X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=5e8b9603ae2f4c5f17efc6f8c54d9f1be9d9ccb0;hp=c678d38779eb683f1f78872a87e853a4c281f43d;hb=6982d6d71aeed16d2d929bd0ed221e8f444b706e;hpb=935b11ff4cf9053954d21b9d63c4ee367b12a652

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index c678d38..5e8b960 100644
--- 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);
 }