Internal cleanup

[urcu.git] / urcu-bp.c

diff --git a/urcu-bp.c b/urcu-bp.c
index eda000539b19b01ce582fe098be1d1cc0f1a3b3f..fc6eedf56a545dde91e1fa8b96456af5bc593158 100644 (file)
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -116,22 +116,29 @@ static void mutex_unlock(pthread_mutex_t *mutex)
        }
 }
 
-/*
- * called with rcu_gp_lock held.
- */
-static void switch_next_rcu_qparity(void)
-{
-       STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
-}
-
-void wait_for_quiescent_state(void)
+void update_counter_and_wait(void)
 {
        LIST_HEAD(qsreaders);
        int wait_loops = 0;
        struct rcu_reader *index, *tmp;
 
-       if (list_empty(&registry))
-               return;
+       /* Switch parity: 1 -> 0, 0 -> 1 */
+       STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
+
+       /*
+        * Must commit qparity update to memory before waiting for other parity
+        * quiescent state. Failure to do so could result in the writer waiting
+        * forever while new readers are always accessing data (no progress).
+        * Ensured by STORE_SHARED and LOAD_SHARED.
+        */
+
+       /*
+        * Adding a smp_mb() which is _not_ formally required, but makes the
+        * model easier to understand. It does not have a big performance impact
+        * anyway, given this is the write-side.
+        */
+       smp_mb();
+
        /*
         * Wait for each thread rcu_reader.ctr count to become 0.
         */
@@ -167,44 +174,21 @@ void synchronize_rcu(void)
 
        mutex_lock(&rcu_gp_lock);
 
-       /* Remove old registry elements */
-       rcu_gc_registry();
+       if (list_empty(&registry))
+               goto out;
 
        /* All threads should read qparity before accessing data structure
-        * where new ptr points to. Must be done within rcu_gp_lock because it
-        * iterates on reader threads.*/
+        * where new ptr points to. */
        /* Write new ptr before changing the qparity */
        smp_mb();
 
-       switch_next_rcu_qparity();      /* 0 -> 1 */
-
-       /*
-        * Must commit qparity update to memory before waiting for parity
-        * 0 quiescent state. Failure to do so could result in the writer
-        * waiting forever while new readers are always accessing data (no
-        * progress).
-        * Ensured by STORE_SHARED and LOAD_SHARED.
-        */
-
-       /*
-        * Adding a smp_mb() which is _not_ formally required, but makes the
-        * model easier to understand. It does not have a big performance impact
-        * anyway, given this is the write-side.
-        */
-       smp_mb();
+       /* Remove old registry elements */
+       rcu_gc_registry();
 
        /*
         * Wait for previous parity to be empty of readers.
         */
-       wait_for_quiescent_state();     /* Wait readers in parity 0 */
-
-       /*
-        * Must finish waiting for quiescent state for parity 0 before
-        * committing qparity update to memory. Failure to do so could result in
-        * the writer waiting forever while new readers are always accessing
-        * data (no progress).
-        * Ensured by STORE_SHARED and LOAD_SHARED.
-        */
+       update_counter_and_wait();      /* 0 -> 1, wait readers in parity 0 */
 
        /*
         * Adding a smp_mb() which is _not_ formally required, but makes the
@@ -213,33 +197,17 @@ void synchronize_rcu(void)
         */
        smp_mb();
 
-       switch_next_rcu_qparity();      /* 1 -> 0 */
-
        /*
-        * Must commit qparity update to memory before waiting for parity
-        * 1 quiescent state. Failure to do so could result in the writer
-        * waiting forever while new readers are always accessing data (no
-        * progress).
-        * Ensured by STORE_SHARED and LOAD_SHARED.
-        */
-
-       /*
-        * Adding a smp_mb() which is _not_ formally required, but makes the
-        * model easier to understand. It does not have a big performance impact
-        * anyway, given this is the write-side.
+        * Wait for previous parity to be empty of readers.
         */
-       smp_mb();
+       update_counter_and_wait();      /* 1 -> 0, wait readers in parity 1 */
 
        /*
-        * Wait for previous parity to be empty of readers.
+        * Finish waiting for reader threads before letting the old ptr being
+        * freed.
         */
-       wait_for_quiescent_state();     /* Wait readers in parity 1 */
-
-       /* Finish waiting for reader threads before letting the old ptr being
-        * freed. Must be done within rcu_gp_lock because it iterates on reader
-        * threads. */
        smp_mb();
-
+out:
        mutex_unlock(&rcu_gp_lock);
        ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
        assert(!ret);