wfstack: implement mutex-free wfstack with transparent union

[urcu.git] / urcu / wfstack.h

diff --git a/urcu/wfstack.h b/urcu/wfstack.h
index fc0b44b791fcf218c56714711e235cc40465296f..b914f41e6cfdd17e42648ef0867bf92b4526da1c 100644 (file)
--- a/urcu/wfstack.h
+++ b/urcu/wfstack.h
@@ -83,11 +83,25 @@ struct cds_wfs_head {
        struct cds_wfs_node node;
 };
 
+struct __cds_wfs_stack {
+       struct cds_wfs_head *head;
+};
+
 struct cds_wfs_stack {
        struct cds_wfs_head *head;
        pthread_mutex_t lock;
 };
 
+/*
+ * The transparent union allows calling functions that work on both
+ * struct cds_wfs_stack and struct __cds_wfs_stack on any of those two
+ * types.
+ */
+typedef union __attribute__((__transparent_union__)) {
+       struct __cds_wfs_stack *_s;
+       struct cds_wfs_stack *s;
+} cds_wfs_stack_ptr_t;
+
 #ifdef _LGPL_SOURCE
 
 #include <urcu/static/wfstack.h>
@@ -135,12 +149,17 @@ extern void cds_wfs_node_init(struct cds_wfs_node *node);
  */
 extern void cds_wfs_init(struct cds_wfs_stack *s);
 
+/*
+ * __cds_wfs_init: initialize wait-free stack.
+ */
+extern void __cds_wfs_init(struct __cds_wfs_stack *s);
+
 /*
  * cds_wfs_empty: return whether wait-free stack is empty.
  *
  * No memory barrier is issued. No mutual exclusion is required.
  */
-extern bool cds_wfs_empty(struct cds_wfs_stack *s);
+extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack);
 
 /*
  * cds_wfs_push: push a node into the stack.
@@ -151,7 +170,7 @@ extern bool cds_wfs_empty(struct cds_wfs_stack *s);
  * Returns 0 if the stack was empty prior to adding the node.
  * Returns non-zero otherwise.
  */
-extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
+extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
 
 /*
  * cds_wfs_pop_blocking: pop a node from the stack.