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Subject[PATCH] Fix hibernate/resume in presence of PREEMPT_RCU and hotplug
Hello!

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>
---

rcupreempt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff -urpNa -X dontdiff linux-2.6.25-rc3/kernel/rcupreempt.c linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c
--- linux-2.6.25-rc3/kernel/rcupreempt.c 2008-02-26 16:58:43.000000000 -0800
+++ linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c 2008-02-26 17:04:17.000000000 -0800
@@ -702,8 +702,9 @@ 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;

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