panic: System call lstat returning with 1 locks held
attilio at freebsd.org
Wed Jan 30 07:07:18 PST 2008
2008/1/30, Yar Tikhiy <yar at comp.chem.msu.su>:
> On Tue, Jan 29, 2008 at 11:11:13PM +0100, Attilio Rao wrote:
> > I'm committing my WITNESS patch now to perforce so that other people
> > can hopefully stress-test it before to be committed.
> Do you think that that patch is applicable in my case? I.e., shall
> I use it to get more debug info on my panics?
> If so, where is the patched file in the depot?
Sorry but I had to delay the operation so far.
In the end, a suitable patch is located here:
I tried it and it alredy reported 4 LORs just when booting the kernel :)
So I would expect reasonably LOR cascades with this patch.
If you all 3 (Scot, Yar and Doug) could try and test it I would
appreciate a lot.
PS: This is the commit log to perforce:
Add WITNESS support to lockmgr.
A couple of notes:
- Two options have been added in order to serve WITNESS:
* LK_NOWITNESS which disables the support for the specified
* LK_NODUP which disallows the usual DUPOK behaviour
assumed as the default with lockmgr
- In the case of lockmgr_disown() the lock is simply dropped.
This means that a printout won't show the lock held even if it
is basically held by LK_KERNPROC
- In the case of upgrade we can have 3 different cases:
* The shared lock is unheld but consequent acquisition
fails; in this case the lock is reported dropped
* We are the first upgrader so there is an effective
* We are not the first upgrader so after the shared unlocking
we need to acquire the lock in exclusive mode; this will be
reported with 2 different WITNESS steps.
- In the case of LK_DRAIN the lock will be only checked about the
order but it won't be marked as acquired. This happens because a
drained lock is directly destroyed and not really released, so
witness_destroy() would badly panic in this case
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