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

[Oleg Nesterov <oleg@redhat.com>]

On 11/22, Frederic Weisbecker wrote:
>
> Le Fri, Nov 22, 2024 at 09:24:07AM +0100, Oleg Nesterov a écrit :
> > 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.
>
> Right, I don't mind either way,

Me too, so feel free to ignore,

> though if it's past PF_EXITING,
> complete_signal() -> wants_signal() will defer to another thread anyway, right?

Right. So I think it would be better to rely on complete_signal() in this
case even if the current logic is very simple and dumb.

> Due to retarget_shared_pending() being called after the flag being set...

Yes. Whatever we do send_sigqueue/complete_signal can choose an exiting thread
which doesn't have PF_EXITING yet, in this case retarget_shared_pending() from
that thread will pick another target for signal_wake_up/TIF_SIGPENDING.

Thanks!

Oleg.