Commit-ID: 886ef5a18a4a771d5fdc0e23ae9373bb35d529e7
Gitweb: http://git.kernel.org/tip/886ef5a18a4a771d5fdc0e23ae9373bb35d529e7
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 29 Sep 2015 12:34:40 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Fri, 4 Dec 2015 12:26:51 -0800
rcu: Move smp_mb() from rcu_seq_snap() to rcu_exp_gp_seq_snap()
The memory barrier in rcu_seq_snap() is needed only for grace periods,
so this commit moves it to the grace-period-oriented wrapper
rcu_exp_gp_seq_snap().
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index bd2605c..a4a0475 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3347,7 +3347,6 @@ static unsigned long rcu_seq_snap(unsigned long *sp)
{
unsigned long s;
- smp_mb(); /* Caller's modifications seen first by other CPUs. */
s = (READ_ONCE(*sp) + 3) & ~0x1;
smp_mb(); /* Above access must not bleed into critical section. */
return s;
@@ -3374,6 +3373,7 @@ static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
}
static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
{
+ smp_mb(); /* Caller's modifications seen first by other CPUs. */
return rcu_seq_snap(&rsp->expedited_sequence);
}
static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
--
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