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task_work: teach task_work_add() to do signal_wake_up()

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So that the target task will exit the wait_event_interruptible-like
loop and call task_work_run() asap.

The patch turns "bool notify" into 0,TWA_RESUME,TWA_SIGNAL enum, the
new TWA_SIGNAL flag implies signal_wake_up().  However, it needs to
avoid the race with recalc_sigpending(), so the patch also adds the
new JOBCTL_TASK_WORK bit included in JOBCTL_PENDING_MASK.

TODO: once this patch is merged we need to change all current users
of task_work_add(notify = true) to use TWA_RESUME.

Cc: stable@vger.kernel.org # v5.7
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Oleg Nesterov
2020-06-30 17:32:54 +02:00
committed by Jens Axboe
parent d60b5fbc1c
commit e91b481623
4 changed files with 28 additions and 7 deletions
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16
kernel/task_work.c
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@@ -25,9 +25,10 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
* 0 if succeeds or -ESRCH.
*/
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
task_work_add(struct task_struct *task, struct callback_head *work, int notify)
{
struct callback_head *head;
unsigned long flags;
do {
head = READ_ONCE(task->task_works);
@@ -36,8 +37,19 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
work->next = head;
} while (cmpxchg(&task->task_works, head, work) != head);
if (notify)
switch (notify) {
case TWA_RESUME:
set_notify_resume(task);
break;
case TWA_SIGNAL:
if (lock_task_sighand(task, &flags)) {
task->jobctl |= JOBCTL_TASK_WORK;
signal_wake_up(task, 0);
unlock_task_sighand(task, &flags);
}
break;
}
return 0;
}