X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;ds=sidebyside;f=urcu.c;h=6e9589145cf789a06c00aa988cb01d8c3dcb27fa;hb=6abb4bd53503c325dc94b0c0f60b44b9550b462f;hp=c4b2b428787fbc519031f2c696773cd3300767bb;hpb=02be55611d3b1c7bf4fdfcb3a9c98f621882d417;p=userspace-rcu.git

diff --git a/urcu.c b/urcu.c
index c4b2b42..6e95891 100644
--- a/urcu.c
+++ b/urcu.c
@@ -23,6 +23,7 @@
  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  */
 
+#define _BSD_SOURCE
 #include <stdio.h>
 #include <pthread.h>
 #include <signal.h>
@@ -36,18 +37,27 @@
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #include "urcu.h"
 
-#ifndef RCU_MB
+#ifdef RCU_MEMBARRIER
 static int init_done;
+int has_sys_membarrier;
 
 void __attribute__((constructor)) rcu_init(void);
-void __attribute__((destructor)) rcu_exit(void);
-#else
+#endif
+
+#ifdef RCU_MB
 void rcu_init(void)
 {
 }
 #endif
 
-static pthread_mutex_t rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+#ifdef RCU_SIGNAL
+static int init_done;
+
+void __attribute__((constructor)) rcu_init(void);
+void __attribute__((destructor)) rcu_exit(void);
+#endif
+
+static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
 
 int gp_futex;
 
@@ -72,18 +82,18 @@ unsigned int __thread rand_yield;
 
 static LIST_HEAD(registry);
 
-static void internal_rcu_lock(void)
+static void mutex_lock(pthread_mutex_t *mutex)
 {
 	int ret;
 
 #ifndef DISTRUST_SIGNALS_EXTREME
-	ret = pthread_mutex_lock(&rcu_mutex);
+	ret = pthread_mutex_lock(mutex);
 	if (ret) {
 		perror("Error in pthread mutex lock");
 		exit(-1);
 	}
 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
-	while ((ret = pthread_mutex_trylock(&rcu_mutex)) != 0) {
+	while ((ret = pthread_mutex_trylock(mutex)) != 0) {
 		if (ret != EBUSY && ret != EINTR) {
 			printf("ret = %d, errno = %d\n", ret, errno);
 			perror("Error in pthread mutex lock");
@@ -99,11 +109,11 @@ static void internal_rcu_lock(void)
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
 }
 
-static void internal_rcu_unlock(void)
+static void mutex_unlock(pthread_mutex_t *mutex)
 {
 	int ret;
 
-	ret = pthread_mutex_unlock(&rcu_mutex);
+	ret = pthread_mutex_unlock(mutex);
 	if (ret) {
 		perror("Error in pthread mutex unlock");
 		exit(-1);
@@ -111,52 +121,32 @@ static void internal_rcu_unlock(void)
 }
 
 /*
- * called with rcu_mutex held.
+ * called with rcu_gp_lock held.
  */
 static void switch_next_rcu_qparity(void)
 {
 	STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
 }
 
-#ifdef RCU_MB
-#if 0 /* unused */
-static void force_mb_single_thread(struct rcu_reader *index)
+#ifdef RCU_MEMBARRIER
+static void smp_mb_heavy(void)
 {
-	smp_mb();
+	if (likely(has_sys_membarrier))
+		membarrier(MEMBARRIER_EXPEDITED);
+	else
+		smp_mb();
 }
-#endif //0
+#endif
 
-static void force_mb_all_threads(void)
-{
-	smp_mb();
-}
-#else /* #ifdef RCU_MB */
-#if 0 /* unused */
-static void force_mb_single_thread(struct rcu_reader *index)
+#ifdef RCU_MB
+static void smp_mb_heavy(void)
 {
-	assert(!list_empty(&registry));
-	/*
-	 * pthread_kill has a smp_mb(). But beware, we assume it performs
-	 * a cache flush on architectures with non-coherent cache. Let's play
-	 * safe and don't assume anything : we use smp_mc() to make sure the
-	 * cache flush is enforced.
-	 */
-	index->need_mb = 1;
-	smp_mc();	/* write ->need_mb before sending the signals */
-	pthread_kill(index->tid, SIGRCU);
 	smp_mb();
-	/*
-	 * Wait for sighandler (and thus mb()) to execute on every thread.
-	 * BUSY-LOOP.
-	 */
-	while (index->need_mb) {
-		poll(NULL, 0, 1);
-	}
-	smp_mb();	/* read ->need_mb before ending the barrier */
 }
-#endif //0
+#endif
 
-static void force_mb_all_threads(void)
+#ifdef RCU_SIGNAL
+static void force_mb_all_readers(void)
 {
 	struct rcu_reader *index;
 
@@ -198,7 +188,12 @@ static void force_mb_all_threads(void)
 	}
 	smp_mb();	/* read ->need_mb before ending the barrier */
 }
-#endif /* #else #ifdef RCU_MB */
+
+static void smp_mb_heavy(void)
+{
+	force_mb_all_readers();
+}
+#endif /* #ifdef RCU_SIGNAL */
 
