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Message-ID: <161c2e25-3d26-4dd7-d378-d1741f7bcca8@redhat.com>
Date:   Mon, 11 Apr 2022 17:07:38 -0400
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Subject: Re: [PATCH v5] locking/rwsem: Make handoff bit handling more
 consistent
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To:     john.p.donnelly@oracle.com,
        chenguanyou <chenguanyou9338@gmail.com>,
        gregkh@linuxfoundation.org
Cc:     dave@stgolabs.net, hdanton@sina.com, linux-kernel@vger.kernel.org,
        mazhenhua@xiaomi.com, mingo@redhat.com, peterz@infradead.org,
        quic_aiquny@quicinc.com, will@kernel.org, sashal@kernel.org
References: <20211116012912.723980-1-longman@redhat.com>
 <20220214154741.12399-1-chenguanyou@xiaomi.com>
 <3f02975c-1a9d-be20-32cf-f1d8e3dfafcc@oracle.com>
 <e873727e-22db-3330-015d-bd6581a2937a@redhat.com>
 <31178c33-e25c-c3e8-35e2-776b5211200c@oracle.com>
From:   Waiman Long <longman@redhat.com>
In-Reply-To: <31178c33-e25c-c3e8-35e2-776b5211200c@oracle.com>
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On 4/11/22 17:03, john.p.donnelly@oracle.com wrote:
>
>>>
>>> I have reached out to Waiman and he suggested this for our next test 
>>> pass:
>>>
>>>
>>> 1ee326196c6658 locking/rwsem: Always try to wake waiters in 
>>> out_nolock path
>>
>> Does this commit help to avoid the lockup problem?
>>
>> Commit 1ee326196c6658 fixes a potential missed wakeup problem when a 
>> reader first in the wait queue is interrupted out without acquiring 
>> the lock. It is actually not a fix for commit d257cc8cb8d5. However, 
>> this commit changes the out_nolock path behavior of writers by 
>> leaving the handoff bit set when the wait queue isn't empty. That 
>> likely makes the missed wakeup problem easier to reproduce.
>>
>> Cheers,
>> Longman
>>
>
> Hi,
>
>
> We are testing now
>
> ETA for fio soak test completion is  ~15hr from now.
>
> I wanted to share the stack traces for future reference + occurrences.
>
I am looking forward to your testing results tomorrow.

Cheers,
Longman