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From: Gratian Crisan <gratian.crisan@ni.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Julia Cartwright <julia@ni.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Gratian Crisan <gratian.crisan@ni.com>,
	linux-kernel@vger.kernel.org, Darren Hart <dvhart@infradead.org>,
	Ingo Molnar <mingo@redhat.com>
Subject: Re: PI futexes + lock stealing woes
Date: Wed, 06 Dec 2017 20:09:28 -0600	[thread overview]
Message-ID: <87y3mf8f1j.fsf@ni.com> (raw)
In-Reply-To: <20171206234622.GZ3326@worktop>


Peter Zijlstra writes:

> On Wed, Nov 29, 2017 at 11:56:05AM -0600, Julia Cartwright wrote:
>
>> fixup_owner() used to have additional seemingly relevant checks in place
>> that were removed 73d786bd043eb ("futex: Rework inconsistent
>> rt_mutex/futex_q state").
>
> *groan*... yes. I completely missed that extra case also applied to
> requeue_pi (requeue always did hurt my brain).

FWIW I have been testing for about two days now with the fixup_owner()
hunk of 73d786bd043eb ("futex: Rework inconsistent rt_mutex/futex_q
state") reverted. So far it hasn't hit the race/deadlock. It normally
takes around 8 hours to reproduce.

I've also tried Julia's msleep() trick for expanding the race window for
the last 4 hours or so of testing and it seems to be still going.

Thanks,
    Gratian

  reply	other threads:[~2017-12-07  2:17 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-29 17:56 PI futexes + lock stealing woes Julia Cartwright
2017-12-01 20:11 ` Darren Hart
2017-12-01 21:49   ` Julia Cartwright
2017-12-02  0:32     ` Darren Hart
2017-12-06 23:46 ` Peter Zijlstra
2017-12-07  2:09   ` Gratian Crisan [this message]
2017-12-07 10:45     ` Peter Zijlstra
2017-12-07 14:26       ` Peter Zijlstra
2017-12-07 14:57         ` Gratian Crisan
2017-12-07 19:50           ` Julia Cartwright
2017-12-07 23:02             ` Gratian Crisan
2017-12-08 12:49               ` [PATCH] futex: Avoid violating the 10th rule of futex Peter Zijlstra
2017-12-08 16:04                 ` Gratian Crisan
2018-01-08 21:09                 ` Julia Cartwright
2018-01-14 18:06                 ` [tip:locking/urgent] " tip-bot for Peter Zijlstra

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