c - Issue with pthread_setschedparam, system hangs - 


static int pthrd_setthread_prio(int thred_prio) {     int                        thrd_policy = sched_rr;     struct sched_param         thr_prio;     int                        res=0;      thr_prio.sched_priority = thred_prio;      /* try setting thread/process priority via pthread */     res = pthread_setschedparam(  pthread_self(),                                   thrd_policy,                                  (const struct sched_param*) &thr_prio);      //pthread_setschedparam has 2 return values 0 on successs, >0 on failure     if(res != 0)     {        deb_err("pthread_setschedparam failed withe error %d\n",res);     }     res = pthread_getschedparam( pthread_self(),                                  &thrd_policy,                                 &thr_prio);     if(res < 0)     {        deb_err("pthread_getschedparam failed\n");     }      printf("thread policy %s priority %d process id %ld\n", \                    ( (thrd_policy == sched_fifo)  ? "sched_fifo" :                      (thrd_policy == sched_rr)    ? "sched_rr" :                      (thrd_policy == sched_other) ? "sched_other" : "???"),   thr_prio.sched_priority,   syscall(sys_gettid));      if ( (thr_prio.sched_priority != thred_prio) || (thrd_policy != sched_rr) )     {        deb_err("thread priority ==  %d, should %d error! using pthread\n",thr_prio.sched_priority ,thred_prio);        res=-1;     }      return (res); }

with above code used setting thread priority , creating thread-2 causing system hang @ point.

i established telnet session , used "ps -ef" command check real time priority of thread-2 , see set correctly. @ later stage causing system hang. confirmed removing particular function , assigned default priority thread.

could please let me know if missing here ?

you're setting realtime scheduling policy on thread. means higher priority realtime tasks can preempt it, if thread enters endless (or very-long-running) loop consuming cpu , not blocking, starve out other non-realtime tasks.

calculation-heavy threads don't block should not given realtime scheduling policy.


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