Thank you!
Yiei
> On Oct 2, 2024, at 1:38 PM, Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
>> Signed-off-by: Yifei Liu <yifei.l.liu@xxxxxxxxxx>
>> ---
>> 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
