1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/spinlock.h>
3 #include <linux/task_work.h>
4 #include <linux/resume_user_mode.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, @TWA_SIGNAL, or @TWA_SIGNAL_NO_IPI.
17 * @TWA_SIGNAL works like signals, in that the it will interrupt the targeted
18 * task and run the task_work, regardless of whether the task is currently
19 * running in the kernel or userspace.
20 * @TWA_SIGNAL_NO_IPI works like @TWA_SIGNAL, except it doesn't send a
21 * reschedule IPI to force the targeted task to reschedule and run task_work.
22 * This can be advantageous if there's no strict requirement that the
23 * task_work be run as soon as possible, just whenever the task enters the
25 * @TWA_RESUME work is run only when the task exits the kernel and returns to
26 * user mode, or before entering guest mode.
28 * Fails if the @task is exiting/exited and thus it can't process this @work.
29 * Otherwise @work->func() will be called when the @task goes through one of
30 * the aforementioned transitions, or exits.
32 * If the targeted task is exiting, then an error is returned and the work item
33 * is not queued. It's up to the caller to arrange for an alternative mechanism
36 * Note: there is no ordering guarantee on works queued here. The task_work
40 * 0 if succeeds or -ESRCH.
42 int task_work_add(struct task_struct
*task
, struct callback_head
*work
,
43 enum task_work_notify_mode notify
)
45 struct callback_head
*head
;
47 /* record the work call stack in order to print it in KASAN reports */
48 kasan_record_aux_stack(work
);
50 head
= READ_ONCE(task
->task_works
);
52 if (unlikely(head
== &work_exited
))
55 } while (!try_cmpxchg(&task
->task_works
, &head
, work
));
61 set_notify_resume(task
);
64 set_notify_signal(task
);
66 case TWA_SIGNAL_NO_IPI
:
67 __set_notify_signal(task
);
78 * task_work_cancel_match - cancel a pending work added by task_work_add()
79 * @task: the task which should execute the work
80 * @match: match function to call
81 * @data: data to be passed in to match function
84 * The found work or NULL if not found.
86 struct callback_head
*
87 task_work_cancel_match(struct task_struct
*task
,
88 bool (*match
)(struct callback_head
*, void *data
),
91 struct callback_head
**pprev
= &task
->task_works
;
92 struct callback_head
*work
;
95 if (likely(!task_work_pending(task
)))
98 * If cmpxchg() fails we continue without updating pprev.
99 * Either we raced with task_work_add() which added the
100 * new entry before this work, we will find it again. Or
101 * we raced with task_work_run(), *pprev == NULL/exited.
103 raw_spin_lock_irqsave(&task
->pi_lock
, flags
);
104 work
= READ_ONCE(*pprev
);
106 if (!match(work
, data
)) {
108 work
= READ_ONCE(*pprev
);
109 } else if (try_cmpxchg(pprev
, &work
, work
->next
))
112 raw_spin_unlock_irqrestore(&task
->pi_lock
, flags
);
117 static bool task_work_func_match(struct callback_head
*cb
, void *data
)
119 return cb
->func
== data
;
123 * task_work_cancel - cancel a pending work added by task_work_add()
124 * @task: the task which should execute the work
125 * @func: identifies the work to remove
127 * Find the last queued pending work with ->func == @func and remove
131 * The found work or NULL if not found.
133 struct callback_head
*
134 task_work_cancel(struct task_struct
*task
, task_work_func_t func
)
136 return task_work_cancel_match(task
, task_work_func_match
, func
);
140 * task_work_run - execute the works added by task_work_add()
142 * Flush the pending works. Should be used by the core kernel code.
143 * Called before the task returns to the user-mode or stops, or when
144 * it exits. In the latter case task_work_add() can no longer add the
145 * new work after task_work_run() returns.
147 void task_work_run(void)
149 struct task_struct
*task
= current
;
150 struct callback_head
*work
, *head
, *next
;
154 * work->func() can do task_work_add(), do not set
155 * work_exited unless the list is empty.
157 work
= READ_ONCE(task
->task_works
);
161 if (task
->flags
& PF_EXITING
)
166 } while (!try_cmpxchg(&task
->task_works
, &work
, head
));
171 * Synchronize with task_work_cancel(). It can not remove
172 * the first entry == work, cmpxchg(task_works) must fail.
173 * But it can remove another entry from the ->next list.
175 raw_spin_lock_irq(&task
->pi_lock
);
176 raw_spin_unlock_irq(&task
->pi_lock
);