References: <20171129175605.GA863@jcartwri.amer.corp.natinst.com> <20171206234622.GZ3326@worktop>
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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
In-reply-to: <20171206234622.GZ3326@worktop>
Date: Wed, 06 Dec 2017 20:09:28 -0600
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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