linux-kernel - Re: [patch v6.1 17/20] signal: Queue ignored posixtimers on ignore list

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Message-ID: <87plnbowh6.ffs@tglx>
Date: Mon, 04 Nov 2024 16:21:57 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Anna-Maria Behnsen
 <anna-maria@...utronix.de>, John Stultz <jstultz@...gle.com>, Peter
 Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Stephen
 Boyd <sboyd@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, Oleg
 Nesterov <oleg@...hat.com>
Subject: Re: [patch v6.1 17/20] signal: Queue ignored posixtimers on ignore
 list

On Mon, Nov 04 2024 at 12:42, Frederic Weisbecker wrote:
> But there is something more problematic against the delete() path:
>                                    
> Thread within                  Signal target             Timer target
> signal target group
> --------------------           -------------             -------------
>                                                          timr->it_status = POSIX_TIMER_REQUEUE_PENDING
>                                                          posixtimer_send_sigqueue();
>                                                          do_exit();
> timer_delete()
>     posix_cpu_timer_del()
>         // return NULL
>         cpu_timer_task_rcu()
>         // timer->it_status NOT set
>         // to POSIX_TIMER_DISARMED
>     hlist_del(&timer->list);
>     posix_timer_cleanup_ignored()
>
>
>                                do_sigaction(SIG_IGN...)
>                                flush_sigqueue_mask()
>                                   sigqueue_free_ignored()
>                                       posixtimer_sig_ignore()
>                                           // Observe POSIX_TIMER_REQUEUE_PENDING
>                                           hlist_add_head(...ignored_posix_timers)
>                                do_exit()
>                                    exit_itimers()
>                                    if (hlist_empty(&tsk->signal->posix_timers))
>                                        return;
>                                    // leaked timer queued to migrate list
>                                    

Duh. Let me stare at that some more.