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From:   Alistair Popple <apopple@nvidia.com>
To:     Ryan Roberts <ryan.roberts@arm.com>
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Subject: Re: [RESEND PATCH v7 05/10] selftests/mm/kugepaged: Restore thp
 settings at exit
Date:   Thu, 23 Nov 2023 16:54:41 +1100
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Ryan Roberts <ryan.roberts@arm.com> writes:

> Previously, the saved thp settings would be restored upon a signal or at
> the natural end of the test suite. But there are some tests that
> directly call exit() upon failure. In this case, the thp settings were
> not being restored, which could then influence other tests.
>
> Fix this by installing an atexit() handler to do the actual restore. The
> signal handler can now just call exit() and the atexit handler is
> invoked.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Reviewed-by: Alistair Popple <apopple@nvidia.com>

> ---
>  tools/testing/selftests/mm/khugepaged.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index 030667cb5533..fc47a1c4944c 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -374,18 +374,22 @@ static void pop_settings(void)
>  	write_settings(current_settings());
>  }
>
> -static void restore_settings(int sig)
> +static void restore_settings_atexit(void)
>  {
>  	if (skip_settings_restore)
> -		goto out;
> +		return;
>
>  	printf("Restore THP and khugepaged settings...");
>  	write_settings(&saved_settings);
>  	success("OK");
> -	if (sig)
> -		exit(EXIT_FAILURE);
> -out:
> -	exit(exit_status);
> +
> +	skip_settings_restore = true;
> +}
> +
> +static void restore_settings(int sig)
> +{
> +	/* exit() will invoke the restore_settings_atexit handler. */
> +	exit(sig ? EXIT_FAILURE : exit_status);
>  }
>
>  static void save_settings(void)
> @@ -415,6 +419,7 @@ static void save_settings(void)
>
>  	success("OK");
>
> +	atexit(restore_settings_atexit);
>  	signal(SIGTERM, restore_settings);
>  	signal(SIGINT, restore_settings);
>  	signal(SIGHUP, restore_settings);