Root/kernel/task_work.c

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

Archive Download this file



interactive