 | ||
ac3d0da8 ON |
105 | if (!work) |
106 | break; | |
107 | /* | |
108 | * Synchronize with task_work_cancel(). It can't remove | |
109 | * the first entry == work, cmpxchg(task_works) should | |
110 | * fail, but it can play with *work and other entries. | |
111 | */ | |
112 | raw_spin_unlock_wait(&task->pi_lock); | |
e73f8959 | 113 | |
ac3d0da8 ON |
114 | do { |
115 | next = work->next; | |
116 | work->func(work); | |
117 | work = next; | |
f341861f | 118 | cond_resched(); |
ac3d0da8 | 119 | } while (work); |
e73f8959 ON |
120 | } |
121 | } |