kernel/task_work.c

   1 #include <linux/spinlock.h>
   2 #include <linux/task_work.h>
   3 #include <linux/tracehook.h>
   4
   5 int
   6 task_work_add(struct task_struct *task, struct callback_head *twork, bool notify)
   7 {
   8         struct callback_head *last, *first;
   9         unsigned long flags;
  10
  11         /*
  12          * Not inserting the new work if the task has already passed
  13          * exit_task_work() is the responisbility of callers.
  14          */
  15         raw_spin_lock_irqsave(&task->pi_lock, flags);
  16         last = task->task_works;
  17         first = last ? last->next : twork;
  18         twork->next = first;
  19         if (last)
  20                 last->next = twork;
  21         task->task_works = twork;
  22         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
  23
  24         /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
  25         if (notify)
  26                 set_notify_resume(task);
  27         return 0;
  28 }
  29
  30 struct callback_head *
  31 task_work_cancel(struct task_struct *task, task_work_func_t func)
  32 {
  33         unsigned long flags;
  34         struct callback_head *last, *res = NULL;
  35
  36         raw_spin_lock_irqsave(&task->pi_lock, flags);
  37         last = task->task_works;
  38         if (last) {
  39                 struct callback_head *q = last, *p = q->next;
  40                 while (1) {
  41                         if (p->func == func) {
  42                                 q->next = p->next;
  43                                 if (p == last)
  44                                         task->task_works = q == p ? NULL : q;
  45                                 res = p;
  46                                 break;
  47                         }
  48                         if (p == last)
  49                                 break;
  50                         q = p;
  51                         p = q->next;
  52                 }
  53         }
  54         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
  55         return res;
  56 }
  57
  58 void task_work_run(void)
  59 {
  60         struct task_struct *task = current;
  61         struct callback_head *p, *q;
  62
  63         while (1) {
  64                 raw_spin_lock_irq(&task->pi_lock);
  65                 p = task->task_works;
  66                 task->task_works = NULL;
  67                 raw_spin_unlock_irq(&task->pi_lock);
  68
  69                 if (unlikely(!p))
  70                         return;
  71
  72                 q = p->next; /* head */
  73                 p->next = NULL; /* cut it */
  74                 while (q) {
  75                         p = q->next;
  76                         q->func(q);
  77                         q = p;
  78                 }
  79         }
  80 }