linux-kernel - Re: [PATCH v6 2/2] selftests/timers/posix_timers: Test delivery of signals across threads

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Message-ID: <a282446a-6e37-4be7-bb9c-e268c99656b6@collabora.com>
Date: Sun, 7 Apr 2024 02:32:14 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Marco Elver <elver@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
 "Eric W. Biederman" <ebiederm@...ssion.com>, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
 kasan-dev@...glegroups.com
Subject: Re: [PATCH v6 2/2] selftests/timers/posix_timers: Test delivery of
 signals across threads

On 4/7/24 2:13 AM, Oleg Nesterov wrote:
> Muhammad,
> 
> I am sorry, but... are you aware that this patch was applied over a year ago,
> and then this code was updated to use the ksft_API?
Sorry, didn't realized this is already applied. So this patch is already
applied and it has already been made compliant.

Thanks

> 
> Oleg.
> 
> On 04/07, Muhammad Usama Anjum wrote:
>>
>> On 3/16/23 5:30 PM, Marco Elver wrote:
>>> From: Dmitry Vyukov <dvyukov@...gle.com>
>>>
>>> Test that POSIX timers using CLOCK_PROCESS_CPUTIME_ID eventually deliver
>>> a signal to all running threads.  This effectively tests that the kernel
>>> doesn't prefer any one thread (or subset of threads) for signal delivery.
>>>
>>> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
>>> Signed-off-by: Marco Elver <elver@...gle.com>
>>> ---
>>> v6:
>>> - Update wording on what the test aims to test.
>>> - Fix formatting per checkpatch.pl.
>>> ---
>>>  tools/testing/selftests/timers/posix_timers.c | 77 +++++++++++++++++++
>>>  1 file changed, 77 insertions(+)
>>>
>>> diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
>>> index 0ba500056e63..8a17c0e8d82b 100644
>>> --- a/tools/testing/selftests/timers/posix_timers.c
>>> +++ b/tools/testing/selftests/timers/posix_timers.c
>>> @@ -188,6 +188,80 @@ static int check_timer_create(int which)
>>>  	return 0;
>>>  }
>>>  
>>> +int remain;
>>> +__thread int got_signal;
>>> +
>>> +static void *distribution_thread(void *arg)
>>> +{
>>> +	while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
>>> +	return NULL;
>>> +}
>>> +
>>> +static void distribution_handler(int nr)
>>> +{
>>> +	if (!__atomic_exchange_n(&got_signal, 1, __ATOMIC_RELAXED))
>>> +		__atomic_fetch_sub(&remain, 1, __ATOMIC_RELAXED);
>>> +}
>>> +
>>> +/*
>>> + * Test that all running threads _eventually_ receive CLOCK_PROCESS_CPUTIME_ID
>>> + * timer signals. This primarily tests that the kernel does not favour any one.
>>> + */
>>> +static int check_timer_distribution(void)
>>> +{
>>> +	int err, i;
>>> +	timer_t id;
>>> +	const int nthreads = 10;
>>> +	pthread_t threads[nthreads];
>>> +	struct itimerspec val = {
>>> +		.it_value.tv_sec = 0,
>>> +		.it_value.tv_nsec = 1000 * 1000,
>>> +		.it_interval.tv_sec = 0,
>>> +		.it_interval.tv_nsec = 1000 * 1000,
>>> +	};
>>> +
>>> +	printf("Check timer_create() per process signal distribution... ");
>> Use APIs from kselftest.h. Use ksft_print_msg() here.
>>
>>> +	fflush(stdout);
>>> +
>>> +	remain = nthreads + 1;  /* worker threads + this thread */
>>> +	signal(SIGALRM, distribution_handler);
>>> +	err = timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
>>> +	if (err < 0) {
>>> +		perror("Can't create timer\n");
>> ksft_perror() here
>>
>>> +		return -1;
>>> +	}
>>> +	err = timer_settime(id, 0, &val, NULL);
>>> +	if (err < 0) {
>>> +		perror("Can't set timer\n");
>>> +		return -1;
>>> +	}
>>> +
>>> +	for (i = 0; i < nthreads; i++) {
>>> +		if (pthread_create(&threads[i], NULL, distribution_thread, NULL)) {
>>> +			perror("Can't create thread\n");
>>> +			return -1;
>>> +		}
>>> +	}
>>> +
>>> +	/* Wait for all threads to receive the signal. */
>>> +	while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
>>> +
>>> +	for (i = 0; i < nthreads; i++) {
>>> +		if (pthread_join(threads[i], NULL)) {
>>> +			perror("Can't join thread\n");
>>> +			return -1;
>>> +		}
>>> +	}
>>> +
>>> +	if (timer_delete(id)) {
>>> +		perror("Can't delete timer\n");
>>> +		return -1;
>>> +	}
>>> +
>>> +	printf("[OK]\n");
>> ksft_test_result or _pass variant as needed?
>>
>>> +	return 0;
>>> +}
>>> +
>>>  int main(int argc, char **argv)
>>>  {
>>>  	printf("Testing posix timers. False negative may happen on CPU execution \n");
>>> @@ -217,5 +291,8 @@ int main(int argc, char **argv)
>>>  	if (check_timer_create(CLOCK_PROCESS_CPUTIME_ID) < 0)
>>>  		return ksft_exit_fail();
>>>  
>>> +	if (check_timer_distribution() < 0)
>>> +		return ksft_exit_fail();
>>> +
>>>  	return ksft_exit_pass();
>>>  }
>>
>> -- 
>> BR,
>> Muhammad Usama Anjum
>>
> 

-- 
BR,
Muhammad Usama Anjum