[PATCH tip/core/rcu 5/9] rcu: Correctly initialize ->rcu_qs_ctr_snap at online time

From: Paul E. McKenney
Date: Tue May 12 2015 - 17:50:33 EST

From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

The rcu_data structure's ->rcu_qs_ctr_snap field is initialized at
CPU-online time from the current CPU's element of the per-CPU rcu_qs_ctr
variable. Unfortunately, this is at CPU_UP_PREPARE time, so has nothing
to do with the CPU being onlined. This commit therefore initializes
this variable from the incoming CPU's element of rcu_qs_ctr.

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 1eb1029a5464..48d002d4faac 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3761,7 +3761,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
rdp->completed = rnp->completed;
rdp->passed_quiesce = false;
- rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
+ rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu);
rdp->qs_pending = false;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
raw_spin_unlock_irqrestore(&rnp->lock, flags);

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