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authorPaul E. McKenney <paulmck@kernel.org>2021-02-26 11:25:29 -0800
committerPaul E. McKenney <paulmck@kernel.org>2021-03-15 13:53:24 -0700
commit7e937220afa3eada0d4611b31e4e3c60770e39b4 (patch)
tree3e5f1785dbab114fc34d174e6dfd79bfc0615f6c /kernel/rcu
parente589c7c72315f7e52ebb5cffc19615dc18d0cc50 (diff)
rcu: Add explicit barrier() to __rcu_read_unlock()
Because preemptible RCU's __rcu_read_unlock() is an external function, the rough equivalent of an implicit barrier() is inserted by the compiler. Except that there is a direct call to __rcu_read_unlock() in that same file, and compilers are getting to the point where they might choose to inline the fastpath of the __rcu_read_unlock() function. This commit therefore adds an explicit barrier() to the very beginning of __rcu_read_unlock(). Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree_plugin.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2d603771c7dc..a32494c4b6f6 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -393,8 +393,9 @@ void __rcu_read_unlock(void)
{
struct task_struct *t = current;
+ barrier(); // critical section before exit code.
if (rcu_preempt_read_exit() == 0) {
- barrier(); /* critical section before exit code. */
+ barrier(); // critical-section exit before .s check.
if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
}