linux/kernel/task_work.c
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   1#include <linux/spinlock.h>
   2#include <linux/task_work.h>
   3#include <linux/tracehook.h>
   4
   5int
   6task_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
  33struct task_work *
  34task_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
  54void 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}
  85
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