3 files changed, 45 insertions, 9 deletions

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 61fef37..a946176 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -283,6 +283,43 @@ do {						\
 })
 
 /*
+ * Locks two spinlocks l1 and l2.
+ * l1_first indicates if spinlock l1 should be taken first.
+ */
+static inline void double_spin_lock(spinlock_t *l1, spinlock_t *l2,
+				    bool l1_first)
+	__acquires(l1)
+	__acquires(l2)
+{
+	if (l1_first) {
+		spin_lock(l1);
+		spin_lock(l2);
+	} else {
+		spin_lock(l2);
+		spin_lock(l1);
+	}
+}
+
+/*
+ * Unlocks two spinlocks l1 and l2.
+ * l1_taken_first indicates if spinlock l1 was taken first and therefore
+ * should be released after spinlock l2.
+ */
+static inline void double_spin_unlock(spinlock_t *l1, spinlock_t *l2,
+				      bool l1_taken_first)
+	__releases(l1)
+	__releases(l2)
+{
+	if (l1_taken_first) {
+		spin_unlock(l2);
+		spin_unlock(l1);
+	} else {
+		spin_unlock(l1);
+		spin_unlock(l2);
+	}
+}
+
+/*
  * Pull the atomic_t declaration:
  * (asm-mips/atomic.h needs above definitions)
  */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 476cb0c..de93a81 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1355,17 +1355,16 @@ static void migrate_hrtimers(int cpu)
 	tick_cancel_sched_timer(cpu);
 
 	local_irq_disable();
-
-	spin_lock(&new_base->lock);
-	spin_lock(&old_base->lock);
+	double_spin_lock(&new_base->lock, &old_base->lock,
+			 smp_processor_id() < cpu);
 
 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
 		migrate_hrtimer_list(&old_base->clock_base[i],
 				     &new_base->clock_base[i]);
 	}
-	spin_unlock(&old_base->lock);
-	spin_unlock(&new_base->lock);
 
+	double_spin_unlock(&new_base->lock, &old_base->lock,
+			   smp_processor_id() < cpu);
 	local_irq_enable();
 	put_cpu_var(hrtimer_bases);
 }
diff --git a/kernel/timer.c b/kernel/timer.c
index 6663a87..8ad3842 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1651,8 +1651,8 @@ static void __devinit migrate_timers(int cpu)
 	new_base = get_cpu_var(tvec_bases);
 
 	local_irq_disable();
-	spin_lock(&new_base->lock);
-	spin_lock(&old_base->lock);
+	double_spin_lock(&new_base->lock, &old_base->lock,
+			 smp_processor_id() < cpu);
 
 	BUG_ON(old_base->running_timer);
 
@@ -1665,8 +1665,8 @@ static void __devinit migrate_timers(int cpu)
 		migrate_timer_list(new_base, old_base->tv5.vec + i);
 	}
 
-	spin_unlock(&old_base->lock);
-	spin_unlock(&new_base->lock);
+	double_spin_unlock(&new_base->lock, &old_base->lock,
+			   smp_processor_id() < cpu);
 	local_irq_enable();
 	put_cpu_var(tvec_bases);
 }