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Date:      Mon, 17 Aug 2009 23:19:46 +0200
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Sam Leffler <sam@errno.com>
Cc:        svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org
Subject:   Re: svn commit: r196293 - head/sys/kern
Message-ID:  <20090817211945.GC2298@garage.freebsd.pl>
In-Reply-To: <4A8978EC.101@errno.com>
References:  <200908170842.n7H8gYo5054777@svn.freebsd.org> <4A8978EC.101@errno.com>

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On Mon, Aug 17, 2009 at 08:36:12AM -0700, Sam Leffler wrote:
> Pawel Jakub Dawidek wrote:
> >Author: pjd
> >Date: Mon Aug 17 08:42:34 2009
> >New Revision: 196293
> >URL: http://svn.freebsd.org/changeset/base/196293
> >
> >Log:
> >  Because taskqueue_run() can drop tq_mutex, we need to check if the
> >  TQ_FLAGS_ACTIVE flag wasn't removed in the meantime, which means we=20
> >  missed a
> >  wakeup.
>=20
> So this would leave a task q thread running? [...]

Sleeping infinitely to be precise.

> [...] Can you describe the=20
> scenario that demonstrated this problem?

Once I moved ZFS from taskq ported from OpenSolaris to wrapper around
our taskqueue(9), the deadlock was easy to trigger (I experienced it by
testing with fsstress).

--=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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