Re: commit 894d1b3db41c leads to frequent hangs when booting

[Bert Karwatzki <spasswolf@web.de>]

Am Mittwoch, dem 11.12.2024 um 15:14 -0800 schrieb John Stultz:
> On Wed, Dec 11, 2024 at 2:46 PM Bert Karwatzki <spasswolf@web.de> wrote:
> >
> > Am Mittwoch, dem 11.12.2024 um 22:35 +0100 schrieb Bert Karwatzki:
> > > I have confirmed that I that linux-next-20241210 is fixed by the same revert
> > > as v6.13-rc2 (ten boots without incident is the criterion for a good commit)
> > >
> > >
> > > Bert Karwatzki
> >
> > Also this bug only occurs with CONFIG_PREEMPT_RT=y, I've just checked v6.13-rc2
> > without the revert and the following preempt settings and got 10 clean boots:
> >
>
> Hrm. That matches the case where the fix here helped:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=82f9cc094975240885c93effbca7f4603f5de1bf
>
>
> I'm still working on getting a minimal delta from your config booting
> in my environment, but in the meantime, I'd be curious if the
> following reduced revert helps?
>   https://github.com/johnstultz-work/linux-dev/commit/60c60f85670fb1f4708adbe55e15ab918d96f9f0
>
> Basically just trying to clarify if the problem is moving the wakeup
> to the wake_q or if some other interaction (maybe with the
> preempt_disables) could be causing the issue.
> (I'm assuming you have 82f9cc094975 applied when you test with that change)
>
> thanks
> -john

I tested linux-next-20241210 (which includes 82f9cc094975) with your patch

diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
index 37f025a096c9..724d4c871cf6 100644
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -284,7 +284,7 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER
*waiter,
 #ifndef WW_RT
                debug_mutex_wake_waiter(lock, waiter);
 #endif
-               wake_q_add(wake_q, waiter->task);
+               wake_up_process(waiter->task);
        }

        return true;
@@ -332,7 +332,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
                 * wakeup pending to re-read the wounded state.
                 */
                if (owner != current)
-                       wake_q_add(wake_q, owner);
+                       wake_up_process(owner);

                return true;
        }

and this fixes the issue for me.

Bert Karwatzki