X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=61aeee611a04da3c78083437bd6af48cbde8d366;hb=d89ec7629b8cafdc12e619cf5f07ceb5b0279275;hp=dca98e4ae073d45f93d8665235b715661f16c0ad;hpb=b9f893b69fbc31baea418794938f4eb74cc4923a;p=urcu.git

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index dca98e4..61aeee6 100644
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -48,15 +48,14 @@
 
 struct call_rcu_data {
 	/*
-	 * Align the tail on cache line size to eliminate false-sharing
-	 * with head. Small note, however: the "qlen" field, kept for
-	 * debugging, will cause false-sharing between enqueue and
-	 * dequeue.
+	 * 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 cbs_tail;
-	/* Alignment on cache line size will add padding here */
-
-	struct cds_wfcq_head __attribute__((aligned(CAA_CACHE_LINE_SIZE))) cbs_head;
+	struct cds_wfcq_head cbs_head;
 	unsigned long flags;
 	int32_t futex;
 	unsigned long qlen; /* maintained for debugging. */
@@ -627,6 +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)
 {