X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=urcu.h;h=b6b5c7b039e359225d947afb91a29a2f25ba6a3c;hb=c265818b951224bcde407b1efa14f9daf44949b3;hp=bee7715270794c3e83cede4acb1741a98d361ac6;hpb=41718ff94c4a07cb5f56d68084267798e471d1b1;p=urcu.git

diff --git a/urcu.h b/urcu.h
index bee7715..b6b5c7b 100644
--- a/urcu.h
+++ b/urcu.h
@@ -1,6 +1,22 @@
 #ifndef _URCU_H
 #define _URCU_H
 
+/*
+ * urcu.h
+ *
+ * Userspace RCU header
+ *
+ * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * Credits for Paul e. McKenney <paulmck@linux.vnet.ibm.com>
+ * for inspiration coming from the Linux kernel RCU and rcu-preempt.
+ *
+ * The barrier, mb, rmb, wmb, atomic_inc, smp_read_barrier_depends, ACCESS_ONCE
+ * and rcu_dereference primitives come from the Linux kernel.
+ *
+ * Distributed under GPLv2
+ */
+
 /* The "volatile" is due to gcc bugs */
 #define barrier() __asm__ __volatile__("": : :"memory")
 
@@ -9,9 +25,6 @@
 #define rmb()   asm volatile("lfence":::"memory")
 #define wmb()   asm volatile("sfence" ::: "memory")
 
-
-
-/* x86 32 */
 static inline void atomic_inc(int *v)
 {
 	asm volatile("lock; incl %0"
@@ -64,39 +77,35 @@ static inline int get_urcu_qparity(void)
 }
 
 /*
- * returns urcu_parity.
+ * urcu_parity should be declared on the caller's stack.
  */
-static inline int rcu_read_lock(void)
+static inline void rcu_read_lock(int *urcu_parity)
 {
-	int urcu_parity = get_urcu_qparity();
-	urcu_active_readers[urcu_parity]++;
+	*urcu_parity = get_urcu_qparity();
+	urcu_active_readers[*urcu_parity]++;
 	/*
 	 * Increment active readers count before accessing the pointer.
 	 * See force_mb_all_threads().
 	 */
 	barrier();
-	return urcu_parity;
 }
 
-static inline void rcu_read_unlock(int urcu_parity)
+static inline void rcu_read_unlock(int *urcu_parity)
 {
 	barrier();
 	/*
 	 * Finish using rcu before decrementing the pointer.
 	 * See force_mb_all_threads().
 	 */
-	urcu_active_readers[urcu_parity]--;
+	urcu_active_readers[*urcu_parity]--;
 }
 
-extern void rcu_write_lock(void);
-extern void rcu_write_unlock(void);
-
 extern void *urcu_publish_content(void **ptr, void *new);
 
 /*
  * Reader thread registration.
  */
 extern void urcu_register_thread(void);
-extern void urcu_register_thread(void);
+extern void urcu_unregister_thread(void);
 
 #endif /* _URCU_H */