linux-kernel - Re: [RESEND PATCH v13 3/3] selftests/rseq: Add test for mm

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Message-ID: <70fe4209-4a31-4957-a658-727081f8291a@redhat.com>
Date: Fri, 20 Jun 2025 17:20:38 +0000 (UTC)
From: Gabriele Monaco <gmonaco@...hat.com>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
	Ingo Molnar <mingo@...hat.org>
Subject: Re: [RESEND PATCH v13 3/3] selftests/rseq: Add test for mm_cid
 compaction

2025-06-18T21:04:30Z Shuah Khan <skhan@...uxfoundation.org>:

> On 6/13/25 03:12, 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.
>> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>> Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
>
> Mathieu,
>
> Let me know if you would like me to take this through my tree.
>
> Acked-by: Shuah Khan <skhan@...uxfoundation.org>

Thanks for the Ack, just to add some context: the test is flaky without the previous patches, would it still be alright to pull it before them?

Thanks,
Gabriele