From 07050dc044cdca5a7cd51286840fb956c29a5f66 Mon Sep 17 00:00:00 2001
From: Samy Al Bahra <sbahra@repnop.org>
Date: Thu, 6 Sep 2012 12:21:27 -0400
Subject: [PATCH] ck_epoch: Short-circuit scan step if epoch was changed from
 underneath us.

---
 src/ck_epoch.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/ck_epoch.c b/src/ck_epoch.c
index 5fdac7e..4c14e05 100644
--- a/src/ck_epoch.c
+++ b/src/ck_epoch.c
@@ -329,8 +329,13 @@ ck_epoch_barrier(struct ck_epoch *global, struct ck_epoch_record *record)
 	 * could exist to the snapshot of e observed at the time this
 	 * function was called.
 	 */
-	while (cr = ck_epoch_scan(global, cr, delta), cr != NULL)
+	while (cr = ck_epoch_scan(global, cr, delta), cr != NULL) {
+		epoch = ck_pr_load_uint(&global->epoch);
+		if (epoch != delta)
+			break;
+
 		ck_pr_stall();
+	}
 
 	/*
 	 * As the synchronize operation is non-blocking, it is possible other