linux-kernel - Re: [PATCH] selftests: breakpoints: use suspend

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Message-ID: <78cd5960-ea18-4e18-9f13-fb3c513014f2@linuxfoundation.org>
Date: Thu, 10 Jul 2025 14:25:38 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Moon Hee Lee <moonhee.lee.ca@...il.com>, shuah@...nel.org
Cc: yifei.l.liu@...cle.com, zhujun2@...s.chinamobile.com,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kernel-mentees@...ts.linux.dev, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] selftests: breakpoints: use suspend_stats to reliably
 check suspend success

On 6/26/25 13:16, Moon Hee Lee wrote:
> The step_after_suspend_test verifies that the system successfully
> suspended and resumed by setting a timerfd and checking whether the
> timer fully expired. However, this method is unreliable due to timing
> races.
> 
> In practice, the system may take time to enter suspend, during which the
> timer may expire just before or during the transition. As a result,
> the remaining time after resume may show non-zero nanoseconds, even if
> suspend/resume completed successfully. This leads to false test failures.
> 
> Replace the timer-based check with a read from
> /sys/power/suspend_stats/success. This counter is incremented only
> after a full suspend/resume cycle, providing a reliable and race-free
> indicator.
> 
> Also remove the unused file descriptor for /sys/power/state, which
> remained after switching to a system() call to trigger suspend [1].
> 
> [1] https://lore.kernel.org/all/20240930224025.2858767-1-yifei.l.liu@oracle.com/
> 
> Fixes: c66be905cda2 ("selftests: breakpoints: use remaining time to check if suspend succeed")
> Signed-off-by: Moon Hee Lee <moonhee.lee.ca@...il.com>
> ---

Applied to linux-kselftest next branch for Linux 6.17-rc1

thanks,
-- Shuah