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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-08-20 01:57:45 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-08-20 18:00:17 +0200 |
| commit | 80dcf60e6b97c7363971e7a0a788d8484d35f8a6 (patch) | |
| tree | 2f493fdf6a7a52675733ac74daa9e1cd9342a030 | |
| parent | rcu: combine duplicate code, courtesy of CONFIG_PREEMPT_RCU (diff) | |
| download | linux-80dcf60e6b97c7363971e7a0a788d8484d35f8a6.tar.xz linux-80dcf60e6b97c7363971e7a0a788d8484d35f8a6.zip | |
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>
| -rw-r--r-- | kernel/rcutree_plugin.h | 6 |
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) */ void __rcu_read_lock(void) { - ACCESS_ONCE(current->rcu_read_lock_nesting)++; + current->rcu_read_lock_nesting++; barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ } EXPORT_SYMBOL_GPL(__rcu_read_lock); @@ -344,7 +344,9 @@ void __rcu_read_unlock(void) struct task_struct *t = current; barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ - if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 && + --t->rcu_read_lock_nesting; + barrier(); /* decrement before load of ->rcu_read_unlock_special */ + if (t->rcu_read_lock_nesting == 0 && unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) rcu_read_unlock_special(t); #ifdef CONFIG_PROVE_LOCKING |