X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu-qsbr.c;h=d1f5d91846af8f8098eacab85a588d945ab9873f;hb=256dd999d11736ebe5ad2865219879199c89cc90;hp=48bc62ec25e09e18395970d591f9dc64b57a1ed7;hpb=656c6da75f7ee119bfc49e026f52d695d0d1aea2;p=urcu.git

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 48bc62e..d1f5d91 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.
@@ -32,9 +32,9 @@
 #include <errno.h>
 #include <poll.h>
 
-#include "urcu-static.h"
+#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;
 
@@ -47,15 +47,14 @@ long urcu_gp_ctr = 0;
  * Written to only by each individual reader. Read by both the reader and the
  * writers.
  */
-long __thread urcu_active_readers;
+long __thread rcu_reader_qs_gp;
 
 /* Thread IDs of registered readers */
 #define INIT_NUM_THREADS 4
 
 struct reader_registry {
 	pthread_t tid;
-	long *urcu_active_readers;
-	char *need_mb;
+	long *rcu_reader_qs_gp;
 };
 
 #ifdef DEBUG_YIELD
@@ -64,10 +63,9 @@ 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 +82,12 @@ 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;
 
@@ -117,26 +110,28 @@ 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;
 
 	if (!registry)
 		return;
 	/*
-	 * Wait for each thread urcu_active_readers count to become 0.
+	 * Wait for each thread rcu_reader_qs_gp count to become 0.
 	 */
 	for (index = registry; index < registry + num_readers; index++) {
 #ifndef HAS_INCOHERENT_CACHES
-		while (rcu_old_gp_ongoing(index->urcu_active_readers))
+		while (rcu_gp_ongoing(index->rcu_reader_qs_gp) &&
+		       (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0))
 			cpu_relax();
 #else /* #ifndef HAS_INCOHERENT_CACHES */
 		int wait_loops = 0;
 		/*
 		 * BUSY-LOOP. Force the reader thread to commit its
-		 * urcu_active_readers update to memory if we wait for too long.
+		 * rcu_reader_qs_gp update to memory if we wait for too long.
 		 */
-		while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
+		while (rcu_gp_ongoing(index->rcu_reader_qs_gp) &&
+		       (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0)) {
 			if (wait_loops++ == KICK_READER_LOOPS) {
 				force_mb_single_thread(index);
 				wait_loops = 0;
@@ -150,12 +145,27 @@ void wait_for_quiescent_state(void)
 
 void synchronize_rcu(void)
 {
+	int was_online;
+
+	was_online = rcu_reader_qs_gp & 1;
+
+	/*
+	 * 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.
+	 */
+	if (was_online)
+		_rcu_thread_offline();
+
 	internal_urcu_lock();
 	force_mb_all_threads();
 	urcu_gp_ctr += 2;
 	wait_for_quiescent_state();
 	force_mb_all_threads();
 	internal_urcu_unlock();
+
+	if (was_online)
+		_rcu_thread_online();
 }
 
 /*
@@ -198,6 +208,21 @@ 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;
@@ -219,8 +244,7 @@ static void rcu_add_reader(pthread_t id)
 	}
 	registry[num_readers].tid = id;
 	/* reference to the TLS of _this_ reader thread. */
-	registry[num_readers].urcu_active_readers = &urcu_active_readers;
-	registry[num_readers].need_mb = &need_mb;
+	registry[num_readers].rcu_reader_qs_gp = &rcu_reader_qs_gp;
 	num_readers++;
 }
 
@@ -238,7 +262,7 @@ static void rcu_remove_reader(pthread_t id)
 			memcpy(index, &registry[num_readers - 1],
 				sizeof(struct reader_registry));
 			registry[num_readers - 1].tid = 0;
-			registry[num_readers - 1].urcu_active_readers = NULL;
+			registry[num_readers - 1].rcu_reader_qs_gp = NULL;
 			num_readers--;
 			return;
 		}
@@ -252,10 +276,16 @@ void rcu_register_thread(void)
 	internal_urcu_lock();
 	rcu_add_reader(pthread_self());
 	internal_urcu_unlock();
+	_rcu_thread_online();
 }
 
 void rcu_unregister_thread(void)
 {
+	/*
+	 * We have to make the thread offline otherwise we end up dealocking
+	 * with a waiting writer.
+	 */
+	_rcu_thread_offline();
 	internal_urcu_lock();
 	rcu_remove_reader(pthread_self());
 	internal_urcu_unlock();