X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu.c;h=e9df01bc7b56cdb25b6e225e6ba46d2182ab28be;hb=2819ef641bb6e2f7aa60c28f3a8f5ad252aa7d00;hp=1d4bf7afb04030155f7cb88d4dcb2cf8e2518a66;hpb=ed42f6768d2116c47ca9ef2c17927a45f6b98f04;p=userspace-rcu.git

diff --git a/urcu.c b/urcu.c
index 1d4bf7a..e9df01b 100644
--- a/urcu.c
+++ b/urcu.c
@@ -219,14 +219,40 @@ static void smp_mb_master(int group)
 
 /*
  * synchronize_rcu() waiting. Single thread.
+ * Always called with rcu_registry lock held. Releases this lock and
+ * grabs it again. Holds the lock when it returns.
  */
 static void wait_gp(void)
 {
-	/* Read reader_gp before read futex */
+	/*
+	 * Read reader_gp before read futex. smp_mb_master() needs to
+	 * be called with the rcu registry lock held in RCU_SIGNAL
+	 * flavor.
+	 */
 	smp_mb_master(RCU_MB_GROUP);
-	if (uatomic_read(&gp_futex) == -1)
-		futex_async(&gp_futex, FUTEX_WAIT, -1,
-		      NULL, NULL, 0);
+	/* Temporarily unlock the registry lock. */
+	mutex_unlock(&rcu_registry_lock);
+	if (uatomic_read(&gp_futex) != -1)
+		goto end;
+	while (futex_async(&gp_futex, FUTEX_WAIT, -1,
+			NULL, NULL, 0)) {
+		switch (errno) {
+		case EWOULDBLOCK:
+			/* Value already changed. */
+			goto end;
+		case EINTR:
+			/* Retry if interrupted by signal. */
+			break;	/* Get out of switch. */
+		default:
+			/* Unexpected error. */
+			urcu_die(errno);
+		}
+	}
+end:
+	/*
+	 * Re-lock the registry lock before the next loop.
+	 */
+	mutex_lock(&rcu_registry_lock);
 }
 
 /*
@@ -287,14 +313,19 @@ 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)
+			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+				/* wait_gp unlocks/locks registry lock. */
 				wait_gp();
-			else
+			} else {
+				/* Temporarily unlock the registry lock. */
+				mutex_unlock(&rcu_registry_lock);
 				caa_cpu_relax();
-			/* Re-lock the registry lock before the next loop. */
-			mutex_lock(&rcu_registry_lock);
+				/*
+				 * Re-lock the registry lock before the
+				 * next loop.
+				 */
+				mutex_lock(&rcu_registry_lock);
+			}
 		}
 #else /* #ifndef HAS_INCOHERENT_CACHES */
 		/*
@@ -314,16 +345,20 @@ void update_counter_and_wait(void)
 				smp_mb_master(RCU_MB_GROUP);
 				wait_gp_loops = 0;
 			}
-			/* Temporarily unlock the registry lock. */
-			mutex_unlock(&rcu_registry_lock);
 			if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+				/* wait_gp unlocks/locks registry lock. */
 				wait_gp();
 				wait_gp_loops++;
 			} else {
+				/* Temporarily unlock the registry lock. */
+				mutex_unlock(&rcu_registry_lock);
 				caa_cpu_relax();
+				/*
+				 * Re-lock the registry lock before the
+				 * next loop.
+				 */
+				mutex_lock(&rcu_registry_lock);
 			}
-			/* Re-lock the registry lock before the next loop. */
-			mutex_lock(&rcu_registry_lock);
 		}
 #endif /* #else #ifndef HAS_INCOHERENT_CACHES */
 	}