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 task_work *twork, bool notify)
   7 {
   8         unsigned long flags;
   9         int err = -ESRCH;
  10
  11 #ifndef TIF_NOTIFY_RESUME
  12         if (notify)
  13                 return -ENOTSUPP;
  14 #endif
  15         /*
  16          * We must not insert the new work if the task has already passed
  17          * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
  18          * and check PF_EXITING under pi_lock.
  19          */
  20         raw_spin_lock_irqsave(&task->pi_lock, flags);
  21         if (likely(!(task->flags & PF_EXITING))) {
  22                 hlist_add_head(&twork->hlist, &task->task_works);
  23                 err = 0;
  24         }
  25         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
  26
  27         /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
  28         if (likely(!err) && notify)
  29                 set_notify_resume(task);
  30         return err;
  31 }
  32
  33 struct task_work *
  34 task_work_cancel(struct task_struct *task, task_work_func_t func)
  35 {
  36         unsigned long flags;
  37         struct task_work *twork;
  38         struct hlist_node *pos;
  39
  40         raw_spin_lock_irqsave(&task->pi_lock, flags);
  41         hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
  42                 if (twork->func == func) {
  43                         hlist_del(&twork->hlist);
  44                         goto found;
  45                 }
  46         }
  47         twork = NULL;
  48  found:
  49         raw_spin_unlock_irqrestore(&task->pi_lock, flags);
  50
  51         return twork;
  52 }
  53
  54 void task_work_run(void)
  55 {
  56         struct task_struct *task = current;
  57         struct hlist_head task_works;
  58         struct hlist_node *pos;
  59
  60         raw_spin_lock_irq(&task->pi_lock);
  61         hlist_move_list(&task->task_works, &task_works);
  62         raw_spin_unlock_irq(&task->pi_lock);
  63
  64         if (unlikely(hlist_empty(&task_works)))
  65                 return;
  66         /*
  67          * We use hlist to save the space in task_struct, but we want fifo.
  68          * Find the last entry, the list should be short, then process them
  69          * in reverse order.
  70          */
  71         for (pos = task_works.first; pos->next; pos = pos->next)
  72                 ;
  73
  74         for (;;) {
  75                 struct hlist_node **pprev = pos->pprev;
  76                 struct task_work *twork = container_of(pos, struct task_work,
  77                                                         hlist);
  78                 twork->func(twork);
  79
  80                 if (pprev == &task_works.first)
  81                         break;
  82                 pos = container_of(pprev, struct hlist_node, next);
  83         }
  84 }