X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu.c;h=7b75d4c545da73765d78fa168d628d3d4513e9f5;hb=cf5271eed768bea133b1916eca1d1917920e3105;hp=3132e59277bf782f9e2e03cb3b0f862981b80a2a;hpb=78ff941908d1c336106c06649c0892015cc98e18;p=userspace-rcu.git

diff --git a/urcu.c b/urcu.c
index 3132e59..7b75d4c 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>
@@ -36,17 +37,26 @@
 /* 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
 
+#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_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 int gp_futex;
@@ -118,44 +128,24 @@ 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_readers(void)
+#ifdef RCU_MB
+static void smp_mb_heavy(void)
 {
 	smp_mb();
 }
-#else /* #ifdef RCU_MB */
-#if 0 /* unused */
-static void force_mb_single_thread(struct rcu_reader *index)
-{
-	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
 
+#ifdef RCU_SIGNAL
 static void force_mb_all_readers(void)
 {
 	struct rcu_reader *index;
@@ -198,7 +188,12 @@ static void force_mb_all_readers(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_readers(void)
 static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
-	force_mb_all_readers();
+	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_readers();
+			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_readers();
+				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_readers();
+				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_readers();
+				smp_mb_heavy();
 				wait_loops = 0;
 				break; /* only escape switch */
 			default:
@@ -289,7 +284,7 @@ void synchronize_rcu(void)
 	 * where new ptr points to. Must be done within internal_rcu_lock
 	 * because it iterates on reader threads.*/
 	/* Write new ptr before changing the qparity */
-	force_mb_all_readers();
+	smp_mb_heavy();
 
 	switch_next_rcu_qparity();	/* 0 -> 1 */
 
@@ -353,7 +348,7 @@ void synchronize_rcu(void)
 	/* 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_readers();
+	smp_mb_heavy();
 
 	internal_rcu_unlock();
 }
@@ -391,7 +386,18 @@ void rcu_unregister_thread(void)
 	internal_rcu_unlock();
 }
 
-#ifndef RCU_MB
+#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
+
+#ifdef RCU_SIGNAL
 static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
 {
 	/*
@@ -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 */