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Date:      Tue, 7 Nov 2006 20:48:12 +0100
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        John Baldwin <jhb@freebsd.org>
Cc:        alc@freebsd.org, freebsd-current@freebsd.org, tegge@freebsd.org
Subject:   Re: VM deadlock?
Message-ID:  <20061107194812.GA25603@garage.freebsd.pl>
In-Reply-To: <200611071324.23525.jhb@freebsd.org>
References:  <20061105152417.GM83118@garage.freebsd.pl> <200611071324.23525.jhb@freebsd.org>

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On Tue, Nov 07, 2006 at 01:24:22PM -0500, John Baldwin wrote:
> On Sunday 05 November 2006 10:24, Pawel Jakub Dawidek wrote:
> > db> sh allchain
> > chain 1:
> >  thread 100260 (pid 90346, qmail-smtpd) blocked on lock 0xc07177e0 (sle=
ep=20
> mutex) "Giant"
> >  thread 100133 (pid 89997, qmail-smtpd) blocked on lock 0xc0722700 (sle=
ep=20
> mutex) "vm page queue mutex"
> >  thread 100105 (pid 4315, drwebd) is on a run queue
> > chain 2:
> >  thread 100098 (pid 4316, qmail-smtpd) blocked on lock 0xc0722700 (slee=
p=20
> mutex) "vm page queue mutex"
> >  thread 100105 (pid 4315, drwebd) is on a run queue
> > chain 3:
> >  thread 100031 (pid 34, pagezero) blocked on lock 0xc0722700 (sleep=20
> mutex) "vm page queue mutex"
> >  thread 100105 (pid 4315, drwebd) is on a run queue
> > chain 4:
> >  thread 100015 (pid 3, g_up) blocked on lock 0xc0722700 (sleep mutex) "=
vm=20
> page queue mutex"
> >  thread 100105 (pid 4315, drwebd) is on a run queue
> > chain 5:
> >  thread 100002 (pid 14, swi4: clock sio) blocked on lock 0xc072146c (sl=
eep=20
> mutex) "tcp"
> >  thread 100000 (pid 16, swi1: net) blocked on lock 0xc0722700 (sleep=20
> mutex) "vm page queue mutex"
> >  thread 100105 (pid 4315, drwebd) is on a run queue
> > db> sh locktree
> > db> sh turnstile
> >=20
> > Process drwebd (pid 4315) doesn't seem to go any further.
>=20
> How about 'show allpcpu' to see which threads are running?

I get some feedback from tegge@ and kib@ is willing to investigate it
further. This looks more like scheduler issue, not VM issue.

There are 4 CPUs. 3 are idle, one is stuck running userland process at
this point.

Disabling PREEMPTION seemed to help.

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

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