lfstack: relax constraints on node re-use

[urcu.git] / urcu / lfstack.h

diff --git a/urcu/lfstack.h b/urcu/lfstack.h
index 9f384d6b323b471bbeb96fb45d511038220e67c5..11a63d95cd3322a00c052a79080f1f93dd99e31c 100644 (file)
--- a/urcu/lfstack.h
+++ b/urcu/lfstack.h
@@ -84,10 +84,10 @@ struct cds_lfs_stack {
  * struct cds_lfs_stack and struct __cds_lfs_stack on any of those two
  * types.
  */
-typedef union __attribute__((__transparent_union__)) {
+typedef union {
        struct __cds_lfs_stack *_s;
        struct cds_lfs_stack *s;
-} cds_lfs_stack_ptr_t;
+} __attribute__((__transparent_union__)) cds_lfs_stack_ptr_t;
 
 #ifdef _LGPL_SOURCE
 
@@ -95,6 +95,7 @@ typedef union __attribute__((__transparent_union__)) {
 
 #define cds_lfs_node_init              _cds_lfs_node_init
 #define cds_lfs_init                   _cds_lfs_init
+#define __cds_lfs_init                 ___cds_lfs_init
 #define cds_lfs_empty                  _cds_lfs_empty
 #define cds_lfs_push                   _cds_lfs_push
 
@@ -177,9 +178,12 @@ extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
  * __cds_lfs_pop needs to be synchronized using one of the following
  * techniques:
  *
- * 1) Calling __cds_lfs_pop under rcu read lock critical section. The
- *    caller must wait for a grace period to pass before freeing the
- *    returned node or modifying the cds_lfs_node structure.
+ * 1) Calling __cds_lfs_pop under rcu read lock critical section.
+ *    Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
+ *    grace period to pass before freeing the returned node or pushing
+ *    the node back into the stack. It is valid to overwrite the content
+ *    of cds_lfs_node immediately after __cds_lfs_pop and
+ *    __cds_lfs_pop_all.
  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
  *    and __cds_lfs_pop_all callers.
  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
@@ -195,10 +199,12 @@ extern struct cds_lfs_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
  * matching the technique used to synchronize __cds_lfs_pop:
  *
  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
- *    both __cds_lfs_pop and cds_lfs_pop_all callers must wait for a
- *    grace period to pass before freeing the returned node or modifying
- *    the cds_lfs_node structure. However, no RCU read-side critical
- *    section is needed around __cds_lfs_pop_all.
+ *    both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
+ *    grace period to pass before freeing the returned node or pushing
+ *    the node back into the stack. It is valid to overwrite the content
+ *    of cds_lfs_node immediately after __cds_lfs_pop and
+ *    __cds_lfs_pop_all. No RCU read-side critical section is needed
+ *    around __cds_lfs_pop_all.
  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
  *    __cds_lfs_pop_all callers.
  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and