Re: posix timer freeze after some random time, under pthread create/destroy load

[Oleg Nesterov <oleg@redhat.com>]

On 11/21, Frederic Weisbecker wrote:
>
> I think this started with commit:
>
> bcb7ee79029d (posix-timers: Prefer delivery of signals to the current thread)
>
> The problem is that if the current task is exiting and has already been reaped,
> its sighand pointer isn't there anymore.

Thanks...

This can only happen if the exiting task has already passed exit_notify() which
sets exit_state. So I'd suggest to check current->exit_state instead of PF_EXITING
in the patch below.

Oleg.

> And so the signal is ignored even
> though it should be queued to and handled by the thread group that has other
> live threads to take care of it.
>
> Can you test the following patch? I'm cooking another patch with changelog for
> upstream that has seen recent changes in this area.
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 8f6330f0e9ca..4cadee618d4b 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1984,7 +1984,8 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
>  	t = pid_task(pid, type);
>  	if (!t)
>  		goto ret;
> -	if (type != PIDTYPE_PID && same_thread_group(t, current))
> +	if (type != PIDTYPE_PID && same_thread_group(t, current) &&
> +	    !(current->flags & PF_EXITING))
>  		t = current;
>  	if (!likely(lock_task_sighand(t, &flags)))
>  		goto ret;
>
>