Thread priorities not working
 

Hi,

I am new to linux world.. I am creating a thread and setting the priority.

pthread_attr_t tAttr;

if (pthread_attr_init(&tAttr)==ENOMEM){
cout <<"Thread Attibute : No Memory left"<<endl;
}
if(pthread_attr_setdetachstate(&tAttr, PTHREAD_CREATE_DETACHED)!=0){
cout <<"Thread State: Error Making Detachable"<<endl;
}
struct sched_param schedParam;
pthread_t _taskId;

schedParam.sched_priority = 20;
int error = pthread_attr_setschedpolicy(&tAttr, SCHED_RR) ;
error = pthread_attr_setschedparam(&tAttr, &schedParam);
//cout << " pthread_attr_setschedparam Error = " << error << endl;
if(pthread_create(&_taskId, &tAttr, doCalculation , (void*)"Thread-20")!= 0){
cout<<" Task Creation : Resource Error , Permission Problem or Invalid Argument " <<endl;
return ;
}

//and checking the priority using following ...

int policy = 0;
if (pthread_getschedparam(_taskId, &policy, &schedParam) == 0) {
cout << "Thread sched policy = " << policy << " Prioriy = " << _schedParam.sched_priority <<endl;
}


But every time I get the output as
Thread sched policy = 0 Prioriy = 0.

Somehow priority is not getting set.. PLease help..

I am running this program on kernal 2.6.7-2.2. Fedora - 2.. Sticky bit is set

Please help. Let me know if I need to do any settings with the kernel.

Thanks and Regads
-- Ujjwal

Hey, the problem is that, by default the priority is 0 and the maximum and minimum priority is also 0 for pc based application. It range upto 200 for rtos.. for that we have to set CONFIG_MAX_RT_PRIO.
Unless you are doing specialized real-time programming with
kernel threads, the default is fine.

here is the link frm where i got the information
http://www.kernel.org/pub/linux/kern...e8-ac4-1.patch

hope this solves your problem...all the best