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Commit 886ef5a1 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 1de6e56d

kernel/rcu/tree.c

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