[PATCH] geom_bsd tasting holds topology_lock when doing I/O

[Ulf Lilleengen]

Hi,

I started having problems with gvinum hanging itself up because it was waiting
for the topology lock. At the same time geom_bsd was trying to taste the new
gvinum provider that I created. This resulted in a deadlock where gvinum waited
for the lock and g_bsd_taste waited for gvinum to finish a read BIO.

The patch also asserts that the lock is not held in g_bsd_taste

-- 
Ulf Lilleengen
-------------- next part --------------
Index: sys/geom/geom_bsd.c
===================================================================
RCS file: /home/ncvs/src/sys/geom/geom_bsd.c,v
retrieving revision 1.78
diff -u -r1.78 geom_bsd.c
--- sys/geom/geom_bsd.c	24 May 2006 11:02:32 -0000	1.78
+++ sys/geom/geom_bsd.c	27 Jul 2007 10:34:49 -0000
@@ -201,6 +201,8 @@
 	struct disklabel *dl;
 	off_t secoff;
 
+	g_topology_assert_not();
+
 	/*
 	 * We need to read entire aligned sectors, and we assume that the
 	 * disklabel does not span sectors, so one sector is enough.
@@ -502,6 +504,7 @@
 	 * using a simple "break".  This improves code clarity without
 	 * ending up in deep nesting and without using goto or come from.
 	 */
+	g_topology_unlock();
 	do {
 		/*
 		 * If the provider is an MBR we will only auto attach
@@ -571,8 +574,11 @@
 		 * Process the found disklabel, and modify our "slice"
 		 * instance to match it, if possible.
 		 */
+		g_topology_lock();
 		error = g_bsd_modify(gp, ms->label);
+		g_topology_unlock();
 	} while (0);
+	g_topology_lock();
 
 	/* Success or failure, we can close our provider now. */
 	g_access(cp, -1, 0, 0);