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From:   Florian Weimer <fweimer@redhat.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Darren Hart <darren@dvhart.com>,
        Yi Wang <wang.yi59@zte.com.cn>,
        Yang Tao <yang.tao172@zte.com.cn>,
        Oleg Nesterov <oleg@redhat.com>,
        Carlos O'Donell <carlos@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [patch 00/12] futex: Cure robust/PI futex exit races
References: <20191106215534.241796846@linutronix.de>
        <87zhh78gnf.fsf@oldenburg2.str.redhat.com>
        <87v9rv8g44.fsf@oldenburg2.str.redhat.com>
Date:   Fri, 08 Nov 2019 08:38:46 +0100
In-Reply-To: <87v9rv8g44.fsf@oldenburg2.str.redhat.com> (Florian Weimer's
        message of "Thu, 07 Nov 2019 23:40:43 +0100")
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* Florian Weimer:

> * Florian Weimer:
>
>> * Thomas Gleixner:
>>
>>> The series is also available from git:
>>>
>>>   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.locking=
/futex
>>
>> I ran the glibc upstream test suite (which has some robust futex tests)
>> against b21be7e942b49168ee15a75cbc49fbfdeb1e6a97 on x86-64, both native
>> and 32-bit/i386 compat mode.
>>
>> compat mode seems broken, nptl/tst-thread-affinity-pthread fails.  This
>> is probably *not* due to
>> <https://bugzilla.kernel.org/show_bug.cgi?id=3D154011> because the failu=
re
>> is non-sporadic, but reliable fails for thread 253:
>>
>> info: Detected CPU set size (in bits): 225
>> info: Maximum test CPU: 255
>> error: pthread_create for thread 253 failed: Resource temporarily unavai=
lable
>>
>> I'm running this on a large box as root, so ulimits etc. do not apply.
>>
>> I did not see this failure with the x86-64 test.
>>
>> You should be able to reproduce with (assuming you've got a multilib gcc=
):
>>
>> git clone git://sourceware.org/git/glibc.git git
>> mkdir build
>> cd build
>> ../git/configure --prefix=3D/usr CC=3D"gcc -m32" CXX=3D"g++ -m32" --buil=
d=3Di686-linux
>> make -j`nproc`
>> make test t=3Dnptl/tst-thread-affinity-pthread
>
> Sorry, I realized that I didn't actually verify that this is a
> regression caused by your patches.  Maybe I can do that tomorrow.

Confirmed as a regression caused by the patches.  Depending on the
nature of the bug, you need a machine which has or pretends to have many
CPUs (this one has 256 CPUs).

Please let me know if you need more information.

Thanks,
Florian