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>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index c7c52096df48..845abcd472b0 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;