Commit 7e937220 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@kernel.org>
parent e589c7c7

kernel/rcu/tree_plugin.h

+2 −1
Original line number Diff line number Diff line
@@ -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);

	}