linux-ext4 - Re: [PATCH 02/12] locking/rwsem: Exit early when held by an anonymous owner

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Date:   Tue, 14 Jan 2020 13:33:33 -0500
From:   Waiman Long <longman@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-ext4@...r.kernel.org, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 02/12] locking/rwsem: Exit early when held by an anonymous
 owner

On 1/14/20 1:25 PM, Christoph Hellwig wrote:
> On Tue, Jan 14, 2020 at 01:17:45PM -0500, Waiman Long wrote:
>> The owner field is just a pointer to the task structure with the lower 3
>> bits served as flag bits. Setting owner to RWSEM_OWNER_UNKNOWN (-2) will
>> stop optimistic spinning. So under what condition did the crash happen?
> When running xfstests with all patches in this series except for this
> one, IIRC in generic/114.

OK, I think I know where the bug is. I will send a patch to fix that.

Thanks,
Longman