Re: [PATCH] sched: fix RLIMIT_RTTIME when PI-boosting to RT

From: Ingo Molnar
Date: Tue Mar 10 2015 - 01:43:03 EST



* Brian Silverman <brian@xxxxxxxxxxxxxxxx> wrote:

> Here's my test code. Compile with `gcc -pthread -lrt test_pi.c`. It
> requires permission to set a realtime scheduling policy of 2 when
> running.

Mind sending a patch that sticks this testcase into
tools/testing/selftests/sched/ or so, with the new 'sched' directory
and new Makefile to be created by you as well?

I've reformatted the testcase below, to kernel coding style. Note that
I added a minimal license notification, you might want to add your
copyright.

Thanks,

Ingo

==========================>


/*
* RLIMIT_RTTIME test code. Compile with:
*
* gcc -pthread -lrt test_pi.c
*
* It requires permission to set a realtime scheduling policy of 2 when running.
*
* License: GPLv2
*/
#define _GNU_SOURCE

#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <sched.h>
#include <assert.h>
#include <sys/resource.h>
#include <string.h>
#include <signal.h>
#include <stdlib.h>

static const struct timespec kSleepTime = { 0, 10000 };

static pthread_mutex_t mutex;

extern void nop()
{
}

void *nonrealtime(void *ignored_param)
{
while (1) {
assert(pthread_mutex_lock(&mutex) == 0);
assert(pthread_mutex_unlock(&mutex) == 0);
assert(clock_nanosleep(CLOCK_MONOTONIC, 0, &kSleepTime, NULL) == 0);
}
}

void *realtime(void *ignored_param)
{
struct sched_param param;

memset(&param, 0, sizeof(param));
param.sched_priority = 2;
assert(sched_setscheduler(0, SCHED_FIFO, &param) == 0);

while (1) {
assert(pthread_mutex_lock(&mutex) == 0);
assert(clock_nanosleep(CLOCK_MONOTONIC, 0, &kSleepTime, NULL) == 0);
assert(pthread_mutex_unlock(&mutex) == 0);
}
}

void signal_handler(int number)
{
printf("got signal %d, SIGXCPU=%d\n", number, SIGXCPU);

exit(0);
}

int main()
{
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_handler = signal_handler;
assert(sigaction(SIGXCPU, &action, NULL) == 0);

struct rlimit rlim;
rlim.rlim_cur = 500;
rlim.rlim_max = 5000;
assert(prlimit(0, RLIMIT_RTTIME, &rlim, NULL) == 0);

pthread_mutexattr_t mutexattr;
assert(pthread_mutexattr_init(&mutexattr) == 0);
assert(pthread_mutexattr_setprotocol(&mutexattr, PTHREAD_PRIO_INHERIT) == 0);
assert(pthread_mutex_init(&mutex, &mutexattr) == 0);
assert(pthread_mutexattr_destroy(&mutexattr) == 0);

pthread_t nrt, rt;
assert(pthread_create(&nrt, NULL, nonrealtime, NULL) == 0);
assert(pthread_create(&rt, NULL, realtime, NULL) == 0);
assert(pthread_join(nrt, NULL) == 0);
assert(pthread_join(rt, NULL) == 0);

return 0;
}
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