Version 0.7.17

[userspace-rcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index 5cb470bcaea9e61b312a8e2d839c14ab88eacc80..e9df01bc7b56cdb25b6e225e6ba46d2182ab28be 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -26,6 +26,7 @@
 #define _BSD_SOURCE
 #define _GNU_SOURCE
 #define _LGPL_SOURCE
+#define _DEFAULT_SOURCE
 #include <stdio.h>
 #include <pthread.h>
 #include <signal.h>
@@ -218,14 +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);
 }
 
 /*
@@ -286,14 +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 */
                /*
@@ -313,16 +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 */
        }