Re: mount deadlock

[Andrew Doran <ad%netbsd.org@localhost>]

On Wed, Jan 09, 2008 at 02:03:05PM +0100, Tobias Nygren wrote:

> On Wed, 9 Jan 2008 13:19:30 +0200
> Antti Kantee <pooka%cs.hut.fi@localhost> wrote:
> 
> > On Wed Jan 09 2008 at 06:07:10 +0100, Tobias Nygren wrote:
> > > I have other filesystem related problems as well, for example mounting
> > > a filesystem onto a newly created directory tends to deadlock mount.
> > 
> > Hmm, sounds weird.  Is there a PR for this?  I couldn't repeat it with
> > a quick try.
> 
> No PR, but the machine is wedged as of this moment. I didn't bother
> rebooting it since it's nfsd is still happily serving up files.
> 
> Anything particular I could run from DDB to figure out why it's blocking
> infinitely on the buffer? This is sparc64 btw, and there are no other
> processes in unusual wait channels from what I can tell. They do get
> wedged if I try to access the vnode of the mount point.
> 
> db> trace/a 2742a340
> trace: pid 424 lid 1 at 0x275aee61
> sleepq_block(0, 0, 2742a340, 1, 55, 18a01e0) at netbsd:sleepq_block+0xfc
> cv_timedwait(18a3e50, 0, 0, 201b, 0, ffffffff80000000) at 
> netbsd:cv_timedwait+0xe8
> bbusy(605e490, 0, 0, 0, 0, ffffffff80000000) at netbsd:bbusy+0xac
> vinvalbuf(3751a420, 1, 605e490, 2742a340, 0, 0) at netbsd:vinvalbuf+0x11c
> do_sys_mount(16, 18147c0, 3f64240, ffffffffffffa620, ffffffff80000000, 
> fffffffff fffaa20) at netbsd:do_sys_mount+0x458
> sys___mount50(2742a340, 275afdc0, 275afe00, 1, 201c20, 1815de0) at 
> netbsd:sys___ mount50+0x28
> syscall_plain(275afed0, 5, 4063c7c4, 4063c7c8, 0, 275afdc0) at 
> netbsd:syscall_plain+0x118
> ?(101358, ffffffffffffa620, ffffffff80000000, ffffffffffffaa20,8, 0) at 
> 0x1008d78
> 
> Another recent mount issue is that mount -uw / no longer works in
> single user mode. This I can repeat on i386 as well. I must now specify
> the device name for this to succeed.

I noticed this yesterday and can reproduce it. Something is busying a buffer
and not releasing it later (eg by start I/O on it). I'll have a look.

Andrew