#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
pthread_t t1; /* prio 1 */
pthread_t t2; /* prio 6 */
pthread_t t3; /* prio 11 */
static volatile int state = 0;
void *
run1(void *arg)
{
struct sched_param sparam;
int policy, i, j=0, count=0, y=0;
long start, end, diff;
fprintf(stderr, "thread 1 - start\n");
start = diff = time(NULL);
state = 1; /* allow thread 2 to start */
do {
if (!pthread_getschedparam (pthread_self(), &policy, &sparam)
&& (sparam.sched_priority != 1)) { /* got bumped by t3 */
if (count == 0) {
fprintf(stderr, "thread 1 - lowering priority after being bumped by t3\n");
sparam.sched_priority = 1;
if (pthread_setschedparam (pthread_self(), policy, &sparam)) {
perror("pthread_setschedparam"); return (void *)-2;
}
++count;
}
}
for (i=0; i<1000; i++) {
j += j*i;
}
end = time(NULL);
if ((end-diff)>=2) {
fprintf(stderr, "thread 1 - continue busy loop\n");
diff = end;
if (!y) { ++y; pthread_yield(); /* once */}
}
} while ((end-start) < 10);
fprintf(stderr, "thread 1 - done\n");
return NULL;
}
void *
run2(void *arg)
{
long start, end, diff;
int i, j=0, y=0;
fprintf(stderr, "thread 2 - start\n");
start = diff = time(NULL);
state = 2;
do {
for (i=0; i<10000; i++) j+=i;
end = time(NULL);
if ((end-diff)>=2) {
fprintf(stderr, "thread 2 - continue busy loop\n");
diff = end;
if (!y) { ++y; pthread_yield(); /* once */}
}
} while ((end-start) < 10);
fprintf(stderr, "thread 2 - done\n");
return NULL;
}
void *
run3(void *arg)
{
struct sched_param sp1, sp2;
int policy, i;
long start, end, diff, j=0;
fprintf(stderr, "thread 3 - start\n");
i = 0;
start = diff = time(NULL);
do {
fprintf(stderr, "thread 3 - checking for priority of t1\n");
if (!pthread_getschedparam (t1, &policy, &sp1) &&
!pthread_getschedparam (t3, &policy, &sp2) &&
(sp1.sched_priority < sp2.sched_priority)) {
fprintf(stderr, "thread 3 - bumping prio of t1 from %d to %d\n", sp1.sched_priority, sp2.sched_priority);
if (pthread_setschedparam (t1, policy, &sp2)) {
perror("pthread_setschedparam"); return (void *)-2;
}
}
for (i=0; i<10000; i++) {
j += j*i;
}
end = time(NULL);
if ((end-diff)>=2) {
fprintf(stderr, "thread 3 - continue busy loop\n");
diff = end;
}
} while ((end-start) < 10);
fprintf(stderr, "thread 3 - done\n");
return NULL;
}
int
main()
{
pthread_attr_t attr;
struct sched_param sched_param;
if (pthread_attr_init(&attr) != 0) return -1;
if (pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED) != 0) return -1;
{
int policy = SCHED_RR;
sched_param.sched_priority = 12;
if (pthread_setschedparam(pthread_self(), policy, &sched_param) != 0) return -1;
if (pthread_getschedparam(pthread_self(), &policy, &sched_param) != 0) return -1;
}
if (pthread_attr_setschedpolicy(&attr, SCHED_RR) != 0) return -1;
/* create t1 prio 1 */
fprintf(stderr, "creating thread 1\n");
sched_param.sched_priority = 1;
if (pthread_attr_setschedparam(&attr, &sched_param) != 0) return -1;
if (0 != pthread_create(&t1, &attr, run1, NULL)) {
perror("pthread_create"); return -4;
}
while (state != 1) usleep(3);
/* create t2 prio 6 */
fprintf(stderr, "creating thread 2\n");
sched_param.sched_priority = 6;
if (pthread_attr_setschedparam(&attr, &sched_param) != 0) return -1;
if (0 != pthread_create(&t2, &attr, run2, NULL)) {
perror("pthread_create"); return -5;
}
while (state != 2) usleep(3);
/* create t3 prio 11 */
fprintf(stderr, "creating thread 3\n");
sched_param.sched_priority = 11;
if (pthread_attr_setschedparam(&attr, &sched_param) != 0) return -1;
if (0 != pthread_create(&t3, &attr, run3, NULL)) {
perror("pthread_create"); return -6;
}
/* let them run */
pthread_join(t1, NULL);
pthread_join(t2, NULL);
pthread_join(t3, NULL);
return 0;
}