linux-kernel - Re: WARN_ON_ONCE(!new_owner) within wake_futex

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Message-ID: <20190129093327.GE28485@hirez.programming.kicks-ass.net>
Date:   Tue, 29 Jan 2019 10:33:27 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-s390@...r.kernel.org,
        Stefan Liebler <stli@...ux.ibm.com>,
        Sebastian Sewior <bigeasy@...utronix.de>
Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered

On Tue, Jan 29, 2019 at 10:01:08AM +0100, Heiko Carstens wrote:

> However now I see every now and then the following failure from the
> same test case:
> 
> tst-robustpi8: ../nptl/pthread_mutex_lock.c:425: __pthread_mutex_lock_full: Assertion `INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust' failed.
> 
> 		/* ESRCH can happen only for non-robust PI mutexes where
> 		   the owner of the lock died.	*/
> 		assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust);
> 
> I just verified that this happened also without your patch, I just
> didn't see it since I started my tests with panic_on_warn=1 and the
> warning triggered always earlier.
> So, this seems to be something different.

*groan*... so while the other thing reproduced, I've not seen this
happen and I ran the test for hours.

I'll start it up again, see what happens..