ifdef C, wait-free stack adaptative pop wait

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

diff --git a/urcu/rculfqueue.h b/urcu/rculfqueue.h
index b712998c07a929cfa5d49da370bd0c676c72ecdb..01c2092610350155247b87cadd6149aa3b26b4b1 100644 (file)
--- a/urcu/rculfqueue.h
+++ b/urcu/rculfqueue.h
@@ -26,6 +26,10 @@
 #include <urcu/urcu_ref.h>
 #include <assert.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
 #error "Dynamic loader LGPL wrappers not implemented yet"
 #endif
@@ -142,4 +146,8 @@ rcu_lfq_dequeue(struct rcu_lfq_queue *q, void (*release)(struct urcu_ref *))
        }
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _URCU_RCULFQUEUE_H */

diff --git a/urcu/rculfstack.h b/urcu/rculfstack.h
index a9e624ce792ee2b59ecb648084df5cda73a60e46..f80c7fea012a6e6240bf2ee04ee54f557966a4ff 100644 (file)
--- a/urcu/rculfstack.h
+++ b/urcu/rculfstack.h
@@ -23,6 +23,10 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
 #error "Dynamic loader LGPL wrappers not implemented yet"
 #endif
@@ -99,4 +103,8 @@ rcu_lfs_pop(struct rcu_lfs_stack *s)
        }
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _URCU_RCULFSTACK_H */

diff --git a/urcu/rcuwfqueue.h b/urcu/rcuwfqueue.h
index 857233b90b2f8c3d02b746f2508191b55cb62dc0..8c1d4a19c2ef573eaaf383952cca30c8b8138a3a 100644 (file)
--- a/urcu/rcuwfqueue.h
+++ b/urcu/rcuwfqueue.h
@@ -1,3 +1,6 @@
+#ifndef _URCU_RCUWFQUEUE_H
+#define _URCU_RCUWFQUEUE_H
+
 /*
  * rcuwfqueue.h
  *
@@ -23,6 +26,10 @@
 #include <urcu/urcu_ref.h>
 #include <assert.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
 #error "Dynamic loader LGPL wrappers not implemented yet"
 #endif
@@ -92,8 +99,10 @@ void rcu_wfq_enqueue(struct rcu_wfq_queue *q, struct rcu_wfq_node *node)
  * modified/re-used/freed until the reference count reaches zero and a grace
  * period has elapsed (after the refcount reached 0).
  *
- * TODO: implement adaptative busy-wait and wait/wakeup scheme rather than busy
- * loops. Better for UP.
+ * No need to go on a waitqueue here, as there is no possible state in which the
+ * list could cause dequeue to busy-loop needlessly while waiting for another
+ * thread to be scheduled. The queue appears empty until tail->next is set by
+ * enqueue.
  */
 struct rcu_wfq_node *
 rcu_wfq_dequeue_blocking(struct rcu_wfq_queue *q,
@@ -122,3 +131,9 @@ rcu_wfq_dequeue_blocking(struct rcu_wfq_queue *q,
                }
        }
 }
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_RCUWFQUEUE_H */

diff --git a/urcu/rcuwfstack.h b/urcu/rcuwfstack.h
index 300c95e3280b47c809b51a433d08844421f79525..71ecce8cce1c492f9ec48ccd90fb4c07ee1e5287 100644 (file)
--- a/urcu/rcuwfstack.h
+++ b/urcu/rcuwfstack.h
@@ -25,11 +25,19 @@
 
 #include <assert.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
 #error "Dynamic loader LGPL wrappers not implemented yet"
 #endif
 
 #define RCU_WF_STACK_END               ((void *)0x1UL)
+#define RCU_WFS_ADAPT_ATTEMPTS         10      /* Retry if being set */
+#define RCU_WFS_WAIT                   10      /* Wait 10 ms if being set */
+
+extern int rcu_wfs_futex;
 
 struct rcu_wfs_node {
        struct rcu_wfs_node *next;
@@ -78,13 +86,12 @@ void rcu_wfs_push(struct rcu_wfs_stack *s, struct rcu_wfs_node *node)
  * cmpxchg is protected from ABA races by holding a RCU read lock between
  * s->head read and cmpxchg modifying s->head and requiring that dequeuers wait
  * for a grace period before freeing the returned node.
- *
- * TODO: implement adaptative busy-wait and wait/wakeup scheme rather than busy
- * loops. Better for UP.
  */
 struct rcu_wfs_node *
 rcu_wfs_pop_blocking(struct rcu_wfs_stack *s)
 {
+       int attempt = 0;
+
        for (;;) {
                struct rcu_wfs_node *head;
 
@@ -96,6 +103,11 @@ rcu_wfs_pop_blocking(struct rcu_wfs_stack *s)
                        /* Retry while head is being set by push(). */
                        if (!next) {
                                rcu_read_unlock();
+                               if (++attempt >= RCU_WFS_ADAPT_ATTEMPTS) {
+                                       /* Sleep for 10ms */
+                                       poll(NULL, 0, RCU_WFS_WAIT);
+                                       attempt = 0;
+                               }
                                continue;
                        }
                        if (uatomic_cmpxchg(&s->head, head, next) == head) {
@@ -114,4 +126,8 @@ rcu_wfs_pop_blocking(struct rcu_wfs_stack *s)
        }
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _URCU_RCUWFSTACK_H */