task_work: teach task_work_add() to do signal_wake_up()
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>
diff --git a/kernel/signal.c b/kernel/signal.c
index 5ca48cc..ee22ec7 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2529,9 +2529,6 @@ bool get_signal(struct ksignal *ksig)
struct signal_struct *signal = current->signal;
int signr;
- if (unlikely(current->task_works))
- task_work_run();
-
if (unlikely(uprobe_deny_signal()))
return false;
@@ -2544,6 +2541,13 @@ bool get_signal(struct ksignal *ksig)
relock:
spin_lock_irq(&sighand->siglock);
+ current->jobctl &= ~JOBCTL_TASK_WORK;
+ if (unlikely(current->task_works)) {
+ spin_unlock_irq(&sighand->siglock);
+ task_work_run();
+ goto relock;
+ }
+
/*
* Every stopped thread goes here after wakeup. Check to see if
* we should notify the parent, prepare_signal(SIGCONT) encodes