[PATCH v2] selftests/powerpc: Avoid remaining process/threads

[Breno Leitao]

Hello Michael,

On 08/06/2018 08:06 AM, Michael Ellerman wrote:
> Breno Leitao <leitao at debian.org> writes:
> 
>> diff --git a/tools/testing/selftests/powerpc/harness.c b/tools/testing/selftests/powerpc/harness.c
>> index 66d31de60b9a..06c51e8d8ccb 100644
>> --- a/tools/testing/selftests/powerpc/harness.c
>> +++ b/tools/testing/selftests/powerpc/harness.c
>> @@ -85,13 +85,16 @@ int run_test(int (test_function)(void), char *name)
>>  	return status;
>>  }
>>  
>> -static void alarm_handler(int signum)
>> +static void sig_handler(int signum)
>>  {
>> -	/* Jut wake us up from waitpid */
>> +	if (signum == SIGINT)
>> +		kill(-pid, SIGTERM);
> 
> I don't think we need to do that here, if we just return then we'll pop
> out of the waitpid() and go via the normal path.

Correct, if we press ^C while the parent process is waiting at waitpid(),
then waitpid() syscall will be interrupted (EINTR) and never restarted again
(unless we set sa_flags = SA_RESTART), thus, the code will restart to execute
the next instruction when the signal handler is done, as we had skipped
waitpid().

>From a theoretical point of view, the user can press ^C before the process
executes waitpid() syscall. In this case and the process will not 'skip' the
waitpid(), which will continue to wait. We can clearly force this behavior
putting a sleep(1) before waitpid() and pressing  ^C in the very first
second, it will 'skip' the nanosleep() syscall instead of waitpid() which
will be there, and the ^C will be ignored (thus not calling kill(-pid, SIGTERM)).

>From a practical point of view, I will prepare a v3 patch. :-)