[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>

1 files changed, 6 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index b5b350135002..d327511d268e 100644
--- a/kernel/sched.c
+++ b/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);