On Wed, 24 Jan 2007, David Xu wrote:
Jeff Roberson wrote:
if idlethread is preempted, who will clear its idle bit in idle_cpus_mask
?
idle_cpus_mask was broken before for all schedulers. This commit didn't
change that. ULE doesn't use idle_cpus_mask and it's idlethread doesn't
set or clear it. The idle thread for the other schedulers remains
unchanged.
I havn't read ULE code, but 4BSD has following code:
This is the very same code that was there before. I didn't change it. I
just moved it into the schedulers. It was always broken with preemption.
I tried to use idle_cpus_mask in ULE but found that it always was set for
most CPUs. You will find that IPI_PREEMPT also had no effect but I fixed
that recently.
Jeff
void
sched_idletd(void *dummy)
{
struct proc *p;
struct thread *td;
#ifdef SMP
cpumask_t mycpu;
#endif
td = curthread;
p = td->td_proc;
#ifdef SMP
mycpu = PCPU_GET(cpumask);
mtx_lock_spin(&sched_lock);
idle_cpus_mask |= mycpu;
mtx_unlock_spin(&sched_lock);
#endif
for (;;) {
mtx_assert(&Giant, MA_NOTOWNED);
how about if the idlethread is preempted here ? mycpu is not cleared.
while (sched_runnable() == 0)
cpu_idle();
mtx_lock_spin(&sched_lock);
#ifdef SMP
idle_cpus_mask &= ~mycpu;
#endif
mi_switch(SW_VOL, NULL);
#ifdef SMP
idle_cpus_mask |= mycpu;
#endif
mtx_unlock_spin(&sched_lock);
}
}
Julian wants to set idle_cpus_mask in sched_switch() which would make it
accurate no matter how idlethread switched out. that seems much more
reasonable to me.
I haven't seen sched_switch clears it, so at least, it should be fixed for
current 4BSD scheduler.
Cheers,
Jeff
Regards,
David Xu
_______________________________________________
[email protected] mailing list
http://lists.freebsd.org/mailman/listinfo/cvs-all
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
