X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=2d5c510aa6744418c5557d642b451e0afae415cd;hp=42a5829fb894f513db3cae9f59f832e24ae0ca26;hb=708d89f0b396d20522fe87cc80d91072bb9fcb02;hpb=bab44e28a30b837d72cb3b0cd64fe86f93e9ff61

diff --git a/urcu.c b/urcu.c
index 42a5829..2d5c510 100644
--- a/urcu.c
+++ b/urcu.c
@@ -63,7 +63,7 @@
 
 #ifdef RCU_MEMBARRIER
 static int init_done;
-int has_sys_membarrier;
+int rcu_has_sys_membarrier;
 
 void __attribute__((constructor)) rcu_init(void);
 #endif
@@ -83,7 +83,7 @@ void __attribute__((destructor)) rcu_exit(void);
 
 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
 
-int32_t gp_futex;
+int32_t rcu_gp_futex;
 
 /*
  * Global grace period counter.
@@ -100,8 +100,8 @@ unsigned long rcu_gp_ctr = RCU_GP_COUNT;
 DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
 
 #ifdef DEBUG_YIELD
-unsigned int yield_active;
-DEFINE_URCU_TLS(unsigned int, rand_yield);
+unsigned int rcu_yield_active;
+DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
 #endif
 
 static CDS_LIST_HEAD(registry);
@@ -140,7 +140,7 @@ static void mutex_unlock(pthread_mutex_t *mutex)
 #ifdef RCU_MEMBARRIER
 static void smp_mb_master(int group)
 {
-	if (caa_likely(has_sys_membarrier))
+	if (caa_likely(rcu_has_sys_membarrier))
 		membarrier(MEMBARRIER_EXPEDITED);
 	else
 		cmm_smp_mb();
@@ -210,43 +210,26 @@ static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
 	smp_mb_master(RCU_MB_GROUP);
-	if (uatomic_read(&gp_futex) == -1)
-		futex_async(&gp_futex, FUTEX_WAIT, -1,
+	if (uatomic_read(&rcu_gp_futex) == -1)
+		futex_async(&rcu_gp_futex, FUTEX_WAIT, -1,
 		      NULL, NULL, 0);
 }
 
-static void update_counter_and_wait(void)
+static void wait_for_readers(void)
 {
 	CDS_LIST_HEAD(qsreaders);
 	int wait_loops = 0;
 	struct rcu_reader *index, *tmp;
 
-	/* Switch parity: 0 -> 1, 1 -> 0 */
-	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
-
-	/*
-	 * Must commit rcu_gp_ctr update to memory before waiting for 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.
-	 */
-	cmm_barrier();
-
-	/*
-	 *
-	 * Adding a cmm_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.
-	 */
-	cmm_smp_mb();
-
 	/*
-	 * Wait for each thread URCU_TLS(rcu_reader).ctr count to become 0.
+	 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
+	 * indicate quiescence (not nested), or observe the current
+	 * rcu_gp_ctr value.
 	 */
 	for (;;) {
 		wait_loops++;
 		if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
-			uatomic_dec(&gp_futex);
+			uatomic_dec(&rcu_gp_futex);
 			/* Write futex before read reader_gp */
 			smp_mb_master(RCU_MB_GROUP);
 		}
@@ -261,7 +244,7 @@ static void update_counter_and_wait(void)
 			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
 				smp_mb_master(RCU_MB_GROUP);
-				uatomic_set(&gp_futex, 0);
+				uatomic_set(&rcu_gp_futex, 0);
 			}
 			break;
 		} else {
@@ -280,7 +263,7 @@ static void update_counter_and_wait(void)
 			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
 				smp_mb_master(RCU_MB_GROUP);
-				uatomic_set(&gp_futex, 0);
+				uatomic_set(&rcu_gp_futex, 0);
 			}
 			break;
 		} else {
@@ -316,12 +299,12 @@ void synchronize_rcu(void)
 	smp_mb_master(RCU_MB_GROUP);
 
 	/*
-	 * Wait for previous parity to be empty of readers.
+	 * Wait for readers to observe original parity or be quiescent.
 	 */
-	update_counter_and_wait();	/* 0 -> 1, wait readers in parity 0 */
+	wait_for_readers();
 
 	/*
-	 * Must finish waiting for quiescent state for parity 0 before
+	 * Must finish waiting for quiescent state for original parity before
 	 * 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
@@ -336,10 +319,29 @@ void synchronize_rcu(void)
 	 */
 	cmm_smp_mb();
 
+	/* Switch parity: 0 -> 1, 1 -> 0 */
+	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+
+	/*
+	 * Must commit rcu_gp_ctr update to memory before waiting for 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.
+	 */
+	cmm_barrier();
+
+	/*
+	 *
+	 * Adding a cmm_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.
+	 */
+	cmm_smp_mb();
+
 	/*
-	 * Wait for previous parity to be empty of readers.
+	 * Wait for readers to observe new parity or be quiescent.
 	 */
-	update_counter_and_wait();	/* 1 -> 0, wait readers in parity 1 */
+	wait_for_readers();
 
 	/* Finish waiting for reader threads before letting the old ptr being
 	 * freed. Must be done within rcu_gp_lock because it iterates on reader
@@ -389,7 +391,7 @@ void rcu_init(void)
 		return;
 	init_done = 1;
 	if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
-		has_sys_membarrier = 1;
+		rcu_has_sys_membarrier = 1;
 }
 #endif