On Tue, Apr 9, 2024 at 6:39 AM Oleg Nesterov oleg@redhat.com wrote:
Thomas says:
The signal distribution test has a tendency to hang for a long time as the signal delivery is not really evenly distributed. In fact it might never be distributed across all threads ever in the way it is written.To me even the
This primarily tests that the kernel does not favour any one.comment doesn't look right. The kernel does favour a thread which hits the timer interrupt when CLOCK_PROCESS_CPUTIME_ID expires.
The new version simply checks that the group leader sleeping in join() never receives SIGALRM, cpu_timer_fire() should always send the signal to the thread which burns cpu.
Without the commit bcb7ee79029d ("posix-timers: Prefer delivery of signals to the current thread") the test-case fails immediately, the very 1st tick wakes the leader up. Otherwise it quickly succeeds after 100 ticks.
As Thomas suggested, the new version doesn't report the failure on the pre v6.3 kernels that do not have the commit bcb7ee79029d; this is a feature that obviously fails on the older kernels. So the patch adds the new simple ksft_ck_kernel_version() helper and uses ksft_test_result_skip() if check_timer_distribution() fails on the older kernel.
Signed-off-by: Oleg Nesterov oleg@redhat.com
This is working great here (on both 6.6 and the older 6.1)! Thanks so much for fixing this! One nit below, but otherwise: Tested-by: John Stultz jstultz@google.com
+err:
ksft_print_msg(errmsg);
This bit is causing the following warning: posix_timers.c:250:2: warning: format not a string literal and no format arguments [-Wformat-security] 250 | ksft_print_msg(errmsg); | ^~~~~~~~~~~~~~
A simple fix is just to switch it to: ksft_print_msg("%s", errmsg);
thanks -john