Implement sched_yield UP support

[userspace-rcu.git] / urcu-qsbr.c

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index dac664935d7b898bd3dcce494845c7471c09749d..b42d7c4a42e3a4aa4e334ca457066327e969a85a 100644 (file)
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -39,8 +39,6 @@
 
 static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
-int gp_futex;
-
 /*
  * Global grace period counter.
  */
@@ -104,24 +102,6 @@ static void internal_urcu_unlock(void)
 /*
  * synchronize_rcu() waiting. Single thread.
  */
-static void wait_gp(struct reader_registry *index)
-{
-       atomic_dec(&gp_futex);
-       smp_mb(); /* Write futex before read reader_gp */
-       if (!rcu_gp_ongoing(index->rcu_reader_qs_gp)) {
-               /* Read reader_gp before write futex */
-               smp_mb();
-               /* Callbacks are queued, don't wait. */
-               atomic_set(&gp_futex, 0);
-       } else {
-               /* Read reader_gp before read futex */
-               smp_rmb();
-               if (atomic_read(&gp_futex) == -1)
-                       futex(&gp_futex, FUTEX_WAIT, -1,
-                             NULL, NULL, 0);
-       }
-}
-
 static void wait_for_quiescent_state(void)
 {
        struct reader_registry *index;
@@ -136,7 +116,7 @@ static void wait_for_quiescent_state(void)
 
                while (rcu_gp_ongoing(index->rcu_reader_qs_gp)) {
                        if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
-                               wait_gp(index);
+                               sched_yield();  /* ideally sched_yield_to() */
                        } else {
 #ifndef HAS_INCOHERENT_CACHES
                                cpu_relax();
@@ -184,6 +164,8 @@ void synchronize_rcu(void)
 
        internal_urcu_lock();
 
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
+
        switch_next_urcu_qparity();     /* 0 -> 1 */
 
        /*
@@ -222,6 +204,8 @@ void synchronize_rcu(void)
         */
        wait_for_quiescent_state();     /* Wait readers in parity 1 */
 
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
+
        internal_urcu_unlock();
 
        /*
@@ -249,8 +233,10 @@ void synchronize_rcu(void)
                STORE_SHARED(rcu_reader_qs_gp, 0);
 
        internal_urcu_lock();
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
        STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr + RCU_GP_CTR);
        wait_for_quiescent_state();
+       STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_ONGOING);
        internal_urcu_unlock();
 
        if (was_online)