linux-kernel - Re: [PATCH] tools/testing/selftests/livepatch: define max test-syscall processes

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Date: Wed, 29 May 2024 18:09:04 -0300
From: Marcos Paulo de Souza <mpdesouza@...e.com>
To: Ryan Sullivan <rysulliv@...hat.com>
Cc: mpdesouza@...e.com,
	live-patching@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	jpoimboe@...nel.org,
	jikos@...nel.org,
	mbenes@...e.cz,
	pmladek@...e.com,
	joe.lawrence@...hat.com,
	shuah@...nel.org
Subject: Re: [PATCH] tools/testing/selftests/livepatch: define max test-syscall processes

From: mpdesouza@...e.com

On Wed, 29 May 2024 16:19:41 -0400 Ryan Sullivan <rysulliv@...hat.com> wrote:

> Define a maximum allowable number of pids that can be livepatched in
> test-syscall.sh as with extremely large machines the output from a
> large number of processes overflows the dev/kmsg "expect" buffer in
> the "check_result" function and causes a false error.

I believe that 128 threads hammering getpid is good enough :)

Tested-by: Marcos Paulo de Souza <mpdesouza@...e.com>
Reviewed-by: Marcos Paulo de Souza <mpdesouza@...e.com>

> 
> Reported-by: CKI Project <cki-project@...hat.com>
> Signed-off-by: Ryan Sullivan <rysulliv@...hat.com>
> ---
>  tools/testing/selftests/livepatch/test-syscall.sh | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/livepatch/test-syscall.sh b/tools/testing/selftests/livepatch/test-syscall.sh
> index b76a881d4013..289eb7d4c4b3 100755
> --- a/tools/testing/selftests/livepatch/test-syscall.sh
> +++ b/tools/testing/selftests/livepatch/test-syscall.sh
> @@ -15,7 +15,10 @@ setup_config
>  
>  start_test "patch getpid syscall while being heavily hammered"
>  
> -for i in $(seq 1 $(getconf _NPROCESSORS_ONLN)); do
> +NPROC=$(getconf _NPROCESSORS_ONLN)
> +MAXPROC=128
> +
> +for i in $(seq 1 $(($NPROC < $MAXPROC ? $NPROC : $MAXPROC))); do
>  	./test_klp-call_getpid &
>  	pids[$i]="$!"
>  done
> -- 
> 2.44.0