Implement sched_yield UP support

[userspace-rcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index 07661a3cb448b34505f24a8552a421741bb282bd..d9604973e37f850a1036599dd0763519b42ed6b5 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -49,8 +49,6 @@ void urcu_init(void)
 
 static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-int gp_futex;
-
 /*
  * Global grace period counter.
  * Contains the current RCU_GP_CTR_BIT.
@@ -130,16 +128,19 @@ static void switch_next_urcu_qparity(void)
 }
 
 #ifdef URCU_MB
+#ifdef HAS_INCOHERENT_CACHES
 static void force_mb_single_thread(struct reader_registry *index)
 {
        smp_mb();
 }
+#endif /* #ifdef HAS_INCOHERENT_CACHES */
 
 static void force_mb_all_threads(void)
 {
        smp_mb();
 }
 #else /* #ifdef URCU_MB */
+#ifdef HAS_INCOHERENT_CACHES
 static void force_mb_single_thread(struct reader_registry *index)
 {
        assert(registry);
@@ -162,6 +163,7 @@ static void force_mb_single_thread(struct reader_registry *index)
        }
        smp_mb();       /* read ->need_mb before ending the barrier */
 }
+#endif /* #ifdef HAS_INCOHERENT_CACHES */
 
 static void force_mb_all_threads(void)
 {
@@ -206,27 +208,6 @@ static void force_mb_all_threads(void)
 }
 #endif /* #else #ifdef URCU_MB */
 
-/*
- * synchronize_rcu() waiting. Single thread.
- */
-static void wait_gp(struct reader_registry *index)
-{
-       atomic_dec(&gp_futex);
-       force_mb_single_thread(index); /* Write futex before read reader_gp */
-       if (!rcu_old_gp_ongoing(index->urcu_active_readers)) {
-               /* Read reader_gp before write futex */
-               force_mb_single_thread(index);
-               /* Callbacks are queued, don't wait. */
-               atomic_set(&gp_futex, 0);
-       } else {
-               /* Read reader_gp before read futex */
-               force_mb_single_thread(index);
-               if (atomic_read(&gp_futex) == -1)
-                       futex(&gp_futex, FUTEX_WAIT, -1,
-                             NULL, NULL, 0);
-       }
-}
-
 void wait_for_quiescent_state(void)
 {
        struct reader_registry *index;
@@ -241,7 +222,7 @@ void wait_for_quiescent_state(void)
 #ifndef HAS_INCOHERENT_CACHES
                while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
                        if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
-                               wait_gp(index);
+                               sched_yield();  /* ideally sched_yield_to() */
                        } else {
                                cpu_relax();
                        }
@@ -254,7 +235,7 @@ void wait_for_quiescent_state(void)
                while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
                        switch (wait_loops++) {
                        case RCU_QS_ACTIVE_ATTEMPTS:
-                               wait_gp(index);
+                               sched_yield();  /* ideally sched_yield_to() */
                                break;
                        case KICK_READER_LOOPS:
                                force_mb_single_thread(index);
@@ -278,6 +259,8 @@ void synchronize_rcu(void)
        /* Write new ptr before changing the qparity */
        force_mb_all_threads();
 
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
+
        switch_next_urcu_qparity();     /* 0 -> 1 */
 
        /*
@@ -337,6 +320,8 @@ void synchronize_rcu(void)
         */
        wait_for_quiescent_state();     /* Wait readers in parity 1 */
 
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
+
        /* Finish waiting for reader threads before letting the old ptr being
         * freed. Must be done within internal_urcu_lock because it iterates on
         * reader threads. */