X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=52cb04aee9ff1b1b5a7b2caef45d6d5b5317ba77;hp=6b6d3af6711ce44647ebd04dfc796c0495c988b7;hb=2819ef641bb6e2f7aa60c28f3a8f5ad252aa7d00;hpb=a4ce4f122a4e615b6426fa876df38f5c3ea5fb8a

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 6b6d3af..52cb04a 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -39,6 +39,10 @@
 #include "urcu/map/urcu-qsbr.h"
 #define BUILD_QSBR_LIB
 #include "urcu/static/urcu-qsbr.h"
+#include "urcu-pointer.h"
+#include "urcu/tls-compat.h"
+
+#include "urcu-die.h"
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #undef _LGPL_SOURCE
@@ -47,7 +51,21 @@
 
 void __attribute__((destructor)) rcu_exit(void);
 
+/*
+ * rcu_gp_lock ensures mutual exclusion between threads calling
+ * synchronize_rcu().
+ */
 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * rcu_registry_lock ensures mutual exclusion between threads
+ * registering and unregistering themselves to/from the registry, and
+ * with threads reading that registry from synchronize_rcu(). However,
+ * this lock is not held all the way through the completion of awaiting
+ * for the grace period. It is sporadically released between iterations
+ * on the registry.
+ * rcu_registry_lock may nest inside rcu_gp_lock.
+ */
+static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
 
 int32_t gp_futex;
 
@@ -65,11 +83,11 @@ unsigned long rcu_gp_ctr = RCU_GP_ONLINE;
  * Written to only by each individual reader. Read by both the reader and the
  * writers.
  */
-struct rcu_reader __thread rcu_reader;
+__DEFINE_URCU_TLS_GLOBAL(struct rcu_reader, rcu_reader);
 
 #ifdef DEBUG_YIELD
 unsigned int yield_active;
-unsigned int __thread rand_yield;
+__DEFINE_URCU_TLS_GLOBAL(unsigned int, rand_yield);
 #endif
 
 static CDS_LIST_HEAD(registry);
@@ -80,17 +98,12 @@ static void mutex_lock(pthread_mutex_t *mutex)
 
 #ifndef DISTRUST_SIGNALS_EXTREME
 	ret = pthread_mutex_lock(mutex);
-	if (ret) {
-		perror("Error in pthread mutex lock");
-		exit(-1);
-	}
+	if (ret)
+		urcu_die(ret);
 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
 	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");
-			exit(-1);
-		}
+		if (ret != EBUSY && ret != EINTR)
+			urcu_die(ret);
 		poll(NULL,0,10);
 	}
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
@@ -101,10 +114,8 @@ static void mutex_unlock(pthread_mutex_t *mutex)
 	int ret;
 
 	ret = pthread_mutex_unlock(mutex);
-	if (ret) {
-		perror("Error in pthread mutex unlock");
-		exit(-1);
-	}
+	if (ret)
+		urcu_die(ret);
 }
 
 /*
@@ -114,15 +125,32 @@ static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
 	cmm_smp_rmb();
-	if (uatomic_read(&gp_futex) == -1)
-		futex_noasync(&gp_futex, FUTEX_WAIT, -1,
-		      NULL, NULL, 0);
+	if (uatomic_read(&gp_futex) != -1)
+		return;
+	while (futex_noasync(&gp_futex, FUTEX_WAIT, -1,
+			NULL, NULL, 0)) {
+		switch (errno) {
+		case EWOULDBLOCK:
+			/* Value already changed. */
+			return;
+		case EINTR:
+			/* Retry if interrupted by signal. */
+			break;	/* Get out of switch. */
+		default:
+			/* Unexpected error. */
+			urcu_die(errno);
+		}
+	}
 }
 
+/*
+ * Always called with rcu_registry lock held. Releases this lock between
+ * iterations and grabs it again. Holds the lock when it returns.
+ */
 static void update_counter_and_wait(void)
 {
 	CDS_LIST_HEAD(qsreaders);
-	int wait_loops = 0;
+	unsigned int wait_loops = 0;
 	struct rcu_reader *index, *tmp;
 
 #if (CAA_BITS_PER_LONG < 64)
@@ -138,7 +166,7 @@ static void update_counter_and_wait(void)
 	 * quiescent state. Failure to do so could result in the writer
 	 * waiting forever while new readers are always accessing data
 	 * (no progress). Enforce compiler-order of store to rcu_gp_ctr
-	 * before load rcu_reader ctr.
+	 * before load URCU_TLS(rcu_reader).ctr.
 	 */
 	cmm_barrier();
 
