Date: Mon, 26 Apr 2004 10:55:39 -0400 (EDT) From: Daniel Eischen <eischen@vigrid.com> To: David Xu <davidxu@freebsd.org> Cc: John Baldwin <jhb@freebsd.org> Subject: Re: kse_release and kse_wakeup problem (fwd) Message-ID: <Pine.GSO.4.10.10404261047480.19899-100000@pcnet5.pcnet.com> In-Reply-To: <408D0373.8050006@freebsd.org>
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On Mon, 26 Apr 2004, David Xu wrote:
> John Baldwin wrote:
> >
> >
> > I.e. do the upcall check in sleepq_catch_signals() right where you already do
> > thread_suspend_check(1). The only reason you have to do this, btw, is
> > because the kse_release() code is trying to mess with thread state internals
> > using sleepq_abort(), etc. The other in-kernel code that does that (signals)
> > already does the check in sleepq_catch_signals() and has done the same type
> > of check in msleep()/tsleep() for quite a while.
> >
> > If the kse_release() stuff was just using sleep/wakeup() rather than trying to
> > manually abort sleeps it wouldn't have to be so intimate with the sleep
> > interface.
> >
> > Note that thr's thr_wakeup() and thr_sleep() manage to simulate
> > synchronization w/o having to abort sleeps, but it is probably also easier to
> > do that than for the M:N case.
> >
>
> I think libthr will encounters same problem as libpthread with new sleep
> queue code, because mtx is released too early in msleep before thread
> markes itself as ON_SLEEPQ, thr_suspend and thr_wakeup have same race
> window as kse_release and kse_wakeup. Any code wants to put synchronous
> bit in td_flags like these codes will be broken.
I'm experimenting with adding an wakeup_thread() to kern_thread.c
(to complement wakeup() and wakeup_one()). If we shouldn't be
using sleepq's directly, the thread code either needs to
a) queue msleep()'ing upcalls/threads itself having them
all block on on their own unique wchan's; or
b) use a wakeup_thread() that wakes up a specific thread.
--
Dan Eischen
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