On Wed, Nov 29, 2017 at 11:51:51AM +1100, Stephen Rothwell wrote:

quoted

Hi Paul,

Commit

  d7e182c9c324 ("rcu: Remove unnecessary spinlock in rcu_boot_init_percpu_data()")

is missing a Signed-off-by from its author.

Good catch, Stephen!

Lihao, would you please get me you Signed-off-by?  The patch is below.

							Thanx, Paul

------------------------------------------------------------------------

commit d7e182c9c32480c1f579dd888ac50e88bfb39596
Author: Liang Lihao [off-list ref]
Date:   Wed Nov 22 19:00:55 2017 +0000

    rcu: Remove unnecessary spinlock in rcu_boot_init_percpu_data()
    
    Since rcu_boot_init_percpu_data() is only called at boot time,
    there is no data race and spinlock is not needed.
    
    Signed-off-by: Paul E. McKenney [off-list ref]

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 69722817d6d6..0abe1db53d70 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c

@@ -3636,12 +3636,9 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
 static void __init
 rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 {
-	unsigned long flags;
 	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
-	struct rcu_node *rnp = rcu_get_root(rsp);
 
 	/* Set up local state, ensuring consistent view of global state. */
-	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
 	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
 	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != 1);

@@ -3649,7 +3646,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 	rdp->cpu = cpu;
 	rdp->rsp = rsp;
 	rcu_boot_init_nocb_percpu_data(rdp);
-	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 }
 
 /*