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

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Message-ID: <2c2ee65283893a433ac4488f3d048b0f7454be24.camel@redhat.com>
Date: Mon, 10 Feb 2025 16:25:59 +0100
From: Gabriele Monaco <gmonaco@...hat.com>
To: 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
Subject: Re: [PATCH v5 3/3] rseq/selftests: Add test for mm_cid compaction



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?

Thanks,
Gabriele