linux-kernel - Re: [PATCH v5 3/3] rseq/selftests: Add test for mm

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Message-ID: <60671af0-204d-413e-9b65-00b526764ab9@linuxfoundation.org>
Date: Tue, 18 Feb 2025 16:45:58 -0700
From: Shuah Khan <skhan@...uxfoundation.org>
To: Gabriele Monaco <gmonaco@...hat.com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
 "Paul E. McKenney" <paulmck@...nel.org>, Shuah Khan <shuah@...nel.org>,
 Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v5 3/3] rseq/selftests: Add test for mm_cid compaction

On 2/10/25 08:25, Gabriele Monaco wrote:
> 
> 
> On Mon, 2025-02-10 at 15:53 +0100, Mathieu Desnoyers wrote:
>> On 2025-02-10 08:57, Gabriele Monaco wrote:
>>> A task in the kernel (task_mm_cid_work) runs somewhat periodically
>>> to
>>> compact the mm_cid for each process. Add a test to validate that it
>>> runs
>>> correctly and timely.
>>>
>>> The test spawns 1 thread pinned to each CPU, then each thread,
>>> including
>>> the main one, runs in short bursts for some time. During this
>>> period, the
>>> mm_cids should be spanning all numbers between 0 and nproc.
>>>
>>> At the end of this phase, a thread with high enough mm_cid (>=
>>> nproc/2)
>>> is selected to be the new leader, all other threads terminate.
>>>
>>> After some time, the only running thread should see 0 as mm_cid, if
>>> that
>>> doesn't happen, the compaction mechanism didn't work and the test
>>> fails.
>>>
>>> The test never fails if only 1 core is available, in which case, we
>>> cannot test anything as the only available mm_cid is 0.
>>>
>>> To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>>
>> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>>
>> tiny nit below:
>>
>>> +		usleep(RUNNER_PERIOD);
>>> +	curr_mm_cid = rseq_current_mm_cid();
>>> +	/*
>>> +	 * We select one thread with high enough mm_cid to be the
>>> new leader
>>
>> Missing punctuation here (...new leader.  All other...)
> 
> I guess I'm allergic to those ;) Thanks for finding it!
> I wonder if checkpatch should be able to catch this kind of problem,
> but that's for another day.
> 
> Do I need to send a v6 for this or just reply here with the fixed
> patch?

Please send v6 with the suggested changes. Also change the commit
summary to

"selftests/rseq"

thanks,
-- Shuah