Messages in this thread | | | Date | Thu, 13 Jul 2006 08:29:07 +0200 | From | Olivier Croquette <> | Subject | Scheduling parameters of a process and its main thread |
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Hi
When a process only has one thread, I would expect that sched_get* and pthread_getschedparam return equivalent priorities.
But in the example below, it's not the case. What I do: - print priorities - give RT priority to the process - print priorities - give RT priority to the thread - print priorities
1. Process 3938 : policy=0 prio=0 1. Thread 1075147872 : policy=0 prio=0
2. Process 3938 : policy=1 prio=20 2. Thread 1075147872 : policy=0 prio=0
3. Process 3938 : policy=1 prio=30 3. Thread 1075147872 : policy=1 prio=30
As you can see, at the step to, the process and the thread don't have the same parameters. Is that normal?
#include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #include <pthread.h>
/* gcc schedparam.c -o schedparam -Wall -pthread */
int print_process_sched(pid_t pid) { struct sched_param param; int prio; int policy;
policy = sched_getscheduler(pid);
sched_getparam(pid,¶m); prio = param.sched_priority;
printf("Process %d : policy=%d prio=%d\n",(int)pid, policy,prio);
return 0; }
int utilities_print_thread_sched(pthread_t id) { struct sched_param param; int policy; int prio; unsigned long int lid = id;
if ( pthread_getschedparam(id, &policy, ¶m) ) { perror("pthread_getschedparam()"); return 1; }
prio = param.sched_priority;
printf("Thread %ld : policy=%d prio=%d\n", (long)lid, policy,prio);
return 0; }
int main(void ) {
struct sched_param p;
printf("1. "); print_process_sched(getpid()); printf("1. "); utilities_print_thread_sched(pthread_self());
p.sched_priority = 20; if ( sched_setscheduler(getpid(),SCHED_FIFO,&p) ) { perror("sched_setscheduler()"); return 1; }
printf("2. "); print_process_sched(getpid()); printf("2. "); utilities_print_thread_sched(pthread_self());
p.sched_priority = 30; if ( pthread_setschedparam(pthread_self(),SCHED_FIFO,&p) ) { perror("sched_setscheduler()"); return 1; }
printf("3. "); print_process_sched(getpid()); printf("3. "); utilities_print_thread_sched(pthread_self());
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