Subject: Re: 3.0_BETA I/O hang
To: Manuel Bouyer <bouyer@antioche.lip6.fr>
From: Bill Studenmund <wrstuden@netbsd.org>
List: tech-kern
Date: 04/14/2005 09:36:25
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On Thu, Apr 14, 2005 at 12:20:40PM +0200, Manuel Bouyer wrote:
>=20
> The mount point causing the problem is /domains. It contains only 2 large
> files (one 6GB, one 16GB). I was writing to the 16GB one (create, not
> overwrite) when this happended. The process creating the file is waiting =
on
> uvn_fp2:

I think that's the main culprit. I think the other nodes are all pilled up=
=20
on it in one way or another.

> mooney:/#ps axl |grep 17063
>   0 17063 12620   0 -18  0   80     4 uvn_fp2  DW+  ttyp2 3:34.89 /tmp/mk=
file
> Others are stuck on vnlock:
> mooney:/#ps axl | grep vnlock
>   0 21601 13819   0  -2  0   76     4 vnlock   DW+  ttyp3 0:00.01 ls -l=
=20
>   0 16715 15220   0  -2  0  936     4 vnlock   DW+  ttyp5 0:00.10 -csh (t=
csh)
>   0 21354 18277   0  -2  0   24     4 vnlock   DW   ttyp9 0:00.04 umount =
-f /do
>   0 21987 18277   0  -2  0   56     4 vnlock   DW   ttyp9 0:00.01 df -k=
=20
>=20
> I can read from /dev/raid2d without problems,
> so it's not the underlying device which is stuck. The box keeps running
> fine, expect accesses to /domains.
>=20
> Any idea what could cause this ? Anyone tried to create a file larger than
> 16GB already ? This filesystem uses has 32k block/4k fragment.

No, but I've seen this on occasion. For me, it happens when I'm getting a
crash dump of a multi-threaded app I'm working on. Sometimes crash dumps=20
tickle it, sometimes they don't. I have had days where every core works,=20
and days where every core does this.

The problem is that a page has been marked busy, and genfs_getpages is=20
waiting for it to unbusy. I expect that either we lost an unbusy, or we=20
somehow or another already have busied the pages and thus are deadlocked=20
on ourself.

Take care,

Bill

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