@@ -18,6 +18,7 @@
#include <sys/timerfd.h>
#include <sys/types.h>
#include <sys/wait.h>
+#include <time.h>
#include "../kselftest.h"
@@ -133,6 +134,7 @@ void suspend(void)
int timerfd;
int err;
struct itimerspec spec = {};
+ clock_t t;
if (getuid() != 0)
ksft_exit_skip("Please run the test as root - Exiting.\n");
@@ -152,8 +154,11 @@ void suspend(void)
if (err < 0)
ksft_exit_fail_msg("timerfd_settime() failed\n");
- if (write(power_state_fd, "mem", strlen("mem")) != strlen("mem"))
- ksft_exit_fail_msg("Failed to enter Suspend state\n");
+ t = clock();
+ write(power_state_fd, "mem", strlen("mem"));
+ t = clock()-t;
+ if ((int)(t) < 4)
+ ksft_exit_fail_msg("Failed to enter Suspend state %d\n",errno);
close(timerfd);
close(power_state_fd);
We recently notice that the step_after_suspend_test would fail on our plenty devices. The test believesit 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 notice 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 4 seconds, or even more if it is not long enough. 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> --- .../selftests/breakpoints/step_after_suspend_test.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)