linux-kernel - [PATCH tip/core/rcu 07/10] rcu: Shorten irq-disable region in rcu_cleanup_dead

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Date:	Wed,  5 Nov 2014 09:41:31 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 07/10] rcu: Shorten irq-disable region in rcu_cleanup_dead_cpu()

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

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@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e870b0f5e1b9..3c23e921b438 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2257,14 +2257,14 @@ 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",
-- 
1.8.1.5

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