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

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Message-ID: <2606da6a-3a13-4db6-855e-8dcc61c45b45@linuxfoundation.org>
Date: Wed, 18 Jun 2025 15:04:22 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Gabriele Monaco <gmonaco@...hat.com>, 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
Cc: Ingo Molnar <mingo@...hat.org>, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [RESEND PATCH v13 3/3] selftests/rseq: Add test for mm_cid
 compaction

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,
-- Shuah