rcu: use irq-safe locks

Some earlier tip/core/rcu patches caused RCU to incorrectly enable irqs
too early in boot.  This caused Yinghai's repeated-kexec testing to
hit oopses, presumably due to so that device interrupts left over from
the prior kernel instance (which would oops the newly booting kernel
before it got a chance to reset said devices).  This patch therefore
converts all the local_irq_disable()s in rcuclassic.c to local_irq_save().

Besides, I never did like local_irq_disable() anyway.  ;-)

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 6 deletions

diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index 01e761a6b38c..3f6918966bda 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -247,6 +247,7 @@ static inline void raise_rcu_softirq(void)
  */
 static void rcu_do_batch(struct rcu_data *rdp)
 {
+        unsigned long flags;
         struct rcu_head *next, *list;
         int count = 0;
 
@@ -261,9 +262,9 @@ static void rcu_do_batch(struct rcu_data *rdp)
         }
         rdp->donelist = list;
 
-        local_irq_disable();
+        local_irq_save(flags);
         rdp->qlen -= count;
-        local_irq_enable();
+        local_irq_restore(flags);
         if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
                 rdp->blimit = blimit;
 
@@ -464,12 +465,14 @@ static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
 static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
                                 struct rcu_head **tail, long batch)
 {
+        unsigned long flags;
+
         if (list) {
-                local_irq_disable();
+                local_irq_save(flags);
                 this_rdp->batch = batch;
                 *this_rdp->nxttail[2] = list;
                 this_rdp->nxttail[2] = tail;
-                local_irq_enable();
+                local_irq_restore(flags);
         }
 }
 
@@ -521,10 +524,11 @@ static void rcu_offline_cpu(int cpu)
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
                                         struct rcu_data *rdp)
 {
+        unsigned long flags;
         long completed_snap;
 
         if (rdp->nxtlist) {
-                local_irq_disable();
+                local_irq_save(flags);
                 completed_snap = ACCESS_ONCE(rcp->completed);
 
                 /*
@@ -554,7 +558,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
                         rdp->nxttail[0] = &rdp->nxtlist;
                 }
 
-                local_irq_enable();
+                local_irq_restore(flags);
 
                 if (rcu_batch_after(rdp->batch, rcp->pending)) {
                         unsigned long flags;