X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=07661a3cb448b34505f24a8552a421741bb282bd;hp=c210a1341ade8a189752417249bb47bca73a03aa;hb=1e52eccf3cb657dccb197132f7cb47b683902538;hpb=538d7df5086144837beb7a9c1e2a94eb637b9904

diff --git a/urcu.c b/urcu.c
index c210a13..07661a3 100644
--- a/urcu.c
+++ b/urcu.c
@@ -36,7 +36,9 @@
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #include "urcu.h"
 
-#ifndef CONFIG_URCU_AVOID_SIGNALS
+#ifndef URCU_MB
+static int init_done;
+
 void __attribute__((constructor)) urcu_init(void);
 void __attribute__((destructor)) urcu_exit(void);
 #else
@@ -45,14 +47,14 @@ void urcu_init(void)
 }
 #endif
 
-int init_done;
+static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+int gp_futex;
 
 /*
  * Global grace period counter.
  * Contains the current RCU_GP_CTR_BIT.
- * Also has a RCU_GP_CTR_BIT of 1, to accelerate the reader fast path.
+ * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
  * Written to only by writer with mutex taken. Read by both writer and readers.
  */
 long urcu_gp_ctr = RCU_GP_COUNT;
@@ -81,7 +83,7 @@ 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;
 
@@ -108,7 +110,7 @@ void internal_urcu_lock(void)
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
 }
 
-void internal_urcu_unlock(void)
+static void internal_urcu_unlock(void)
 {
 	int ret;
 
@@ -127,20 +129,17 @@ static void switch_next_urcu_qparity(void)
 	STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
 }
 
-#ifdef CONFIG_URCU_AVOID_SIGNALS
-#ifdef HAS_INCOHERENT_CACHES
+#ifdef URCU_MB
 static void force_mb_single_thread(struct reader_registry *index)
 {
 	smp_mb();
 }
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
 
 static void force_mb_all_threads(void)
 {
 	smp_mb();
 }
-#else /* #ifdef CONFIG_URCU_AVOID_SIGNALS */
-#ifdef HAS_INCOHERENT_CACHES
+#else /* #ifdef URCU_MB */
 static void force_mb_single_thread(struct reader_registry *index)
 {
 	assert(registry);
@@ -163,7 +162,6 @@ static void force_mb_single_thread(struct reader_registry *index)
 	}
 	smp_mb();	/* read ->need_mb before ending the barrier */
 }
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
 
 static void force_mb_all_threads(void)
 {
@@ -206,7 +204,28 @@ static void force_mb_all_threads(void)
 	}
 	smp_mb();	/* read ->need_mb before ending the barrier */
 }
-#endif /* #else #ifdef CONFIG_URCU_AVOID_SIGNALS */
+#endif /* #else #ifdef URCU_MB */
+
+/*
+ * synchronize_rcu() waiting. Single thread.
+ */
+static void wait_gp(struct reader_registry *index)
+{
+	atomic_dec(&gp_futex);
+	force_mb_single_thread(index); /* Write futex before read reader_gp */
+	if (!rcu_old_gp_ongoing(index->urcu_active_readers)) {
+		/* Read reader_gp before write futex */
+		force_mb_single_thread(index);
+		/* Callbacks are queued, don't wait. */
+		atomic_set(&gp_futex, 0);
+	} else {
+		/* Read reader_gp before read futex */
+		force_mb_single_thread(index);
+		if (atomic_read(&gp_futex) == -1)
+			futex(&gp_futex, FUTEX_WAIT, -1,
+			      NULL, NULL, 0);
+	}
+}
 
 void wait_for_quiescent_state(void)
 {
@@ -218,20 +237,30 @@ void wait_for_quiescent_state(void)
 	 * Wait for each thread urcu_active_readers count to become 0.
 	 */
 	for (index = registry; index < registry + num_readers; index++) {
+		int wait_loops = 0;
 #ifndef HAS_INCOHERENT_CACHES
-		while (rcu_old_gp_ongoing(index->urcu_active_readers))
-			cpu_relax();
+		while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
+			if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
+				wait_gp(index);
+			} else {
+				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.
 		 */
 		while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
-			if (wait_loops++ == KICK_READER_LOOPS) {
+			switch (wait_loops++) {
+			case RCU_QS_ACTIVE_ATTEMPTS:
+				wait_gp(index);
+				break;
+			case KICK_READER_LOOPS:
 				force_mb_single_thread(index);
 				wait_loops = 0;
-			} else {
+				break;
+			default:
 				cpu_relax();
 			}
 		}
@@ -347,6 +376,12 @@ void *rcu_xchg_pointer_sym(void **p, void *v)
 	return xchg(p, v);
 }
 
+void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new)
+{
+	wmb();
+	return cmpxchg(p, old, _new);
+}
+
 void *rcu_publish_content_sym(void **p, void *v)
 {
 	void *oldptr;
@@ -420,7 +455,7 @@ void rcu_unregister_thread(void)
 	internal_urcu_unlock();
 }
 
-#ifndef CONFIG_URCU_AVOID_SIGNALS
+#ifndef URCU_MB
 static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
 {
 	/*
@@ -473,4 +508,4 @@ void urcu_exit(void)
 	assert(act.sa_sigaction == sigurcu_handler);
 	free(registry);
 }
-#endif /* #ifndef CONFIG_URCU_AVOID_SIGNALS */
+#endif /* #ifndef URCU_MB */