another? NFS deadlock on 9.2-PRERELEASE

[Daniel Braniss]

> 
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> On Tue, Aug 27, 2013 at 05:00:14PM +0300, Daniel Braniss wrote:
> > > Daniel Braniss wrote:
> > > > > Daniel Braniss wrote:
> > > > > > I upgraded our web server, and only after 3 hours it hung :-(
> > > > > > (as a side note, I have 2 other web servers, also running 9.2
> > > > > > doing
> > > > > > great :-)
> > > > > > go figure.
> > > > > >=20
> > > > > > anyways, in
> > > > > > 	ftp://ftp.cs.huji.ac.il/users/danny/freebsd/core.txt/0
> > > > > >=20
> > > > > > is the info after a forced panic.
> > > > > >=20
> > > > > Looks like the same hang to me. Several threads are sleeping on
> > > > > "pgrbwt"
> > > > > and lots are waiting for an NFS vnode lock.
> > > > >=20
> > > > > It should be fixed in RC3 (or revert r250907). If it still hangs
> > > > > with
> > > > > RC3 (or r250907 reverted), email again.
> > > > >=20
> > > > im following stable, hence it's till calling itself 9.2-PRERELEASE,
> > > > but
> > > > I did a sync this morning - local time, after rc3 was anounced.
> > > > but after 3.45 minutes is hung, data in
> > > > 	ftp://ftp.cs.huji.ac.il/users/danny/freebsd/core.txt/1
> > > >=20
> > > > I can't easely revert r250907, since i'm using mercuriall, but if
> > > > someone
> > > > can send me the pre r250907 files, i'll try.
> > > >=20
> > > r254947, which was committed to stable/9 a few hours ago is believed to
> > > fix the problem. Please update your stable/9 to post-r254947 and try it.
> > >=20
> > the current kernel has that fix (sys/kern/uipc_syscalls.c)
> > and if you check the core.txt/1 you will see no pgrbwt, only newnsf ...
> 
> There is almost no useful information in the core.txt/1.
> Provide the known data for the deadlock.

maybe the word deadlock is too strong, the host is diskless (one of many)
and so when NFS stops working/respondig, it hangs.
I will now make it dataless - the / will be from local disk, see if that
makes it easier to debug.