linux-kernel - Re: [PATCH] selftests: breakpoints: check RTC wakeup alarm support before test

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Message-ID: <b0ceed9c-3ff6-4eee-80e3-f50631bb1230@linuxfoundation.org>
Date: Wed, 19 Nov 2025 15:15:02 -0700
From: Shuah Khan <skhan@...uxfoundation.org>
To: Xinyu Zheng <zhengxinyu6@...wei.com>, Shuah Khan <shuah@...nel.org>
Cc: Moon Hee Lee <moonhee.lee.ca@...il.com>, yifei.l.liu@...cle.com,
 zhujun2@...s.chinamobile.com, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, zouyipeng@...wei.com,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] selftests: breakpoints: check RTC wakeup alarm support
 before test

On 11/11/25 23:15, Xinyu Zheng wrote:
> If RTC wakeup alarm feature is unsupported, this testcase may cause

It may cause infinite suspend? Doesn't sound definitive.> infinite suspend if there is no other wakeup source. To solve this
> problem, set wakeup alarm up before we trigger suspend. In this case,
> we can test if RTC support RTC_FEATURE_ALARM and efi_set_alarm function.
> 

For a "may cause" problem, this change> Signed-off-by: Xinyu Zheng <zhengxinyu6@...wei.com>
> --->   .../breakpoints/step_after_suspend_test.c     | 23 +++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/tools/testing/selftests/breakpoints/step_after_suspend_test.c b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> index 8d233ac95696..e738af896ce1 100644
> --- a/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> +++ b/tools/testing/selftests/breakpoints/step_after_suspend_test.c
> @@ -13,6 +13,8 @@
>   #include <stdio.h>
>   #include <string.h>
>   #include <unistd.h>
> +#include <linux/rtc.h>
> +#include <sys/ioctl.h>
>   #include <sys/ptrace.h>
>   #include <sys/stat.h>
>   #include <sys/timerfd.h>
> @@ -159,10 +161,30 @@ void suspend(void)
>   	int count_before;
>   	int count_after;
>   	struct itimerspec spec = {};
> +	char *rtc_file = "/dev/rtc0";
> +	int rtc_fd;
> +	struct rtc_wkalrm alarm = { 0 };
> +	time_t secs;
>   
>   	if (getuid() != 0)
>   		ksft_exit_skip("Please run the test as root - Exiting.\n");
>   
> +	rtc_fd = open(rtc_file, O_RDONLY);
> +	if (rtc_fd < 0)
> +		ksft_exit_fail_msg("open rtc0 failed\n");
> +
> +	err = ioctl(rtc_fd, RTC_RD_TIME, &alarm.time);
> +	if (err < 0)
> +		ksft_exit_fail_msg("get rtc time failed\n");
> +
> +	secs = timegm((struct tm *)&alarm.time) + 3;
> +	gmtime_r(&secs, (struct tm *)&alarm.time);
> +	alarm.enabled = 1;
> +
> +	err = ioctl(rtc_fd, RTC_WKALM_SET, &alarm);
> +	if (err < 0)
> +		ksft_exit_fail_msg("set wake alarm test failed, errno %d\n", errno);

Essentially with this change the test doesn't run unless
RTC wake is supported. That sounds restrictive - is there
another way do do this?

> +
>   	timerfd = timerfd_create(CLOCK_BOOTTIME_ALARM, 0);
>   	if (timerfd < 0)
>   		ksft_exit_fail_msg("timerfd_create() failed\n");
> @@ -180,6 +202,7 @@ void suspend(void)
>   	if (count_after <= count_before)
>   		ksft_exit_fail_msg("Failed to enter Suspend state\n");
>   
> +	close(rtc_fd);
>   	close(timerfd);
>   }
>  
thanks,
-- Shuah