linux-kernel - Re: [patch 00/12] futex: Cure robust/PI futex exit races

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Date:   Fri, 8 Nov 2019 11:37:58 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Florian Weimer <fweimer@...hat.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Darren Hart <darren@...art.com>,
        Yi Wang <wang.yi59@....com.cn>,
        Yang Tao <yang.tao172@....com.cn>,
        Oleg Nesterov <oleg@...hat.com>,
        Carlos O'Donell <carlos@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [patch 00/12] futex: Cure robust/PI futex exit races

On Fri, 8 Nov 2019, Florian Weimer wrote:
> > On Fri, 8 Nov 2019, Florian Weimer wrote:
> > Unpatched 5.4-rc6:
> >
> > FAIL: nptl/tst-thread-affinity-pthread
> > original exit status 1
> > info: Detected CPU set size (in bits): 225
> > info: Maximum test CPU: 255
> > error: pthread_create for thread 253 failed: Resource temporarily unavailable
> 
> Huh.  Reverting your patches (at commit 26bc672134241a080a83b2ab9aa8abede8d30e1c)
> fixes the test for me.
> 
> > TBH, the futex changes have absolutely nothing to do with that resource
> > fail.
> 
> I suspect that there are some changes to task exit latency, which
> triggers the latent resource management bug.

Right, and depending on which hardware you run, this changes. On the big
testbox I use the failure is also bouncing around between thread 252 and
254.

Thanks,

	tglx