Date: Mon, 7 Jul 2003 19:25:27 +1000 From: Tim Robbins <tjr@FreeBSD.ORG> To: "Marc G. Fournier" <scrappy@hub.org>, freebsd-stable@freebsd.org, Ted Mittelstaedt <tedm@toybox.placo.com> Subject: Re: Okay, looks like I might have a *good* one here ... inode hang Message-ID: <20030707192527.A9706@dilbert.robbins.dropbear.id.au> In-Reply-To: <20030707080530.GA23029@HAL9000.homeunix.com>; from das@freebsd.org on Mon, Jul 07, 2003 at 01:05:30AM -0700 References: <20030701155450.J67063@hub.org> <20030702073306.GA3324@HAL9000.homeunix.com> <20030702084558.J67063@hub.org> <20030703033117.GA7647@HAL9000.homeunix.com> <20030703005047.B67063@hub.org> <20030707080530.GA23029@HAL9000.homeunix.com>
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On Mon, Jul 07, 2003 at 01:05:30AM -0700, David Schultz wrote: > On Thu, Jul 03, 2003, Marc G. Fournier wrote: > > > follow that one, too. Maybe the trail will simply lead back to > > > unionfs... > > > > 'K, how about a loop? > > Heh...it's a deadlock between unionfs and nullfs. Sheesh. > If unionfs is at fault here, I think I already know where > the problem is, and it isn't easy to fix. But I'll have to > look more carefully when I get a chance. nullfs on 4.x can probably deadlock in certain situations while attempting to recycle vnodes; see null_vnops.c 1.63. This bug was made more obvious in 5.x by null_vnops.c 1.51, but I'm pretty sure that the problem was still there in earlier versions, but was just harder to trigger. There are a few questionable things in unionfs too. There might be a race in union_inactive() (should it grab the vnode interlock before dropping the vnode lock and call vgonel() instead of vgone()?), and the support for locking stacks of vnodes seems to be #if 0'd out in union_lock(). Tim
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