Internal cleanup

[urcu.git] / urcu.c

diff --git a/urcu.c b/urcu.c
index 6e9589145cf789a06c00aa988cb01d8c3dcb27fa..e93170d749b4c939884840767febcc3e3d820997 100644 (file)
--- a/urcu.c
+++ b/urcu.c
@@ -120,14 +120,6 @@ 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);
-}
-
 #ifdef RCU_MEMBARRIER
 static void smp_mb_heavy(void)
 {
@@ -207,14 +199,29 @@ static void wait_gp(void)
                      NULL, NULL, 0);
 }
 
-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.
         */
@@ -280,33 +287,19 @@ void synchronize_rcu(void)
 {
        mutex_lock(&rcu_gp_lock);
 
+       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.*/
        /* Write new ptr before changing the qparity */
        smp_mb_heavy();
 
-       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();
-
        /*
         * Wait for previous parity to be empty of readers.
         */
-       wait_for_quiescent_state();     /* Wait readers in parity 0 */
+       update_counter_and_wait();      /* 0 -> 1, wait readers in parity 0 */
 
        /*
         * Must finish waiting for quiescent state for parity 0 before
@@ -323,33 +316,16 @@ 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.
-        */
-       smp_mb();
-
        /*
         * Wait for previous parity to be empty of readers.
         */
-       wait_for_quiescent_state();     /* Wait readers in parity 1 */
+       update_counter_and_wait();      /* 1 -> 0, 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_heavy();
-
+out:
        mutex_unlock(&rcu_gp_lock);
 }