aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/rcutree_plugin.h
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-19 19:57:45 -0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-20 12:00:17 -0400
commit80dcf60e6b97c7363971e7a0a788d8484d35f8a6 (patch)
tree2f493fdf6a7a52675733ac74daa9e1cd9342a030 /kernel/rcutree_plugin.h
parent7b0b759b65247cbc66384a912be9acf8d4800636 (diff)
rcu: apply TINY_PREEMPT_RCU read-side speedup to TREE_PREEMPT_RCU
Replace one of the ACCESS_ONCE() calls in each of __rcu_read_lock() and __rcu_read_unlock() with barrier() as suggested by Steve Rostedt in order to avoid the potential compiler-optimization-induced bug noted by Mathieu Desnoyers. Located-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r--kernel/rcutree_plugin.h6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 87f60f06b18e..e9e0bc74ff37 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -201,7 +201,7 @@ static void rcu_preempt_note_context_switch(int cpu)
201 */ 201 */
202void __rcu_read_lock(void) 202void __rcu_read_lock(void)
203{ 203{
204 ACCESS_ONCE(current->rcu_read_lock_nesting)++; 204 current->rcu_read_lock_nesting++;
205 barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ 205 barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */
206} 206}
207EXPORT_SYMBOL_GPL(__rcu_read_lock); 207EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -344,7 +344,9 @@ void __rcu_read_unlock(void)
344 struct task_struct *t = current; 344 struct task_struct *t = current;
345 345
346 barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ 346 barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */
347 if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 && 347 --t->rcu_read_lock_nesting;
348 barrier(); /* decrement before load of ->rcu_read_unlock_special */
349 if (t->rcu_read_lock_nesting == 0 &&
348 unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) 350 unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
349 rcu_read_unlock_special(t); 351 rcu_read_unlock_special(t);
350#ifdef CONFIG_PROVE_LOCKING 352#ifdef CONFIG_PROVE_LOCKING