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Date: Tue, 9 Sep 2014 10:57:16 +0100
From: Juri Lelli <juri.lelli@....com>
To: peterz@...radead.org
Cc: luca.abeni@...tn.it, rdunlap@...radead.org, mingo@...hat.com,
henrik@...tad.us, raistlin@...ux.it, juri.lelli@...il.com,
juri.lelli@....com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 5/5] 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: Juri Lelli <juri.lelli@....com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Henrik Austad <henrik@...tad.us>
Cc: Dario Faggioli <raistlin@...ux.it>
Cc: Juri Lelli <juri.lelli@...il.com>
Cc: linux-doc@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
Documentation/scheduler/sched-deadline.txt | 126 +++++++++++++++++++++++++++++
1 file changed, 126 insertions(+)
diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
index b4aad31..cd8274c 100644
--- a/Documentation/scheduler/sched-deadline.txt
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -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;
+ }
--
2.0.4
--
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