[PATCH] sched: disable interrupts for locking in load_balance()

Interrupts must be disabled for request queue locks if we want to run
load_balance() with interrupts enabled.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sched.c

@@ -2546,8 +2546,6 @@ static inline unsigned long minus_1_or_zero(unsigned long n)
 /*
  * Check this_cpu to ensure it is balanced within domain. Attempt to move
  * tasks if there is an imbalance.
- *
- * Called with this_rq unlocked.
  */
 static int load_balance(int this_cpu, struct rq *this_rq,
 			struct sched_domain *sd, enum idle_type idle)
@@ -2557,6 +2555,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 	unsigned long imbalance;
 	struct rq *busiest;
 	cpumask_t cpus = CPU_MASK_ALL;
+	unsigned long flags;
 
 	/*
 	 * When power savings policy is enabled for the parent domain, idle
@@ -2596,11 +2595,13 @@ redo:
 		 * still unbalanced. nr_moved simply stays zero, so it is
 		 * correctly treated as an imbalance.
 		 */
+		local_irq_save(flags);
 		double_rq_lock(this_rq, busiest);
 		nr_moved = move_tasks(this_rq, this_cpu, busiest,
 				      minus_1_or_zero(busiest->nr_running),
 				      imbalance, sd, idle, &all_pinned);
 		double_rq_unlock(this_rq, busiest);
+		local_irq_restore(flags);
 
 		/* All tasks on this runqueue were pinned by CPU affinity */
 		if (unlikely(all_pinned)) {
@@ -2617,13 +2618,13 @@ redo:
 
 		if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
 
-			spin_lock(&busiest->lock);
+			spin_lock_irqsave(&busiest->lock, flags);
 
 			/* don't kick the migration_thread, if the curr
 			 * task on busiest cpu can't be moved to this_cpu
 			 */
 			if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
-				spin_unlock(&busiest->lock);
+				spin_unlock_irqrestore(&busiest->lock, flags);
 				all_pinned = 1;
 				goto out_one_pinned;
 			}
@@ -2633,7 +2634,7 @@ redo:
 				busiest->push_cpu = this_cpu;
 				active_balance = 1;
 			}
-			spin_unlock(&busiest->lock);
+			spin_unlock_irqrestore(&busiest->lock, flags);
 			if (active_balance)
 				wake_up_process(busiest->migration_thread);