Date: Wed, 12 May 1999 19:51:32 -0700 (PDT) From: Cliff Skolnick <cliff@steam.com> To: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca> Cc: dg@root.com, Mike Tancsa <mike@sentex.net>, freebsd-stable@FreeBSD.ORG, luoqi@FreeBSD.ORG, Matthew Dillon <dillon@apollo.backplane.com> Subject: Re: vm_fault deadlock and PR 8416 ... NOT fixed! Message-ID: <Pine.BSF.4.10.9905121942190.40655-100000@lazlo.internal.steam.com> In-Reply-To: <199905121459.HAA27314@cwsys.cwsent.com>
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I've added "options DEBUG_LOCKS" to my kernel, and added the following code.
I'll post any interesting log messages that I see over the next day or so.
If I've done something terribly wrong that will hose my system, please email
me! Hacking locking code makes me a bit nervous.
Here's the diff to kern_lock.c I just added - someone in the know please
review this, and email if I need to add more instrumentation:
*** kern_lock.c-orig Tue May 11 22:53:19 1999
--- kern_lock.c Wed May 12 19:45:59 1999
***************
*** 229,236 ****
LK_WANT_UPGRADE
);
}
! if (error)
! break;
sharelock(lkp, 1);
COUNT(p, 1);
break;
--- 229,248 ----
LK_WANT_UPGRADE
);
}
!
! /* we will fall through and grant the lock after printing info */
! if (error) {
! if ((lkp->lk_flags & LK_SHARE_NONZERO) != 0 &&
! (flags & LK_CANRECURSE) != 0) {
! printf("deadlocktreat=%d, flags=0x%x\n",
! p->p_flag & P_DEADLKTREAT,
! extflags);
! lockmgr_printinfo(lkp);
! /* fall through to grant lock */
! } else {
! break;
! }
! }
sharelock(lkp, 1);
COUNT(p, 1);
break;
On Wed, 12 May 1999, Cy Schubert - ITSD Open Systems Group wrote:
> Would plan B risk corruption of any data? Could itself be the likely
> cause of any potential panics?
>
> Assuming plan B has no major risks, this might be a temporary
> workaround until we can wrap our minds around this one. It's just a
> rework of Luoqi's patch, just in case we want to try plan B again.
>
> --- kern_lock.c.orig Tue May 11 08:34:52 1999
> +++ kern_lock.c Wed May 12 05:38:52 1999
> @@ -215,7 +215,9 @@
> * lock itself ).
> */
> if (lkp->lk_lockholder != pid) {
> - if (p->p_flag & P_DEADLKTREAT) {
> + if ((p->p_flag & P_DEADLKTREAT) ||
> + ((lkp->lk_flags & LK_SHARE_NONZERO) != 0 &&
> + (flags & LK_CANRECURSE) != 0) {
> error = acquire(
> lkp,
> extflags,
>
> If this workaround doesn't work, then setting error = 0 and allowing
> the code to fall through to the subsequent sharelock may be our only
> choice for now.
>
> The other point I wish to make for all on this list is that Matt's
> patch fixes a read()/mmap() deadlock. It doesn't fix a write()/mmap()
> deadlock.
>
>
> Regards, Phone: (250)387-8437
> Cy Schubert Fax: (250)387-5766
> Open Systems Group Internet: Cy.Schubert@uumail.gov.bc.ca
> ITSD Cy.Schubert@gems8.gov.bc.ca
> Province of BC
> "e**(i*pi)+1=0"
>
> In message <199905120755.AAA01361@implode.root.com>, David Greenman
> writes:
> > >Well a few minutes ago my system went into deadlock - and this is with the
> > >kern_lock.c dated 5/11. This patch is different than the one in 8416 that
> > >solved my problem before. I'd say this the problem is still there.
> >
> > Time is very short for getting this fixed before the release deadline. I
> > think Luoqi's patch that was in the PR was suseptible to a priority inversion
> > problem and has risks associated with using it. The fix that Matt Dillion
> > made for -current that I back-ported to -stable was an attempt to fix the
> > problem while minimizing the side effects. If it doesn't fix the problem
> > then we'll proceed with plan B which is probably to just go with Luoqi's
> > fix or to possibly troubleshoot Matt's fix (but as I said, time is short).
> >
> > >Once again my server is useless, deadlocked. No panic, responding to pings,
> > >no ability to do disk I/O or any VM related stuff.
> > >
> > >An unhappy freebsd user once again,
> >
> > Is this really necessary? It sure doesn't help the debugging process.
> >
> > -DG
> >
> > David Greenman
> > Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
> > Creator of high-performance Internet servers - http://www.terasolutions.com
> >
> >
> > To Unsubscribe: send mail to majordomo@FreeBSD.org
> > with "unsubscribe freebsd-stable" in the body of the message
> >
>
>
>
>
> To Unsubscribe: send mail to majordomo@FreeBSD.org
> with "unsubscribe freebsd-stable" in the body of the message
>
--
Cliff Skolnick | "They that can give up essential liberty to obtain
Steam Tunnel Operations | a little temporary safety deserve neither liberty
cliff@steam.com | nor safety."
http://www.steam.com/ | -- Benjamin Franklin, 1759
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