X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-bp.c;h=1b0bd6950da04533c35bf00a5c131ac4da3e470b;hp=d841be6351bf8a30368bbe4a57e794f7dc6112af;hb=ee39cfb61d2a389db3342751762412f332a3e851;hpb=02be55611d3b1c7bf4fdfcb3a9c98f621882d417

diff --git a/urcu-bp.c b/urcu-bp.c
index d841be6..1b0bd69 100644
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -45,7 +45,7 @@
 
 void __attribute__((destructor)) rcu_bp_exit(void);
 
-static pthread_mutex_t rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
 
 #ifdef DEBUG_YIELD
 unsigned int yield_active;
@@ -78,18 +78,18 @@ static struct registry_arena registry_arena;
 
 static void rcu_gc_registry(void);
 
-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");
@@ -105,33 +105,40 @@ 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);
 	}
 }
 
-/*
- * called with rcu_mutex held.
- */
-static void switch_next_rcu_qparity(void)
-{
-	STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
-}
-
-void wait_for_quiescent_state(void)
+void update_counter_and_wait(void)
 {
 	LIST_HEAD(qsreaders);
 	int wait_loops = 0;
 	struct rcu_reader *index, *tmp;
 
-	if (list_empty(&registry))
-		return;
+	/* Switch parity: 0 -> 1, 1 -> 0 */
+	STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+
+	/*
+	 * Must commit qparity update to memory before waiting for other parity
+	 * quiescent state. Failure to do so could result in the writer waiting
+	 * forever while new readers are always accessing data (no progress).
+	 * Ensured by STORE_SHARED and LOAD_SHARED.
+	 */
+
+	/*
+	 * Adding a smp_mb() which is _not_ formally required, but makes the
+	 * model easier to understand. It does not have a big performance impact
+	 * anyway, given this is the write-side.
+	 */
+	smp_mb();
+
 	/*
 	 * Wait for each thread rcu_reader.ctr count to become 0.
 	 */
@@ -165,46 +172,23 @@ void synchronize_rcu(void)
 	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
 	assert(!ret);
 
-	internal_rcu_lock();
+	mutex_lock(&rcu_gp_lock);
 
-	/* Remove old registry elements */
-	rcu_gc_registry();
+	if (list_empty(&registry))
+		goto out;
 
 	/* 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. */
 	/* Write new ptr before changing the qparity */
 	smp_mb();
 
-	switch_next_rcu_qparity();	/* 0 -> 1 */
-
-	/*
-	 * Must commit qparity update to memory before waiting for parity
-	 * 0 quiescent state. Failure to do so could result in the writer
-	 * waiting forever while new readers are always accessing data (no
-	 * progress).
-	 * Ensured by STORE_SHARED and LOAD_SHARED.
-	 */
-
-	/*
-	 * Adding a smp_mb() which is _not_ formally required, but makes the
-	 * model easier to understand. It does not have a big performance impact
-	 * anyway, given this is the write-side.
-	 */
-	smp_mb();
+	/* Remove old registry elements */
+	rcu_gc_registry();
 
 	/*
 	 * Wait for previous parity to be empty of readers.
 	 */
-	wait_for_quiescent_state();	/* Wait readers in parity 0 */
-
-	/*
-	 * Must finish waiting for quiescent state for parity 0 before
-	 * committing qparity update to memory. Failure to do so could result in
-	 * the writer waiting forever while new readers are always accessing
-	 * data (no progress).
-	 * Ensured by STORE_SHARED and LOAD_SHARED.
-	 */
+	update_counter_and_wait();	/* 0 -> 1, wait readers in parity 0 */
 
 	/*
 	 * Adding a smp_mb() which is _not_ formally required, but makes the
@@ -213,34 +197,18 @@ void synchronize_rcu(void)
 	 */
 	smp_mb();
 
-	switch_next_rcu_qparity();	/* 1 -> 0 */
-
 	/*
-	 * Must commit qparity update to memory before waiting for parity
-	 * 1 quiescent state. Failure to do so could result in the writer
-	 * waiting forever while new readers are always accessing data (no
-	 * progress).
-	 * Ensured by STORE_SHARED and LOAD_SHARED.
-	 */
-
-	/*
-	 * Adding a smp_mb() which is _not_ formally required, but makes the
-	 * model easier to understand. It does not have a big performance impact
-	 * anyway, given this is the write-side.
+	 * Wait for previous parity to be empty of readers.
 	 */
-	smp_mb();
+	update_counter_and_wait();	/* 1 -> 0, wait readers in parity 1 */
 
 	/*
-	 * Wait for previous parity to be empty of readers.
+	 * Finish waiting for reader threads before letting the old ptr being
+	 * freed.
 	 */
-	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. */
 	smp_mb();
-
-	internal_rcu_unlock();
+out:
+	mutex_unlock(&rcu_gp_lock);
 	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 	assert(!ret);
 }
@@ -355,9 +323,9 @@ void rcu_bp_register(void)
 	if (rcu_reader)
 		goto end;
 
-	internal_rcu_lock();
+	mutex_lock(&rcu_gp_lock);
 	add_thread();
-	internal_rcu_unlock();
+	mutex_unlock(&rcu_gp_lock);
 end:
 	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 	assert(!ret);