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Subject[PATCH] pidfd: Add warning if exit_state is 0 during notification
Date
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.

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

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
kernel/signal.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/signal.c b/kernel/signal.c
index 91b789dd6e72..349f5a67f100 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -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);
}
--
2.22.0.657.g960e92d24f-goog
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