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

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

Documentation/scheduler/sched-deadline.txt

+126 −0
Original line number Diff line number Diff line
@@ -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;

 }