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From: Matt Jacob <mjacob@FreeBSD.org>
Date: Tue, 8 Jun 2010 22:40:03 +0000 (UTC)
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Subject: svn commit: r208927 - head/sys/geom
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Author: mjacob
Date: Tue Jun  8 22:40:02 2010
New Revision: 208927
URL: http://svn.freebsd.org/changeset/base/208927

Log:
  Try and narrow the gap in which you act on an event that has been canceled.
  Obtained from:	Jaako Heinonen
  MFC after:	1 month

Modified:
  head/sys/geom/geom_event.c

Modified: head/sys/geom/geom_event.c
==============================================================================
--- head/sys/geom/geom_event.c	Tue Jun  8 22:26:47 2010	(r208926)
+++ head/sys/geom/geom_event.c	Tue Jun  8 22:40:02 2010	(r208927)
@@ -76,6 +76,7 @@ struct g_event {
 #define EV_DONE		0x80000
 #define EV_WAKEUP	0x40000
 #define EV_CANCELED	0x20000
+#define EV_INPROGRESS	0x10000
 
 void
 g_waitidle(void)
@@ -206,12 +207,19 @@ one_event(void)
 		g_topology_unlock();
 		return (0);
 	}
+	if (ep->flag & EV_INPROGRESS) {
+		mtx_unlock(&g_eventlock);
+		g_topology_unlock();
+		return (1);
+	}
+	ep->flag |= EV_INPROGRESS;
 	mtx_unlock(&g_eventlock);
 	g_topology_assert();
 	ep->func(ep->arg, 0);
 	g_topology_assert();
 	mtx_lock(&g_eventlock);
 	TAILQ_REMOVE(&g_events, ep, events);
+	ep->flag &= ~EV_INPROGRESS;
 	mtx_unlock(&g_eventlock);
 	if (ep->flag & EV_WAKEUP) {
 		ep->flag |= EV_DONE;
@@ -255,6 +263,8 @@ g_cancel_event(void *ref)
 		break;
 	}
 	TAILQ_FOREACH_SAFE(ep, &g_events, events, epn) {
+		if (ep->flag & EV_INPROGRESS)
+			continue;
 		for (n = 0; n < G_N_EVENTREFS; n++) {
 			if (ep->ref[n] == NULL)
 				break;