1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/spinlock.h>
3 #include <linux/task_work.h>
4 #include <linux/tracehook.h>
6 static struct callback_head work_exited
; /* all we need is ->next == NULL */
9 * task_work_add - ask the @task to execute @work->func()
10 * @task: the task which should run the callback
11 * @work: the callback to run
12 * @notify: how to notify the targeted task
14 * Queue @work for task_work_run() below and notify the @task if @notify
15 * is @TWA_RESUME or @TWA_SIGNAL. @TWA_SIGNAL works like signals, in that the
16 * it will interrupt the targeted task and run the task_work. @TWA_RESUME
17 * work is run only when the task exits the kernel and returns to user mode,
18 * or before entering guest mode. Fails if the @task is exiting/exited and thus
19 * it can't process this @work. Otherwise @work->func() will be called when the
20 * @task goes through one of the aforementioned transitions, or exits.
22 * If the targeted task is exiting, then an error is returned and the work item
23 * is not queued. It's up to the caller to arrange for an alternative mechanism
26 * Note: there is no ordering guarantee on works queued here. The task_work
30 * 0 if succeeds or -ESRCH.
32 int task_work_add(struct task_struct
*task
, struct callback_head
*work
,
33 enum task_work_notify_mode notify
)
35 struct callback_head
*head
;
38 head
= READ_ONCE(task
->task_works
);
39 if (unlikely(head
== &work_exited
))
42 } while (cmpxchg(&task
->task_works
, head
, work
) != head
);
48 set_notify_resume(task
);
51 set_notify_signal(task
);
60 EXPORT_SYMBOL(task_work_add
);
63 * task_work_cancel - cancel a pending work added by task_work_add()
64 * @task: the task which should execute the work
65 * @func: identifies the work to remove
67 * Find the last queued pending work with ->func == @func and remove
71 * The found work or NULL if not found.
73 struct callback_head
*
74 task_work_cancel(struct task_struct
*task
, task_work_func_t func
)
76 struct callback_head
**pprev
= &task
->task_works
;
77 struct callback_head
*work
;
80 if (likely(!task
->task_works
))
83 * If cmpxchg() fails we continue without updating pprev.
84 * Either we raced with task_work_add() which added the
85 * new entry before this work, we will find it again. Or
86 * we raced with task_work_run(), *pprev == NULL/exited.
88 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
89 while ((work
= READ_ONCE(*pprev
))) {
90 if (work
->func
!= func
)
92 else if (cmpxchg(pprev
, work
, work
->next
) == work
)
95 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
101 * task_work_run - execute the works added by task_work_add()
103 * Flush the pending works. Should be used by the core kernel code.
104 * Called before the task returns to the user-mode or stops, or when
105 * it exits. In the latter case task_work_add() can no longer add the
106 * new work after task_work_run() returns.
108 void task_work_run(void)
110 struct task_struct
*task
= current
;
111 struct callback_head
*work
, *head
, *next
;
115 * work->func() can do task_work_add(), do not set
116 * work_exited unless the list is empty.
120 work
= READ_ONCE(task
->task_works
);
122 if (task
->flags
& PF_EXITING
)
127 } while (cmpxchg(&task
->task_works
, work
, head
) != work
);
132 * Synchronize with task_work_cancel(). It can not remove
133 * the first entry == work, cmpxchg(task_works) must fail.
134 * But it can remove another entry from the ->next list.
136 raw_spin_lock_irq(&task
->pi_lock
);
137 raw_spin_unlock_irq(&task
->pi_lock
);
147 EXPORT_SYMBOL_GPL(task_work_run
);