X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=61aeee611a04da3c78083437bd6af48cbde8d366;hb=ab0aacbe1a25d50d069f0b24aa492e84ea296f57;hp=cf65992f4e57a8bc86187744271c5ee4c58b6d26;hpb=5161f31e09ce33dd79afad8d08a2372fbf1c4fbe;p=urcu.git

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index cf65992..61aeee6 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -48,12 +48,13 @@
 
 struct call_rcu_data {
 	/*
-	 * Align the tail on cache line size to eliminate false-sharing
-	 * with head.
+	 * We do not align head on a different cache-line than tail
+	 * mainly because call_rcu callback-invocation threads use
+	 * batching ("splice") to get an entire list of callbacks, which
+	 * effectively empties the queue, and requires to touch the tail
+	 * anyway.
 	 */
-	struct cds_wfcq_tail __attribute__((aligned(CAA_CACHE_LINE_SIZE))) cbs_tail;
-	/* Alignment on cache line size will add padding here */
-
+	struct cds_wfcq_tail cbs_tail;
 	struct cds_wfcq_head cbs_head;
 	unsigned long flags;
 	int32_t futex;
@@ -625,6 +626,10 @@ void call_rcu(struct rcu_head *head,
  * The caller must wait for a grace-period to pass between return from
  * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
  * previous call rcu data as argument.
+ *
+ * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
+ * a list corruption bug in the 0.7.x series. The equivalent fix
+ * appeared in 0.6.8 for the stable-0.6 branch.
  */
 void call_rcu_data_free(struct call_rcu_data *crdp)
 {