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pidfd: Add warning if exit_state is 0 during notification

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Previously a condition got missed where the pidfd waiters are awakened
before the exit_state gets set. This can result in a missed notification
[1] and the polling thread waiting forever.

It is fixed now, however it would be nice to avoid this kind of issue
going unnoticed in the future. So just add a warning to catch it in the
future.

/* References */
[1]: https://lore.kernel.org/lkml/20190717172100.261204-1-joel@joelfernandes.org/

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20190724164816.201099-1-joel@joelfernandes.org
Signed-off-by: Christian Brauner <christian@brauner.io>
This commit is contained in:
Joel Fernandes (Google) 2019-07-24 12:48:16 -04:00 committed by Christian Brauner
parent 3884ae44f4
commit 1caf7d50f4
1 changed files with 1 additions and 0 deletions
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kernel/signal.c
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@ -1885,6 +1885,7 @@ static void do_notify_pidfd(struct task_struct *task)
{
struct pid *pid;
WARN_ON(task->exit_state == 0);
pid = task_pid(task);
wake_up_all(&pid->wait_pidfd);
}