X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=ae3490f7cb2cdc1f7cdb1d26f77c0ee22620e9eb;hp=da6839f0c25b88b4262e9a615bd197220789c185;hb=5e81fed7cc48d0e14b7478ec1152c3ca2bd01f97;hpb=ed1b099ef8acd1396dbde7c7150d1a5eb16ce8a6

diff --git a/urcu.c b/urcu.c
index da6839f..ae3490f 100644
--- a/urcu.c
+++ b/urcu.c
@@ -53,15 +53,33 @@
 /*
  * If a reader is really non-cooperative and refuses to commit its
  * rcu_active_readers count to memory (there is no barrier in the reader
- * per-se), kick it after a few loops waiting for it.
+ * per-se), kick it after 10 loops waiting for it.
  */
-#define KICK_READER_LOOPS 10000
+#define KICK_READER_LOOPS 	10
 
 /*
  * Active attempts to check for reader Q.S. before calling futex().
  */
 #define RCU_QS_ACTIVE_ATTEMPTS 100
 
+/*
+ * RCU_MEMBARRIER is only possibly available on Linux.
+ */
+#if defined(RCU_MEMBARRIER) && defined(__linux__)
+#include <urcu/syscall-compat.h>
+#endif
+
+/* If the headers do not support SYS_membarrier, fall back on RCU_MB */
+#ifdef SYS_membarrier
+# define membarrier(...)		syscall(SYS_membarrier, __VA_ARGS__)
+#else
+# define membarrier(...)		-ENOSYS
+#endif
+
+#define MEMBARRIER_EXPEDITED		(1 << 0)
+#define MEMBARRIER_DELAYED		(1 << 1)
+#define MEMBARRIER_QUERY		(1 << 16)
+
 #ifdef RCU_MEMBARRIER
 static int init_done;
 int rcu_has_sys_membarrier;
@@ -83,7 +101,7 @@ void __attribute__((destructor)) rcu_exit(void);
 #endif
 
 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
-struct urcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
+struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
 
 /*
  * Written to only by each individual reader. Read by both the reader and the
@@ -91,11 +109,6 @@ struct urcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
  */
 DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
 
-#ifdef DEBUG_YIELD
-unsigned int rcu_yield_active;
-DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
-#endif
-
 static CDS_LIST_HEAD(registry);
 
 /*
@@ -139,7 +152,7 @@ static void mutex_unlock(pthread_mutex_t *mutex)
 static void smp_mb_master(int group)
 {
 	if (caa_likely(rcu_has_sys_membarrier))
-		membarrier(MEMBARRIER_EXPEDITED);
+		(void) membarrier(MEMBARRIER_EXPEDITED);
 	else
 		cmm_smp_mb();
 }
@@ -217,8 +230,11 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 			struct cds_list_head *cur_snap_readers,
 			struct cds_list_head *qsreaders)
 {
-	int wait_loops = 0;
+	unsigned int wait_loops = 0;
 	struct rcu_reader *index, *tmp;
+#ifdef HAS_INCOHERENT_CACHES
+	unsigned int wait_gp_loops = 0;
+#endif /* HAS_INCOHERENT_CACHES */
 
 	/*
 	 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
@@ -226,8 +242,9 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 	 * rcu_gp.ctr value.
 	 */
 	for (;;) {
-		wait_loops++;
-		if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+		if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
+			wait_loops++;
+		if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
 			uatomic_dec(&rcu_gp.futex);
 			/* Write futex before read reader_gp */
 			smp_mb_master(RCU_MB_GROUP);
@@ -258,14 +275,14 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 
 #ifndef HAS_INCOHERENT_CACHES
 		if (cds_list_empty(input_readers)) {
-			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
 				smp_mb_master(RCU_MB_GROUP);
 				uatomic_set(&rcu_gp.futex, 0);
 			}
 			break;
 		} else {
-			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
+			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
 				wait_gp();
 			else
 				caa_cpu_relax();
@@ -277,22 +294,21 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 		 * for too long.
 		 */
 		if (cds_list_empty(input_readers)) {
-			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
 				/* Read reader_gp before write futex */
 				smp_mb_master(RCU_MB_GROUP);
 				uatomic_set(&rcu_gp.futex, 0);
 			}
 			break;
 		} else {
-			switch (wait_loops) {
-			case RCU_QS_ACTIVE_ATTEMPTS:
-				wait_gp();
-				break; /* only escape switch */
-			case KICK_READER_LOOPS:
+			if (wait_gp_loops == KICK_READER_LOOPS) {
 				smp_mb_master(RCU_MB_GROUP);
-				wait_loops = 0;
-				break; /* only escape switch */
-			default:
+				wait_gp_loops = 0;
+			}
+			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+				wait_gp();
+				wait_gp_loops++;
+			} else {
 				caa_cpu_relax();
 			}
 		}
@@ -495,14 +511,14 @@ void rcu_init(void)
 
 void rcu_exit(void)
 {
-	struct sigaction act;
-	int ret;
-
-	ret = sigaction(SIGRCU, NULL, &act);
-	if (ret)
-		urcu_die(errno);
-	assert(act.sa_sigaction == sigrcu_handler);
-	assert(cds_list_empty(&registry));
+	/*
+	 * Don't unregister the SIGRCU signal handler anymore, because
+	 * call_rcu threads could still be using it shortly before the
+	 * application exits.
+	 * Assertion disabled because call_rcu threads are now rcu
+	 * readers, and left running at exit.
+	 * assert(cds_list_empty(&registry));
+	 */
 }
 
 #endif /* #ifdef RCU_SIGNAL */