Date: Mon, 7 Apr 2003 07:53:21 -0400 (EDT) From: Daniel Eischen <eischen@pcnet1.pcnet.com> To: Julian Elischer <julian@elischer.org> Cc: freebsd-threads@freebsd.org Subject: Re: PS_BLOCKED Message-ID: <Pine.GSO.4.10.10304070730480.9723-100000@pcnet1.pcnet.com> In-Reply-To: <Pine.BSF.4.21.0304062258430.55025-100000@InterJet.elischer.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, 6 Apr 2003, Julian Elischer wrote:
>
> On Sun, 6 Apr 2003, Daniel Eischen wrote:
>
> > On Sun, 6 Apr 2003, Julian Elischer wrote:
> > >
> > > If you have this behaviour, please make it an option. Possibly
> > > One way to do this would be to call kse_create, with the
> > > 'new-ksegrp' flag set but the mailbox pointer set to NULL.
> > >
> > > However why do you want to use kse_release for this.
> > > If you have only one thread in the KSEGRP then I'd call this
> > > "usleep()".
> >
> > It's so that the common code (called by both scope system
> > threads and scope process threads) can be the same. I don't
> > want to have to add checks all over the place to see if the
> > KSE is bound to a thread or not. Also, nanosleep doesn't
> > work well because you can't wake it up with a KSE mailbox
> > (kse_wakeup), plus there's a race condition if you try and
> > wake it up before it actually gets to the kernel to sleep.
> > The kse_wakeup() call is latched, so if it gets to the kernel
> > first, the next kse_release() will notice it.
>
> you cannot wake up a thread with no upcall mailbox using kse_wakeup
> because there is no thread mailbox address to match.
There is a kse mailbox, but no thread mailbox. I'm trying to
wakeup a KSE. What I do for multiple threaded KSEs is:
upcall_start(struct kse_mailbox *kse_mbox)
{
struct kse *curkse = (struct kse *)kse_mbx->km_udata;
check_completed(kse);
check_waitq(kse);
...
while ((td_run = runq_first(kse->k_kseg) == NULL) {
get_smallest_thread_wakeup_time(kse, &time_to_sleep);
kse->k_waiting = 1;
kse_release(&time_to_sleep)
}
/* switch to thread td_run */
}
Although, for multiple threaded KSEs, the "while" loop
only executes once because kse_release just causes another
upcall. If another KSE makes a thread runnable in the
first KSEs KSEG's runq, then it wakes up that KSE:
_thr_setrunnable(struct kse *curkse, struct pthread *thread)
{
SCHED_LOCK(curkse);
runq_insert(thread->kseg, thread);
SCHED_UNLOCK(curkse);
if ((thread->kse->k_kseg != curkse->k_kseg) &&
(thread->kse->k_waiting != 0)) {
thread->kse->k_waiting = 0;
kse_wakeup(&thread->kse->k_mbox);
}
}
or something like that.
For a single threaded KSE/KSEG, I don't want the upcall but I
still want to use kse_release(). I need to be able to wakeup
that KSE so that it may continue it's thread (it could be the
thread was in pthread_cond_wait() and it was signalled by
a thread in another KSE). And I don't want upcalls on this
KSE because there is only one thread; I don't want the overhead
of the upcall and its stack. And in order to prevent upcalls,
I have to make sure the kse mailbox has NULL in km_curthread.
That's the solution I'm looking for. I think kse_wakeup()
should be tweakable so that I don't get an upcall.
--
Dan Eischen
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.GSO.4.10.10304070730480.9723-100000>