linux-kernel - Re: Lockups due to "locking/rwsem: Make handoff bit handling more consistent"

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Message-ID: <2c4084e3-9bd0-76ef-a11c-857de96a83e5@redhat.com>
Date:   Tue, 21 Jun 2022 21:32:12 -0400
From:   Waiman Long <longman@...hat.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Zhenhua Ma <mazhenhua@...omi.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: Lockups due to "locking/rwsem: Make handoff bit handling more
 consistent"

On 6/20/22 10:09, Mel Gorman wrote:
> On Fri, Jun 17, 2022 at 10:29:20AM -0400, Waiman Long wrote:
>>> The C file and shell script to run it are attached.
>>>
>> Thanks for the reproducer and I will try to reproduce it locally.
>>
>> It is a known issue that I have receive similar report from an Oracle
>> engineer. That is the reason I posted commit 1ee326196c66 ("locking/rwsem:
>> Always try to wake waiters in out_nolock path") that was merged in v5.19. I
>> believe it helps but it may not be able to eliminate all possible race
>> conditions. To make rwsem behave more like before commit d257cc8cb8d5
>> ("locking/rwsem: Make handoff bit handling more consistent"), I posted a
>> follow-up patch
>>
>> https://lore.kernel.org/lkml/20220427173124.1428050-1-longman@redhat.com/
>>
>> But it hasn't gotten review yet.
>>
> FWIW, the patch passed the test case when applied to both 5.18 and
> 5.19-rc3.

Thanks for running the test. Do you mean that both 5.18 and 5.19-rc3 
fail the test and they pass only after applying the patch?

Anyway, I am not able to reproduce the failure in both 5.18 and 
5.19-rc3. Perhaps it is due to the difference in the running 
environment, i.e. gcc, glibc, etc. What operating environment (SuSE 
version) do you use to reproduce the failure? I used RHEL8 which is the 
most convenient one for me.

BTW, do you mind if I put down your name with a "Tested-by:" tag to the 
patch?

Thanks,
Longman