@@ -153,7 +181,8 @@ static void update_counter_and_wait(void)
 	 * Wait for each thread rcu_reader_qs_gp count to become 0.
 	 */
 	for (;;) {
-		wait_loops++;
+		if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
+			wait_loops++;
 		if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
 			uatomic_set(&gp_futex, -1);
 			/*
@@ -180,6 +209,8 @@ static void update_counter_and_wait(void)
 			}
 			break;
 		} else {
+			/* Temporarily unlock the registry lock. */
+			mutex_unlock(&rcu_registry_lock);
 			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
 				wait_gp();
 			} else {
@@ -189,6 +220,8 @@ static void update_counter_and_wait(void)
 				cmm_smp_mb();
 #endif /* #else #ifndef HAS_INCOHERENT_CACHES */
 			}
+			/* Re-lock the registry lock before the next loop. */
+			mutex_lock(&rcu_registry_lock);
 		}
 	}
 	/* put back the reader list in the registry */
@@ -205,7 +238,7 @@ void synchronize_rcu(void)
 {
 	unsigned long was_online;
 
-	was_online = rcu_reader.ctr;
+	was_online = URCU_TLS(rcu_reader).ctr;
 
 	/* All threads should read qparity before accessing data structure
 	 * where new ptr points to.  In the "then" case, rcu_thread_offline
@@ -221,12 +254,15 @@ void synchronize_rcu(void)
 		cmm_smp_mb();
 
 	mutex_lock(&rcu_gp_lock);
+	mutex_lock(&rcu_registry_lock);
 
 	if (cds_list_empty(&registry))
 		goto out;
 
 	/*
 	 * Wait for previous parity to be empty of readers.
+	 * update_counter_and_wait() can release and grab again
+	 * rcu_registry_lock interally.
 	 */
 	update_counter_and_wait();	/* 0 -> 1, wait readers in parity 0 */
 
@@ -235,7 +271,7 @@ void synchronize_rcu(void)
 	 * committing next rcu_gp_ctr update to memory. Failure to
 	 * do so could result in the writer waiting forever while new
 	 * readers are always accessing data (no progress).  Enforce
-	 * compiler-order of load rcu_reader ctr before store to
+	 * compiler-order of load URCU_TLS(rcu_reader).ctr before store to
 	 * rcu_gp_ctr.
 	 */
 	cmm_barrier();
@@ -249,9 +285,12 @@ void synchronize_rcu(void)
 
 	/*
 	 * Wait for previous parity to be empty of readers.
+	 * update_counter_and_wait() can release and grab again
+	 * rcu_registry_lock interally.
 	 */
 	update_counter_and_wait();	/* 1 -> 0, wait readers in parity 1 */
 out:
+	mutex_unlock(&rcu_registry_lock);
 	mutex_unlock(&rcu_gp_lock);
 
 	/*
@@ -268,7 +307,7 @@ void synchronize_rcu(void)
 {
 	unsigned long was_online;
 
-	was_online = rcu_reader.ctr;
+	was_online = URCU_TLS(rcu_reader).ctr;
 
 	/*
 	 * Mark the writer thread offline to make sure we don't wait for
@@ -281,10 +320,16 @@ void synchronize_rcu(void)
 		cmm_smp_mb();
 
 	mutex_lock(&rcu_gp_lock);
+	mutex_lock(&rcu_registry_lock);
 	if (cds_list_empty(&registry))
 		goto out;
+	/*
+	 * update_counter_and_wait() can release and grab again
+	 * rcu_registry_lock interally.
+	 */
 	update_counter_and_wait();
 out:
+	mutex_unlock(&rcu_registry_lock);
 	mutex_unlock(&rcu_gp_lock);
 
 	if (was_online)
@@ -325,12 +370,12 @@ void rcu_thread_online(void)
 
 void rcu_register_thread(void)
 {
-	rcu_reader.tid = pthread_self();
-	assert(rcu_reader.ctr == 0);
+	URCU_TLS(rcu_reader).tid = pthread_self();
+	assert(URCU_TLS(rcu_reader).ctr == 0);
 
-	mutex_lock(&rcu_gp_lock);
-	cds_list_add(&rcu_reader.node, &registry);
-	mutex_unlock(&rcu_gp_lock);
+	mutex_lock(&rcu_registry_lock);
+	cds_list_add(&URCU_TLS(rcu_reader).node, &registry);
+	mutex_unlock(&rcu_registry_lock);
 	_rcu_thread_online();
 }
 
@@ -341,9 +386,9 @@ void rcu_unregister_thread(void)
 	 * with a waiting writer.
 	 */
 	_rcu_thread_offline();
-	mutex_lock(&rcu_gp_lock);
-	cds_list_del(&rcu_reader.node);
-	mutex_unlock(&rcu_gp_lock);
+	mutex_lock(&rcu_registry_lock);
+	cds_list_del(&URCU_TLS(rcu_reader).node);
+	mutex_unlock(&rcu_registry_lock);
 }
 
 void rcu_exit(void)
@@ -355,5 +400,7 @@ void rcu_exit(void)
 	 */
 }
 
+DEFINE_RCU_FLAVOR(rcu_flavor);
+
 #include "urcu-call-rcu-impl.h"
 #include "urcu-defer-impl.h"