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rcu: Move smp_mb() from rcu_seq_snap() to rcu_exp_gp_seq_snap()

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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@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2015-09-29 12:34:40 -07:00
parent 1de6e56ddc
commit 886ef5a18a
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tree.c
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@@ -3347,7 +3347,6 @@ static unsigned long rcu_seq_snap(unsigned long *sp)
{ {
unsigned long s; unsigned long s;
smp_mb(); /* Caller's modifications seen first by other CPUs. */
s = (READ_ONCE(*sp) + 3) & ~0x1; s = (READ_ONCE(*sp) + 3) & ~0x1;
smp_mb(); /* Above access must not bleed into critical section. */ smp_mb(); /* Above access must not bleed into critical section. */
return s; 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) 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); return rcu_seq_snap(&rsp->expedited_sequence);
} }
static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s) static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)