[Cc peter because he introduced this code]
Hi,
i was trying the following code in -current (basically copied from
vm_zeropage.c), to implement device polling in the idle loop, and
noticed that the process would take all of the CPU time. Being
suspicious that something was wrong with priorities, I added a
couple of printfs, and to my surprise, the priority of the process
(pri_level) after the first tsleep() becomes 104 instead of staying
at 255 as it was originally initialized.
A quick scan of the files in sys/sys shows that 104 is PPAUSE,
and this is the source of the problem.
I guess this is a bug in vm_zeropage.c, the second parameter
in tsleep should be td->td_ksegrp->kg_pri.pri_level instead
of PPAUSE, or at least the priority should be reset to the
original value after returning from the tsleep ?
cheers
luigi
static void
poll_idle(void)
{
struct thread *td = curthread;
struct rtprio rtp;
rtp.prio = RTP_PRIO_MAX; /* lowest priority */
rtp.type = RTP_PRIO_IDLE;
mtx_lock_spin(&sched_lock);
rtp_to_pri(&rtp, &td->td_ksegrp->kg_pri);
mtx_unlock_spin(&sched_lock);
printf("idlepoll start and sleep, pri is %d native %d user %d\n",
td->td_ksegrp->kg_pri.pri_level,
td->td_ksegrp->kg_pri.pri_native,
td->td_ksegrp->kg_pri.pri_user);
for (;;) {
if (poll_in_idle && poll_handlers > 0) {
idlepoll_sleeping = 0;
mtx_lock(&Giant);
ether_poll(poll_each_burst);
mtx_unlock(&Giant);
mtx_assert(&Giant, MA_NOTOWNED);
mtx_lock_spin(&sched_lock);
setrunqueue(td);
td->td_proc->p_stats->p_ru.ru_nvcsw++;
mi_switch();
mtx_unlock_spin(&sched_lock);
} else {
printf("idlepoll goes to sleep, "
"pri is %d native %d user %d\n",
td->td_ksegrp->kg_pri.pri_level,
td->td_ksegrp->kg_pri.pri_native,
td->td_ksegrp->kg_pri.pri_user);
idlepoll_sleeping = 1;
tsleep(&idlepoll_sleeping, PPAUSE, "pollid", hz * 3);
}
}
}
static struct proc *idlepoll;
static struct kproc_desc idlepoll_kp = {
"idlepoll",
poll_idle,
&idlepoll
};
SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &idlepoll_kp)
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