[v3,v6.11,v5.15,v5.4,v4.19,1/1] selftests: breakpoints: use remaining time to check if suspend succeed

"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: bfd092b8c2728 ("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>
---
 .../testing/selftests/breakpoints/step_after_suspend_test.c  | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

On 9/23/24 16:50, 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: bfd092b8c2728 ("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>
> ---
>   .../testing/selftests/breakpoints/step_after_suspend_test.c  | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/breakpoints/step_after_suspend_test.c b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> index dfec31fb9b30d..33f5542bf741d 100644
> --- a/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> +++ b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> @@ -152,7 +152,10 @@ void suspend(void)
>   	if (err < 0)
>   		ksft_exit_fail_msg("timerfd_settime() failed\n");
>   
> -	if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem"))
> +	system("(echo mem > /sys/power/state) 2> /dev/null");
> +
> +	timerfd_gettime(timerfd,&spec);
> +	if (spec.it_value.tv_sec != 0 || spec.it_value.tv_nsec != 0)
>   		ksft_exit_fail_msg("Failed to enter Suspend state\n");
>   
>   	close(timerfd);

I am seeing coding style errors. Please run checkpatch script to find
them - fix and send v4.


ERROR: space required after that ',' (ctx:VxO)
#168: FILE: tools/testing/selftests/breakpoints/step_after_suspend_test.c:157:
+	timerfd_gettime(timerfd,&spec);
  	                       ^

ERROR: space required before that '&' (ctx:OxV)
#168: FILE: tools/testing/selftests/breakpoints/step_after_suspend_test.c:157:
+	timerfd_gettime(timerfd,&spec);
  	                        ^

thanks,
-- Shuah