Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6206ab9b authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

rcu: Move __rcu_read_unlock()'s barrier() within if-statement 



We only need to constrain the compiler if we are actually exiting
the top-level RCU read-side critical section.  This commit therefore
moves the first barrier() cal in __rcu_read_unlock() to inside the
"if" statement, thus avoiding needless register flushes for inner
rcu_read_unlock() calls.

Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 6846c0c5

include/linux/rcupdate.h

+2 −12
Original line number Diff line number Diff line
@@ -134,16 +134,6 @@ extern void call_rcu_sched(struct rcu_head *head, 


extern void synchronize_sched(void);



static inline void __rcu_read_lock_bh(void)

{

	local_bh_disable();

}



static inline void __rcu_read_unlock_bh(void)

{

	local_bh_enable();

}



#ifdef CONFIG_PREEMPT_RCU



extern void __rcu_read_lock(void);
@@ -686,7 +676,7 @@ static inline void rcu_read_unlock(void) 
 */

static inline void rcu_read_lock_bh(void)

{

	__rcu_read_lock_bh();

	local_bh_disable();

	__acquire(RCU_BH);

	rcu_read_acquire_bh();

}
@@ -700,7 +690,7 @@ static inline void rcu_read_unlock_bh(void) 
{

	rcu_read_release_bh();

	__release(RCU_BH);

	__rcu_read_unlock_bh();

	local_bh_enable();

}



/**

kernel/rcutree_plugin.h

+1 −1
Original line number Diff line number Diff line
@@ -415,10 +415,10 @@ void __rcu_read_unlock(void) 
{

	struct task_struct *t = current;



	barrier();  /* needed if we ever invoke rcu_read_unlock in rcutree.c */

	if (t->rcu_read_lock_nesting != 1)

		--t->rcu_read_lock_nesting;

	else {

		barrier();  /* critical section before exit code. */

		t->rcu_read_lock_nesting = INT_MIN;

		barrier();  /* assign before ->rcu_read_unlock_special load */

		if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))