# HG changeset patch
# User Erik Quanstrom <quanstro@quanstro.net>
# Date 1331826884 -3600
# Node ID 3114b5af088bd60ecc17f00233c3b378141215d6
# Parent  9323f8fa6d56c87847052d79e05a0e44a329109b
port/chan.c: fix locking issue.

this was discovered as an occasional crash on plan 9 a few
years ago.  the problem is that the check is made outside
the lock.

change: reorganize as per charles comments.
change: make pretty, embiggen the diff with plan 9.

R=nixiedev, charles.forsyth, nemo.mbox
CC=nix-dev
http://codereview.appspot.com/5795071

Committer: Francisco J Ballesteros <nemo.mbox@gmail.com>

diff -r 9323f8fa6d56 -r 3114b5af088b sys/src/nix/port/chan.c
--- a/sys/src/nix/port/chan.c	Thu Mar 15 11:22:18 2012 +0100
+++ b/sys/src/nix/port/chan.c	Thu Mar 15 16:54:44 2012 +0100
@@ -922,14 +922,16 @@
 				 * mh->mount->to == c, so start at mh->mount->next
 				 */
 				rlock(&mh->lock);
-				for(f = mh->mount->next; f; f = f->next)
-					if((wq = ewalk(f->to, nil, names+nhave, ntry)) != nil)
-						break;
+				if(mh->mount){
+					for(f = mh->mount->next; f != nil; f = f->next){
+						if((wq = ewalk(f->to, nil, names+nhave, ntry)) != nil){
+							dc = f->to->dev->dc;
+							devno = f->to->devno;
+							break;
+						}
+					}
+				}
 				runlock(&mh->lock);
-				if(f != nil){
-					dc = f->to->dev->dc;
-					devno = f->to->devno;
-				}
 			}
 			if(wq == nil){
 				cclose(c);
@@ -1551,7 +1553,7 @@
 		goto Open;
 
 	default:
-		panic("unknown namec access %d\n", amode);
+		panic("unknown namec access %d", amode);
 	}
 
 	/* place final element in genbuf for e.g. exec */