Update email address from @polymtl.ca to @efficios.com

[urcu.git] / urcu-qsbr.c

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index c678d38779eb683f1f78872a87e853a4c281f43d..5e8b9603ae2f4c5f17efc6f8c54d9f1be9d9ccb0 100644 (file)
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -3,7 +3,7 @@
  *
  * Userspace RCU QSBR library
  *
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
  *
  * This library is free software; you can redistribute it and/or
@@ -121,10 +121,14 @@ static void update_counter_and_wait(void)
 #endif /* !(BITS_PER_LONG < 64) */
 
        /*
-        * Enforce compiler-order of store to rcu_gp_ctr before before
-        * load rcu_reader ctr.
-        * This ensures synchronize_rcu() cannot be starved by readers.
-        *
+        * Must commit rcu_gp_ctr update to memory before waiting for quiescent
+        * state. Failure to do so could result in the writer waiting forever
+        * while new readers are always accessing data (no progress). Enforce
+        * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr.
+        */
+       barrier();
+
+       /*
         * 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.
@@ -142,9 +146,9 @@ static void update_counter_and_wait(void)
                        smp_mb();
                }
 
-               list_for_each_entry_safe(index, tmp, &registry, head) {
+               list_for_each_entry_safe(index, tmp, &registry, node) {
                        if (!rcu_gp_ongoing(&index->ctr))
-                               list_move(&index->head, &qsreaders);
+                               list_move(&index->node, &qsreaders);
                }
 
                if (list_empty(&registry)) {
@@ -208,11 +212,12 @@ void synchronize_rcu(void)
 
        /*
         * 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.
+        * committing next rcu_gp_ctr update to memory. Failure to do so could
+        * result in the writer waiting forever while new readers are always
+        * accessing data (no progress).  Enforce compiler-order of load
+        * rcu_reader ctr before store to rcu_gp_ctr.
         */
+       barrier();
 
        /*
         * Adding a smp_mb() which is _not_ formally required, but makes the
@@ -300,7 +305,7 @@ void rcu_register_thread(void)
        assert(rcu_reader.ctr == 0);
 
        mutex_lock(&rcu_gp_lock);
-       list_add(&rcu_reader.head, &registry);
+       list_add(&rcu_reader.node, &registry);
        mutex_unlock(&rcu_gp_lock);
        _rcu_thread_online();
 }
@@ -313,7 +318,7 @@ void rcu_unregister_thread(void)
         */
        _rcu_thread_offline();
        mutex_lock(&rcu_gp_lock);
-       list_del(&rcu_reader.head);
+       list_del(&rcu_reader.node);
        mutex_unlock(&rcu_gp_lock);
 }