Thanks a lot for all your help. I wanted to change the priority of
the RT task dynamically. I am currently not facing any problem changing
the priority of the RT task dynamically.
Thanks once again
Santhosh
On Wed, 16 Feb 2000 [EMAIL PROTECTED] wrote:
>
>
> On Wed, 16 Feb 2000, David Miller wrote:
>
> > > > Is there a way to change the priority of a thread which is
> > > > running. Is there any interface to change the attributes of an task
> > > > dynamically.
> > > [delete]
> > > self = pthread_self();
> > >
> > > // Get the current thread scheduling parameters.
> > > if(( r_c = pthread_getschedparam(self, &my_policy, &my_param)) != 0) {
> > > rt_printk("pthread_getschedparam error: %d\n", r_c);
> > > }
> > >
> > > // Set thread priority to the new value.
> > > my_param.sched_priority = NEW_PRIORITY;
> > > if(( r_c = pthread_setschedparam(self, my_policy, &my_param)) != 0) {
> > > rt_printk("pthread_setschedparam error: %d\n", r_c);
> > > }
> > >
> > >
> > NOTE: When you do this the results may not be what you would expect.
> > This can
> > raise or lower the priority but it will not prempt a lower priority
> > thread. In
> > other words. You set a thread to higher priority and it is waiting on
> > data to
> > be supplied by an interrupt. When the interrupt comes in the thread
> > will be made
> > ready and will execute before lower priority threads but it must wait
> > for the
> > currently running, possibly lower priority, thread to suspend.
> >
> > David Miller
> Your statement is true only for user level thread. In Linux, the kernel
> level thread will preempt the low priority thread immediately after the
> interrupt return except that the low priority thread is in kernel mode.
> In that case, the preemption will occur immediately after the low priority
> thread return to the user mode.
>
> Therefore, the latency depends on the execution time of system call. The
> preemption points of RED-Linux is used to reduce this delay. The low
> latency patch basicly do the same thing.
>
> Yu-Chung Wang
>
>
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