From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@labs.coraid.com>
Date: Mon, 25 Oct 2010 09:20:51 -0400
To: lucio@proxima.alt.za, 9fans@9fans.net
Message-ID: <6701519c3b154bfb8462542b787fbae5@coraid.com>
In-Reply-To: <20101024122035.GB14331@fangle.proxima.alt.za>
References: <20101024122035.GB14331@fangle.proxima.alt.za>
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Subject: Re: [9fans] lock diagnostics on Fossil server
Topicbox-Message-UUID: 6c8249de-ead6-11e9-9d60-3106f5b1d025

> I had a couple of CPU sessions running on it.  The most obvious trigger
> seems to have been exportfs, I eventually turned off the stats report

sounds familiar.  this patch needs to be applied to the kernel:

/n/sources/plan9//sys/src/9/port/chan.c:1012,1018 - chan.c:1012,1020
  				/*
  				 * mh->mount->to == c, so start at mh->mount->next
  				 */
+ 				f = nil;
  				rlock(&mh->lock);
+ 				if(mh->mount)
  				for(f = mh->mount->next; f; f = f->next)
  					if((wq = ewalk(f->to, nil, names+nhave, ntry)) != nil)
  						break;

please apply.  if the problem persists after the fix, use acid to print the
source of the pcs and qpcs of the procs involved and send that offline.

- erik