| 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 | } |