rcu: Shorten irq-disable region in rcu_cleanup_dead_cpu()

Now that we are not migrating callbacks, there is no need to hold the
->orphan_lock across the the ->qsmaskinit bit-clearing process.
This commit therefore releases ->orphan_lock immediately after adopting
the orphaned RCU callbacks.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 84f16cf05991c58d36293205569b9ef4a7dfbd75..990b406faf4e2e9fec8b45bbb512aaf08608930d 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2289,14 +2289,14 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
        /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
        rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
        rcu_adopt_orphan_cbs(rsp, flags);
+       raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
 
        /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
-       raw_spin_lock(&rnp->lock);      /* irqs already disabled. */
+       raw_spin_lock_irqsave(&rnp->lock, flags);
        smp_mb__after_unlock_lock();    /* Enforce GP memory-order guarantee. */
        rnp->qsmaskinit &= ~rdp->grpmask;
        if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
                rcu_cleanup_dead_rnp(rnp);
-       raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
        WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
                  "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",