X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=ba6e02af27f3a18b60f26d56779bb5d4f869524e;hp=14733ab21e1b61d10bf93ecc082967cdf9d717cd;hb=ed868fa15f8c5511a1c32d1779f6fe37375c7137;hpb=90c1618acef5a848409867e9ff2dab7c8b859457

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 14733ab..ba6e02a 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -32,6 +32,7 @@
 #include <errno.h>
 #include <poll.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-qsbr.h"
@@ -41,20 +42,20 @@ 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;
+	unsigned long *rcu_reader_qs_gp;
 };
 
 #ifdef DEBUG_YIELD
@@ -105,11 +106,6 @@ static void force_mb_single_thread(struct reader_registry *index)
 }
 #endif /* #ifdef HAS_INCOHERENT_CACHES */
 
-static void force_mb_all_threads(void)
-{
-	smp_mb();
-}
-
 static void wait_for_quiescent_state(void)
 {
 	struct reader_registry *index;
@@ -121,8 +117,7 @@ static 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;
@@ -130,8 +125,7 @@ static 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;
@@ -145,12 +139,27 @@ static 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();
 }
 
 /*