From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Sewior <bigeasy@linutronix.de>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-s390@vger.kernel.org, Stefan Liebler <stli@linux.ibm.com>
Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggerede
Date: Wed, 30 Jan 2019 17:44:42 -0800 [thread overview]
Message-ID: <20190131014442.GB4240@linux.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1901310049440.8200@nanos.tec.linutronix.de>
On Thu, Jan 31, 2019 at 12:55:18AM +0100, Thomas Gleixner wrote:
> On Wed, 30 Jan 2019, Paul E. McKenney wrote:
> > On Thu, Jan 31, 2019 at 12:13:51AM +0100, Thomas Gleixner wrote:
> > > I might be wrong as usual, but this would definitely explain the fail very
> > > well.
> >
> > On recent versions of GCC, the fix would be to put this between the two
> > stores that need ordering:
> >
> > __atomic_thread_fence(__ATOMIC_RELEASE);
> >
> > I must defer to Heiko on whether s390 GCC might tear the stores. My
> > guess is "probably not". ;-)
>
> So I just checked the latest glibc code. It has:
>
> /* We must not enqueue the mutex before we have acquired it.
> Also see comments at ENQUEUE_MUTEX. */
> __asm ("" ::: "memory");
> ENQUEUE_MUTEX_PI (mutex);
> /* We need to clear op_pending after we enqueue the mutex. */
> __asm ("" ::: "memory");
> THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
>
> 8f9450a0b7a9 ("Add compiler barriers around modifications of the robust mutex list.")
>
> in the glibc repository, There since Dec 24 2016 ...
>
> So the question is whether this is sufficient. That ordering only only
> matters vs. the thread itself and not for others.
Ah, in that case you can use __atomic_signal_fence(__ATOMIC_RELEASE)
instead of the __atomic_thread_fence(__ATOMIC_RELEASE).
The __atomic_thread_fence(__ATOMIC_RELEASE) provides ordering between
threads, but __atomic_signal_fence(__ATOMIC_RELEASE) only does so
within a thread.
Thanx, Paul
next prev parent reply other threads:[~2019-01-31 1:44 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 8:11 WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Heiko Carstens
2018-11-28 14:32 ` Thomas Gleixner
2018-11-29 11:23 ` Heiko Carstens
2019-01-21 12:21 ` Heiko Carstens
2019-01-21 13:12 ` Thomas Gleixner
2019-01-22 21:14 ` Thomas Gleixner
2019-01-23 9:24 ` Heiko Carstens
2019-01-23 12:33 ` Thomas Gleixner
2019-01-23 12:40 ` Heiko Carstens
2019-01-28 13:44 ` Peter Zijlstra
2019-01-28 13:58 ` Peter Zijlstra
2019-01-28 15:53 ` Thomas Gleixner
2019-01-29 8:49 ` Peter Zijlstra
2019-01-29 22:15 ` [PATCH] futex: Handle early deadlock return correctly Thomas Gleixner
2019-01-30 12:01 ` Thomas Gleixner
2019-02-08 12:05 ` [tip:locking/urgent] " tip-bot for Thomas Gleixner
2019-01-29 9:01 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Heiko Carstens
2019-01-29 9:33 ` Peter Zijlstra
2019-01-29 9:45 ` Thomas Gleixner
2019-01-29 10:24 ` Heiko Carstens
2019-01-29 10:35 ` Peter Zijlstra
2019-01-29 13:03 ` Thomas Gleixner
2019-01-29 13:23 ` Heiko Carstens
[not found] ` <20190129151058.GG26906@osiris>
2019-01-29 17:16 ` Sebastian Sewior
2019-01-29 21:45 ` Thomas Gleixner
[not found] ` <20190130094913.GC5299@osiris>
2019-01-30 12:15 ` Thomas Gleixner
[not found] ` <20190130125955.GD5299@osiris>
2019-01-30 13:24 ` Sebastian Sewior
2019-01-30 13:29 ` Thomas Gleixner
2019-01-30 14:33 ` Thomas Gleixner
2019-01-30 17:56 ` Thomas Gleixner
2019-01-30 21:07 ` Sebastian Sewior
2019-01-30 23:13 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggerede Thomas Gleixner
2019-01-30 23:35 ` Paul E. McKenney
2019-01-30 23:55 ` Thomas Gleixner
2019-01-31 0:27 ` Thomas Gleixner
2019-01-31 1:45 ` Paul E. McKenney
2019-01-31 16:52 ` Heiko Carstens
2019-01-31 17:06 ` Sebastian Sewior
2019-01-31 20:42 ` Heiko Carstens
2019-02-01 16:12 ` Heiko Carstens
2019-02-01 21:59 ` Thomas Gleixner
[not found] ` <20190202091043.GA3381@osiris>
2019-02-02 10:14 ` Thomas Gleixner
2019-02-02 11:20 ` Heiko Carstens
2019-02-03 16:30 ` Thomas Gleixner
2019-02-04 11:40 ` Heiko Carstens
2019-01-31 1:44 ` Paul E. McKenney [this message]
2019-01-30 13:25 ` WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered Thomas Gleixner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190131014442.GB4240@linux.ibm.com \
--to=paulmck@linux.ibm.com \
--cc=bigeasy@linutronix.de \
--cc=heiko.carstens@de.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=schwidefsky@de.ibm.com \
--cc=stli@linux.ibm.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).