Date: Thu, 23 Nov 2006 22:36:57 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Kostik Belousov" <kostikbel@gmail.com> Cc: freebsd-fs@freebsd.org, Mike Jakubik <mikej@rogers.com>, freebsd-stable@freebsd.org Subject: Re: md deadlocks on wdrain. Was: [Re: quota and snapshotsin6.1-RELEASE] Message-ID: <076f01c70f4f$e6b96050$b3db87d4@multiplay.co.uk> References: <447366AD.30203@rogers.com><20060701034922.GA37822@deviant.kiev.zoral.com.ua><027b01c70e6c$6c879470$b3db87d4@multiplay.co.uk> <20061123101246.GM1841@deviant.kiev.zoral.com.ua>
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Thanks for that, from our point of view its required
as without the machine deadlocks without even trying.
One real strange thing was that if I created a copy of
the vnode file, this particular task ( installworld )
would succeed but given the nature of the bug ( timing
critical ) that seem to make sence.
With this still being a potential issue I think we have
no choice but to migrate away from using any vnode backed
jails.
That said I thank you for this as it certainly help us.
Steve
----- Original Message -----
From: "Kostik Belousov" <kostikbel@gmail.com>
This is not a fix, this is only a way to make the deadlock less frequent
(I would not ever call it workaround). I have got a reports of deadlocks
with this change applied, and I think that I understand the cause of it.
Also, I have an idea of how to fix it, but not got around to even start
coding.
> ? sys/dev/md/.arch-ids
> Index: sys/dev/md/md.c
> ===================================================================
> RCS file: /usr/local/arch/ncvs/src/sys/dev/md/md.c,v
> retrieving revision 1.164
> diff -u -r1.164 md.c
> --- sys/dev/md/md.c 28 Mar 2006 21:25:11 -0000 1.164
> +++ sys/dev/md/md.c 1 Jul 2006 03:48:41 -0000
> @@ -650,6 +650,8 @@
> mtx_lock_spin(&sched_lock);
> sched_prio(curthread, PRIBIO);
> mtx_unlock_spin(&sched_lock);
> + if (sc->type == MD_VNODE)
> + curthread->td_pflags |= TDP_NORUNNINGBUF;
>
> for (;;) {
> mtx_lock(&sc->queue_mtx);
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