From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 1 Sep 2011 13:28:30 +0000 (-0400)
Subject: Make lf stack push return if the stack was empty
X-Git-Tag: v0.6.5~41
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=e1a3b81e201ccfd019dae3778bd6ba0bd1e545e4;p=userspace-rcu.git

Make lf stack push return if the stack was empty

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/rculfstack.c b/rculfstack.c
index aa906af..f58628c 100644
--- a/rculfstack.c
+++ b/rculfstack.c
@@ -51,9 +51,10 @@ void cds_lfs_init_rcu(struct cds_lfs_stack_rcu *s)
 	_cds_lfs_init_rcu(s);
 }
 
-void cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s, struct cds_lfs_node_rcu *node)
+int cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s,
+		struct cds_lfs_node_rcu *node)
 {
-	_cds_lfs_push_rcu(s, node);
+	return _cds_lfs_push_rcu(s, node);
 }
 
 struct cds_lfs_node_rcu *cds_lfs_pop_rcu(struct cds_lfs_stack_rcu *s)
diff --git a/urcu/rculfstack.h b/urcu/rculfstack.h
index f673952..cf00daf 100644
--- a/urcu/rculfstack.h
+++ b/urcu/rculfstack.h
@@ -68,7 +68,8 @@ struct cds_lfs_stack_rcu {
 
 extern void cds_lfs_node_init_rcu(struct cds_lfs_node_rcu *node);
 extern void cds_lfs_init_rcu(struct cds_lfs_stack_rcu *s);
-extern void cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s, struct cds_lfs_node_rcu *node);
+extern int cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s,
+			struct cds_lfs_node_rcu *node);
 
 /*
  * Acts as a RCU reader.
diff --git a/urcu/static/rculfstack.h b/urcu/static/rculfstack.h
index 9d69fa7..1df121b 100644
--- a/urcu/static/rculfstack.h
+++ b/urcu/static/rculfstack.h
@@ -64,9 +64,13 @@ void _cds_lfs_init_rcu(struct cds_lfs_stack_rcu *s)
  * required if we first read the old head value). This design decision
  * might be revisited after more throrough benchmarking on various
  * platforms.
+ *
+ * Returns 0 if the stack was empty prior to adding the node.
+ * Returns non-zero otherwise.
  */
 static inline
-void _cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s, struct cds_lfs_node_rcu *node)
+int _cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s,
+			  struct cds_lfs_node_rcu *node)
 {
 	struct cds_lfs_node_rcu *head = NULL;
 
@@ -82,6 +86,7 @@ void _cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s, struct cds_lfs_node_rcu *nod
 		if (old_head == head)
 			break;
 	}
+	return (int) !!((unsigned long) head);
 }
 
 /*