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1 | #include <linux/spinlock.h> |
2 | #include <linux/task_work.h> |
3 | #include <linux/tracehook.h> |
4 | |
5 | static struct callback_head work_exited; /* all we need is ->next == NULL */ |
6 | |
7 | int |
8 | task_work_add(struct task_struct *task, struct callback_head *work, bool notify) |
9 | { |
10 | struct callback_head *head; |
11 | |
12 | do { |
13 | head = ACCESS_ONCE(task->task_works); |
14 | if (unlikely(head == &work_exited)) |
15 | return -ESRCH; |
16 | work->next = head; |
17 | } while (cmpxchg(&task->task_works, head, work) != head); |
18 | |
19 | if (notify) |
20 | set_notify_resume(task); |
21 | return 0; |
22 | } |
23 | |
24 | struct callback_head * |
25 | task_work_cancel(struct task_struct *task, task_work_func_t func) |
26 | { |
27 | struct callback_head **pprev = &task->task_works; |
28 | struct callback_head *work = NULL; |
29 | unsigned long flags; |
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 |
34 | * we raced with task_work_run(), *pprev == NULL/exited. |
35 | */ |
36 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
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; |
43 | } |
44 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
45 | |
46 | return work; |
47 | } |
48 | |
49 | void task_work_run(void) |
50 | { |
51 | struct task_struct *task = current; |
52 | struct callback_head *work, *head, *next; |
53 | |
54 | for (;;) { |
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 | |
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(); |
74 | |
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); |
83 | |
84 | work = head; |
85 | do { |
86 | next = work->next; |
87 | work->func(work); |
88 | work = next; |
89 | cond_resched(); |
90 | } while (work); |
91 | } |
92 | } |
93 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9