Category: geom

Index: sys/geom/zero/g_zero.c
===================================================================
--- sys/geom/zero/g_zero.c	(revision 186191)
+++ sys/geom/zero/g_zero.c	(working copy)
@@ -104,7 +104,7 @@ g_zero_destroy_geom(struct gctl_req *req
 	if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
 		return (EBUSY);
 	g_wither_geom(gp, ENXIO);
-	return (EBUSY);
+	return (0);
 }
 
 static struct g_class g_zero_class = {
Index: sys/geom/geom_subr.c
===================================================================
--- sys/geom/geom_subr.c	(revision 186191)
+++ sys/geom/geom_subr.c	(working copy)
@@ -135,7 +135,7 @@ g_unload_class(void *arg, int flag)
 {
 	struct g_hh00 *hh;
 	struct g_class *mp;
-	struct g_geom *gp;
+	struct g_geom *gp, *gp2;
 	struct g_provider *pp;
 	struct g_consumer *cp;
 	int error;
@@ -146,15 +146,6 @@ g_unload_class(void *arg, int flag)
 	G_VALID_CLASS(mp);
 	g_trace(G_T_TOPOLOGY, "g_unload_class(%s)", mp->name);
 
-	/*
-	 * We allow unloading if we have no geoms, or a class
-	 * method we can use to get rid of them.
-	 */
-	if (!LIST_EMPTY(&mp->geom) && mp->destroy_geom == NULL) {
-		hh->error = EOPNOTSUPP;
-		return;
-	}
-
 	/* We refuse to unload if anything is open */
 	LIST_FOREACH(gp, &mp->geom, geom) {
 		LIST_FOREACH(pp, &gp->provider, provider)
@@ -167,6 +158,24 @@ g_unload_class(void *arg, int flag)
 				hh->error = EBUSY;
 				return;
 			}
+		/*
+		 * Check if there is unfinished withering pending. We are
+		 * likely in the event thread and can't get the work done
+		 * right now.
+		 */
+		if (gp->flags & G_GEOM_WITHER) {
+			hh->error = EDEADLK;
+			return;
+		}
+	}
+
+	/*
+	 * We allow unloading if we have no geoms, or a class
+	 * method we can use to get rid of them.
+	 */
+	if (!LIST_EMPTY(&mp->geom) && mp->destroy_geom == NULL) {
+		hh->error = EOPNOTSUPP;
+		return;
 	}
 
 	/* Bar new entries */
@@ -174,13 +183,25 @@ g_unload_class(void *arg, int flag)
 	mp->config = NULL;
 
 	error = 0;
+	gp2 = NULL;
 	for (;;) {
 		gp = LIST_FIRST(&mp->geom);
 		if (gp == NULL)
 			break;
+		/*
+		 * Break the loop if the geom was not destroyed.
+		 * Many classes use withering in their destroy method
+		 * but withering is unable to proceed now because we are
+		 * blocking the event thread.
+		 */
+		if (gp == gp2) {
+			error = EDEADLK;
+			break;
+		}
 		error = mp->destroy_geom(NULL, mp, gp);
 		if (error != 0)
 			break;
+		gp2 = gp;
 	}
 	if (error == 0) {
 		if (mp->fini != NULL)
@@ -233,9 +254,12 @@ g_modevent(module_t mod, int type, void 
 		break;
 	case MOD_UNLOAD:
 		g_trace(G_T_TOPOLOGY, "g_modevent(%s, UNLOAD)", hh->mp->name);
-		error = g_waitfor_event(g_unload_class, hh, M_WAITOK, NULL);
-		if (error == 0)
-			error = hh->error;
+		do {
+			error = g_waitfor_event(g_unload_class, hh, M_WAITOK,
+			    NULL);
+			if (error == 0)
+				error = hh->error;
+		} while (error == EDEADLK);
 		if (error == 0) {
 			KASSERT(LIST_EMPTY(&hh->mp->geom),
 			    ("Unloaded class (%s) still has geom", hh->mp->name));