Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <b3620b7b-c66a-65f8-b10b-c3669b2f82ec@redhat.com>
Date:   Tue, 12 Apr 2022 13:04:05 -0400
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH v5] locking/rwsem: Make handoff bit handling more
 consistent
Content-Language: en-US
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,
        stable@vger.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>
 <161c2e25-3d26-4dd7-d378-d1741f7bcca8@redhat.com>
 <2b6ed542-b3e0-1a87-33ac-d52fc0e0339c@oracle.com>
From:   Waiman Long <longman@redhat.com>
In-Reply-To: <2b6ed542-b3e0-1a87-33ac-d52fc0e0339c@oracle.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 4/12/22 12:28, john.p.donnelly@oracle.com wrote:
> On 4/11/22 4:07 PM, Waiman Long wrote:
>>
>> 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
>>
> Hi
>
>  Our 24hr fio soak test with :
>
>  1ee326196c6658 locking/rwsem: Always try to wake waiters in 
> out_nolock path
>
>
>  applied to 5.15.30  passed.
>
>  I suggest you append  1ee326196c6658 with :
>
>
>  cc: stable
>
>   Fixes: d257cc8cb8d5 ("locking/rwsem: Make handoff bit handling more 
> consistent")
>
>
> I'll leave the implementation details up to the core maintainers how 
> to do that ;-)

Thanks for the test.

The patch has already been in the tip tree. It may not be easy to add a 
Fixes tag to it. Anyway, I will encourage stable tree maintainer to take 
it as it does fix a problem as shown in your test.

Cheers,
Longman