Re: Is a high witness refcount indicative of a missing unlock?

From: John Baldwin <jhb_at_freebsd.org>
Date: Mon, 06 Apr 2015 16:09:03 -0400
On Sunday, March 29, 2015 02:29:42 PM Lars wrote:
> Hi,
> I am poking around for a cause for my repeating deadlock issues on my system based on r 279869. ddb show witness show the “vnode interlock” and the “zfs” locks both with reference counts over 200K. Obviously they are related, and there is a find running (all the filesystems on this machine are zfs ( minus the specialty ones like devfs).
> 
> I don’t see any other withness entry with reference counts even in the ballpark of these two, so does this indicate that we have a vnode/zfs path were we don’t unlock?

The ref count just means that the locks exist (so you have 200k ZFS vnodes),
not that the locks are currently held.  The reference count on the witness
object is bumped when a lock is created that uses that witness object and
released when the lock is destroyed.

-- 
John Baldwin
Received on Mon Apr 06 2015 - 18:18:26 UTC

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