--- geom_event.c.orig	Sat Jan 10 22:00:13 2004
+++ geom_event.c	Sun Jan 11 15:52:00 2004
@@ -48,6 +48,7 @@
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <machine/stdarg.h>
+#include <machine/atomic.h>
 #include <sys/errno.h>
 #include <sys/time.h>
 #include <geom/geom.h>
@@ -309,6 +310,13 @@
 	va_list ap;
 	struct g_event *ep;
 	int error;
+#ifdef INVARIANTS
+	/*
+	 * This variable is used for deadlock prevention when we're waiting here
+	 * for function which is calling g_waitfor_event() function.
+	 */
+	static int waiting_for_function = 0;
+#endif
 
 	/* g_topology_assert_not(); */
 	KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
@@ -318,9 +326,14 @@
 	va_end(ap);
 	if (error)
 		return (error);
+	KASSERT(atomic_cmpset_int(&waiting_for_function, 0, 1) == 1,
+	    ("wait-for-event request called recursively"));
 	do 
 		tsleep(ep, PRIBIO, "g_waitfor_event", hz);
 	while (!(ep->flag & EV_DONE));
+#ifdef INVARIANTS
+	atomic_store_rel_int(&waiting_for_function, 0);
+#endif
 	if (ep->flag & EV_CANCELED)
 		error = EAGAIN;
 	g_free(ep);