From: Peter Zijlstra <peterz@infradead.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: Markus Trippelsdorf <markus@trippelsdorf.de>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Torvald Riegel <triegel@redhat.com>
Subject: Re: commit cfafcd117 "futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()" causes glibc nptl/tst-robustpi8 failure
Date: Thu, 18 May 2017 08:57:23 +0200 [thread overview]
Message-ID: <20170518065723.iykfcoxvxj2clo5n@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170518064617.ujsw63hf2ycejgsz@hirez.programming.kicks-ass.net>
On Thu, May 18, 2017 at 08:46:17AM +0200, Peter Zijlstra wrote:
> On Wed, May 17, 2017 at 07:50:31PM +0200, Florian Weimer wrote:
> > On 05/17/2017 07:36 PM, Markus Trippelsdorf wrote:
> > > Since:
> > > commit cfafcd117da0216520568c195cb2f6cd1980c4bb
> > > Author: Peter Zijlstra <peterz@infradead.org>
> > > Date: Wed Mar 22 11:35:58 2017 +0100
> > >
> > > futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()
> > >
> > > glibc's nptl/tst-robustpi8 testcase fails:
> > >
> > > glibc-build % ./nptl/tst-robustpi8
> > > tst-robustpi8: ../nptl/pthread_mutex_lock.c:424: __pthread_mutex_lock_full: Assertion `INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust' failed.
> > >
> > > pthread_mutex_lock.c:
> > > 415 if (INTERNAL_SYSCALL_ERROR_P (e, __err)
> > > 416 && (INTERNAL_SYSCALL_ERRNO (e, __err) == ESRCH
> > > 417 || INTERNAL_SYSCALL_ERRNO (e, __err) == EDEADLK))
> > > 418 {
> > > 419 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != EDEADLK
> > > 420 || (kind != PTHREAD_MUTEX_ERRORCHECK_NP
> > > 421 && kind != PTHREAD_MUTEX_RECURSIVE_NP));
> > > 422 /* ESRCH can happen only for non-robust PI mutexes where
> > > 423 the owner of the lock died. */
> > > 424 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust);
> > >
> > > During bisection the commit above hangs the machine when I run the
> > > testcase.
> > >
> > > See: https://sourceware.org/bugzilla/show_bug.cgi?id=21487
> >
> > Markus, could you confirm that it is chocking on the EAGAIN failure? Or
> > is it something else?
> >
> > What is userspace supposed to do with the error code?
>
> IIRC that -EAGAIN should not get to userspace. The kernel should retry
> the lock operation. I'll go stare at it.
So commit:
bebe5b514345 ("futex: Futex_unlock_pi() determinism")
put a WARN_ON_ONCE() on that -EAGAIN condition, and since that doesn't
appear to be triggering, I suspect something else is buggered.
next prev parent reply other threads:[~2017-05-18 6:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-17 17:36 commit cfafcd117 "futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()" causes glibc nptl/tst-robustpi8 failure Markus Trippelsdorf
2017-05-17 17:50 ` Florian Weimer
2017-05-18 6:46 ` Peter Zijlstra
2017-05-18 6:57 ` Peter Zijlstra [this message]
2017-05-18 7:40 ` Peter Zijlstra
2017-05-18 8:04 ` Markus Trippelsdorf
2017-05-18 8:14 ` Peter Zijlstra
2017-05-18 8:12 ` Florian Weimer
2017-05-18 8:31 ` Peter Zijlstra
2017-05-18 8:34 ` Florian Weimer
2017-05-18 8:41 ` Peter Zijlstra
2017-05-18 8:42 ` Florian Weimer
2017-05-18 11:43 ` Peter Zijlstra
2017-05-18 12:30 ` Peter Zijlstra
2017-05-19 15:48 ` Peter Zijlstra
2017-05-19 16:07 ` Peter Zijlstra
2017-05-19 17:35 ` Markus Trippelsdorf
2017-05-22 20:04 ` [tip:locking/urgent] futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock() tip-bot for Peter Zijlstra
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