From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Thu, 28 Feb 2008 00:21:10 +0000 (-0800)
Subject: rcupreempt: fix hibernate/resume in presence of PREEMPT_RCU and hotplug
X-Git-Tag: v2.6.25-rc4~130
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ae778869ae4549628b9e83efe958c3aaa63ed1b9;p=linux-2.6

rcupreempt: fix hibernate/resume in presence of PREEMPT_RCU and hotplug

This fixes a oops encountered when doing hibernate/resume in presence of
PREEMPT_RCU.

The problem was that the code failed to disable preemption when
accessing a per-CPU variable.  This is OK when called from code that
already has preemption disabled, but such is not the case from the
suspend/resume code path.

Reported-by: Dave Young <hidave.darkstar@gmail.com>
Tested-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index c7c52096df..845abcd472 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -918,8 +918,9 @@ void rcu_offline_cpu(int cpu)
 	 * fix.
 	 */
 
+	local_irq_save(flags);
 	rdp = RCU_DATA_ME();
-	spin_lock_irqsave(&rdp->lock, flags);
+	spin_lock(&rdp->lock);
 	*rdp->nexttail = list;
 	if (list)
 		rdp->nexttail = tail;