Re: [PATCH v5 v6.11 v5.15 v5.4 v4.19 1/1] selftests: breakpoints: use remaining time to check if suspend succeed

[Shuah Khan <skhan@linuxfoundation.org>]

On 9/30/24 16:40, Yifei Liu wrote:
> step_after_suspend_test fails with device busy error while
> writing to /sys/power/state to start suspend. The test believes
> it failed to enter suspend state with
> 
> $ sudo ./step_after_suspend_test
> TAP version 13
> Bail out! Failed to enter Suspend state
> 
> However, in the kernel message, I indeed see the system get
> suspended and then wake up later.
> 
> [611172.033108] PM: suspend entry (s2idle)
> [611172.044940] Filesystems sync: 0.006 seconds
> [611172.052254] Freezing user space processes
> [611172.059319] Freezing user space processes completed (elapsed 0.001 seconds)
> [611172.067920] OOM killer disabled.
> [611172.072465] Freezing remaining freezable tasks
> [611172.080332] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
> [611172.089724] printk: Suspending console(s) (use no_console_suspend to debug)
> [611172.117126] serial 00:03: disabled
> some other hardware get reconnected
> [611203.136277] OOM killer enabled.
> [611203.140637] Restarting tasks ...
> [611203.141135] usb 1-8.1: USB disconnect, device number 7
> [611203.141755] done.
> [611203.155268] random: crng reseeded on system resumption
> [611203.162059] PM: suspend exit
> 
> After investigation, I noticed that for the code block
> if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem"))
> 	ksft_exit_fail_msg("Failed to enter Suspend state\n");
> 
> The write will return -1 and errno is set to 16 (device busy).
> It should be caused by the write function is not successfully returned
> before the system suspend and the return value get messed when waking up.
> As a result, It may be better to check the time passed of those few
> instructions to determine whether the suspend is executed correctly for
> it is pretty hard to execute those few lines for 5 seconds.
> 
> The timer to wake up the system is set to expire after 5 seconds and
> no re-arm. If the timer remaining time is 0 second and 0 nano secomd,
> it means the timer expired and wake the system up. Otherwise, the system
> could be considered to enter the suspend state failed if there is any
> remaining time.
> 
> After appling this patch, the test would not fail for it believes the
> system does not go to suspend by mistake. It now could continue to the
> rest part of the test after suspend.
> 
> Fixes: bfd092b8c272 ("selftests: breakpoint: add step_after_suspend_test")
> Reported-by: Sinadin Shan <sinadin.shan@oracle.com>
> Signed-off-by: Yifei Liu <yifei.l.liu@oracle.com>
> ---
> v4->v5: Remove the above quotes in the first part.
> remove the incorrect format which could confuse the git.

Applied to linux-kselftest fixes branch for next rc.

thanks,
-- Shuah