 /*
  * synchronize_rcu() waiting. Single thread.
@@ -206,7 +201,7 @@ static void force_mb_all_threads(void)
 static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
-	force_mb_all_threads();
+	smp_mb_heavy();
 	if (uatomic_read(&gp_futex) == -1)
 		futex_async(&gp_futex, FUTEX_WAIT, -1,
 		      NULL, NULL, 0);
@@ -228,7 +223,7 @@ void wait_for_quiescent_state(void)
 		if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
 			uatomic_dec(&gp_futex);
 			/* Write futex before read reader_gp */
-			force_mb_all_threads();
+			smp_mb_heavy();
 		}
 
 		list_for_each_entry_safe(index, tmp, &registry, head) {
@@ -240,7 +235,7 @@ void wait_for_quiescent_state(void)
 		if (list_empty(&registry)) {
 			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
-				force_mb_all_threads();
+				smp_mb_heavy();
 				uatomic_set(&gp_futex, 0);
 			}
 			break;
@@ -258,7 +253,7 @@ void wait_for_quiescent_state(void)
 		if (list_empty(&registry)) {
 			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
-				force_mb_all_threads();
+				smp_mb_heavy();
 				uatomic_set(&gp_futex, 0);
 			}
 			break;
@@ -268,7 +263,7 @@ void wait_for_quiescent_state(void)
 				wait_gp();
 				break; /* only escape switch */
 			case KICK_READER_LOOPS:
-				force_mb_all_threads();
+				smp_mb_heavy();
 				wait_loops = 0;
 				break; /* only escape switch */
 			default:
@@ -283,13 +278,13 @@ void wait_for_quiescent_state(void)
 
 void synchronize_rcu(void)
 {
-	internal_rcu_lock();
+	mutex_lock(&rcu_gp_lock);
 
 	/* All threads should read qparity before accessing data structure
-	 * where new ptr points to. Must be done within internal_rcu_lock
-	 * because it iterates on reader threads.*/
+	 * where new ptr points to. Must be done within rcu_gp_lock because it
+	 * iterates on reader threads.*/
 	/* Write new ptr before changing the qparity */
-	force_mb_all_threads();
+	smp_mb_heavy();
 
 	switch_next_rcu_qparity();	/* 0 -> 1 */
 
@@ -351,11 +346,11 @@ void synchronize_rcu(void)
 	wait_for_quiescent_state();	/* Wait readers in parity 1 */
 
 	/* Finish waiting for reader threads before letting the old ptr being
-	 * freed. Must be done within internal_rcu_lock because it iterates on
-	 * reader threads. */
-	force_mb_all_threads();
+	 * freed. Must be done within rcu_gp_lock because it iterates on reader
+	 * threads. */
+	smp_mb_heavy();
 
-	internal_rcu_unlock();
+	mutex_unlock(&rcu_gp_lock);
 }
 
 /*
@@ -378,20 +373,31 @@ void rcu_register_thread(void)
 	assert(rcu_reader.need_mb == 0);
 	assert(rcu_reader.ctr == 0);
 
-	internal_rcu_lock();
+	mutex_lock(&rcu_gp_lock);
 	rcu_init();	/* In case gcc does not support constructor attribute */
 	list_add(&rcu_reader.head, &registry);
-	internal_rcu_unlock();
+	mutex_unlock(&rcu_gp_lock);
 }
 
 void rcu_unregister_thread(void)
 {
-	internal_rcu_lock();
+	mutex_lock(&rcu_gp_lock);
 	list_del(&rcu_reader.head);
-	internal_rcu_unlock();
+	mutex_unlock(&rcu_gp_lock);
+}
+
+#ifdef RCU_MEMBARRIER
+void rcu_init(void)
+{
+	if (init_done)
+		return;
+	init_done = 1;
+	if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
+		has_sys_membarrier = 1;
 }
+#endif
 
-#ifndef RCU_MB
+#ifdef RCU_SIGNAL
 static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
 {
 	/*
@@ -408,9 +414,9 @@ static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
  * rcu_init constructor. Called when the library is linked, but also when
  * reader threads are calling rcu_register_thread().
  * Should only be called by a single thread at a given time. This is ensured by
- * holing the internal_rcu_lock() from rcu_register_thread() or by running at
- * library load time, which should not be executed by multiple threads nor
- * concurrently with rcu_register_thread() anyway.
+ * holing the rcu_gp_lock from rcu_register_thread() or by running at library
+ * load time, which should not be executed by multiple threads nor concurrently
+ * with rcu_register_thread() anyway.
  */
 void rcu_init(void)
 {
@@ -444,4 +450,4 @@ void rcu_exit(void)
 	assert(act.sa_sigaction == sigrcu_handler);
 	assert(list_empty(&registry));
 }
-#endif /* #ifndef RCU_MB */
+#endif /* #ifdef RCU_SIGNAL */