X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=ba6e02af27f3a18b60f26d56779bb5d4f869524e;hp=878a550b9291d21a464f5e4c1db9e58f1d741ea3;hb=a669219f71cabe41a5832bdda98c94e4ad63e529;hpb=332c334642672c5cf5e437f5ab2457ce6cddc21a

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 878a550..ba6e02a 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -1,7 +1,7 @@
 /*
- * urcu.c
+ * urcu-qsbr.c
  *
- * Userspace RCU library
+ * Userspace RCU QSBR library
  *
  * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
@@ -32,30 +32,30 @@
 #include <errno.h>
 #include <poll.h>
 
-#include "urcu-qsbr.h"
+#define BUILD_QSBR_LIB
+#include "urcu-qsbr-static.h"
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
-//#include "urcu.h"
+#include "urcu-qsbr.h"
 
 pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /*
  * Global grace period counter.
  */
-long urcu_gp_ctr = 0;
+unsigned long urcu_gp_ctr = RCU_GP_ONLINE;
 
 /*
  * Written to only by each individual reader. Read by both the reader and the
  * writers.
  */
-long __thread rcu_reader_qs_gp;
+unsigned long __thread rcu_reader_qs_gp;
 
 /* Thread IDs of registered readers */
 #define INIT_NUM_THREADS 4
 
 struct reader_registry {
 	pthread_t tid;
-	long *rcu_reader_qs_gp;
-	char *need_mb;
+	unsigned long *rcu_reader_qs_gp;
 };
 
 #ifdef DEBUG_YIELD
@@ -64,10 +64,9 @@ unsigned int __thread rand_yield;
 #endif
 
 static struct reader_registry *registry;
-static char __thread need_mb;
 static int num_readers, alloc_readers;
 
-void internal_urcu_lock(void)
+static void internal_urcu_lock(void)
 {
 	int ret;
 
@@ -84,17 +83,12 @@ void internal_urcu_lock(void)
 			perror("Error in pthread mutex lock");
 			exit(-1);
 		}
-		if (need_mb) {
-			smp_mb();
-			need_mb = 0;
-			smp_mb();
-		}
 		poll(NULL,0,10);
 	}
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
 }
 
-void internal_urcu_unlock(void)
+static void internal_urcu_unlock(void)
 {
 	int ret;
 
@@ -112,12 +106,7 @@ static void force_mb_single_thread(struct reader_registry *index)
 }
 #endif /* #ifdef HAS_INCOHERENT_CACHES */
 
-static void force_mb_all_threads(void)
-{
-	smp_mb();
-}
-
-void wait_for_quiescent_state(void)
+static void wait_for_quiescent_state(void)
 {
 	struct reader_registry *index;
 
@@ -128,8 +117,7 @@ void wait_for_quiescent_state(void)
 	 */
 	for (index = registry; index < registry + num_readers; index++) {
 #ifndef HAS_INCOHERENT_CACHES
-		while (rcu_gp_ongoing(index->rcu_reader_qs_gp) &&
-		       (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0))
+		while (rcu_gp_ongoing(index->rcu_reader_qs_gp))
 			cpu_relax();
 #else /* #ifndef HAS_INCOHERENT_CACHES */
 		int wait_loops = 0;
@@ -137,8 +125,7 @@ void wait_for_quiescent_state(void)
 		 * BUSY-LOOP. Force the reader thread to commit its
 		 * rcu_reader_qs_gp update to memory if we wait for too long.
 		 */
-		while (rcu_gp_ongoing(index->rcu_reader_qs_gp) &&
-		       (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0)) {
+		while (rcu_gp_ongoing(index->rcu_reader_qs_gp)) {
 			if (wait_loops++ == KICK_READER_LOOPS) {
 				force_mb_single_thread(index);
 				wait_loops = 0;
@@ -152,12 +139,27 @@ void wait_for_quiescent_state(void)
 
 void synchronize_rcu(void)
 {
+	unsigned long was_online;
+
+	was_online = rcu_reader_qs_gp;
+
+	/*
+	 * Mark the writer thread offline to make sure we don't wait for
+	 * our own quiescent state. This allows using synchronize_rcu() in
+	 * threads registered as readers.
+	 */
+	smp_mb();
+	if (was_online)
+		STORE_SHARED(rcu_reader_qs_gp, 0);
+
 	internal_urcu_lock();
-	force_mb_all_threads();
-	urcu_gp_ctr += 2;
+	STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr + RCU_GP_CTR);
 	wait_for_quiescent_state();
-	force_mb_all_threads();
 	internal_urcu_unlock();
+
+	if (was_online)
+		_STORE_SHARED(rcu_reader_qs_gp, LOAD_SHARED(urcu_gp_ctr));
+	smp_mb();
 }
 
 /*
@@ -200,6 +202,21 @@ void *rcu_publish_content_sym(void **p, void *v)
 	return oldptr;
 }
 
+void rcu_quiescent_state(void)
+{
+	_rcu_quiescent_state();
+}
+
+void rcu_thread_offline(void)
+{
+	_rcu_thread_offline();
+}
+
+void rcu_thread_online(void)
+{
+	_rcu_thread_online();
+}
+
 static void rcu_add_reader(pthread_t id)
 {
 	struct reader_registry *oldarray;
@@ -222,7 +239,6 @@ static void rcu_add_reader(pthread_t id)
 	registry[num_readers].tid = id;
 	/* reference to the TLS of _this_ reader thread. */
 	registry[num_readers].rcu_reader_qs_gp = &rcu_reader_qs_gp;
-	registry[num_readers].need_mb = &need_mb;
 	num_readers++;
 }
 
@@ -251,10 +267,10 @@ static void rcu_remove_reader(pthread_t id)
 
 void rcu_register_thread(void)
 {
-	_rcu_thread_online();
 	internal_urcu_lock();
 	rcu_add_reader(pthread_self());
 	internal_urcu_unlock();
+	_rcu_thread_online();
 }
 
 void rcu_unregister_thread(void)