Commit 13924d2a authored by Juri Lelli's avatar Juri Lelli Committed by Ingo Molnar

Documentation/scheduler/sched-deadline.txt: Add minimal main() appendix

Add an appendix providing a simple self-contained code snippet
showing how SCHED_DEADLINE reservations can be created by
application developers.
Signed-off-by: default avatarJuri Lelli <juri.lelli@arm.com>
Reviewed-by: default avatarHenrik Austad <henrik@austad.us>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dario Faggioli <raistlin@linux.it>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1410256636-26171-6-git-send-email-juri.lelli@arm.com
[ Fixed some whitespace inconsistencies. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f5801933
......@@ -16,6 +16,7 @@ CONTENTS
5.1 SCHED_DEADLINE and cpusets HOWTO
6. Future plans
A. Test suite
B. Minimal main()
0. WARNING
......@@ -397,3 +398,128 @@ Appendix A. Test suite
application, given that you know its pid:
# schedtool -E -t 10000000:100000000 my_app_pid
Appendix B. Minimal main()
==========================
We provide in what follows a simple (ugly) self-contained code snippet
showing how SCHED_DEADLINE reservations can be created by a real-time
application developer.
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <linux/unistd.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <sys/syscall.h>
#include <pthread.h>
#define gettid() syscall(__NR_gettid)
#define SCHED_DEADLINE 6
/* XXX use the proper syscall numbers */
#ifdef __x86_64__
#define __NR_sched_setattr 314
#define __NR_sched_getattr 315
#endif
#ifdef __i386__
#define __NR_sched_setattr 351
#define __NR_sched_getattr 352
#endif
#ifdef __arm__
#define __NR_sched_setattr 380
#define __NR_sched_getattr 381
#endif
static volatile int done;
struct sched_attr {
__u32 size;
__u32 sched_policy;
__u64 sched_flags;
/* SCHED_NORMAL, SCHED_BATCH */
__s32 sched_nice;
/* SCHED_FIFO, SCHED_RR */
__u32 sched_priority;
/* SCHED_DEADLINE (nsec) */
__u64 sched_runtime;
__u64 sched_deadline;
__u64 sched_period;
};
int sched_setattr(pid_t pid,
const struct sched_attr *attr,
unsigned int flags)
{
return syscall(__NR_sched_setattr, pid, attr, flags);
}
int sched_getattr(pid_t pid,
struct sched_attr *attr,
unsigned int size,
unsigned int flags)
{
return syscall(__NR_sched_getattr, pid, attr, size, flags);
}
void *run_deadline(void *data)
{
struct sched_attr attr;
int x = 0;
int ret;
unsigned int flags = 0;
printf("deadline thread started [%ld]\n", gettid());
attr.size = sizeof(attr);
attr.sched_flags = 0;
attr.sched_nice = 0;
attr.sched_priority = 0;
/* This creates a 10ms/30ms reservation */
attr.sched_policy = SCHED_DEADLINE;
attr.sched_runtime = 10 * 1000 * 1000;
attr.sched_period = attr.sched_deadline = 30 * 1000 * 1000;
ret = sched_setattr(0, &attr, flags);
if (ret < 0) {
done = 0;
perror("sched_setattr");
exit(-1);
}
while (!done) {
x++;
}
printf("deadline thread dies [%ld]\n", gettid());
return NULL;
}
int main (int argc, char **argv)
{
pthread_t thread;
printf("main thread [%ld]\n", gettid());
pthread_create(&thread, NULL, run_deadline, NULL);
sleep(10);
done = 1;
pthread_join(thread, NULL);
printf("main dies [%ld]\n", gettid());
return 0;
}
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