sched: convert idle_balance() to cpumask_var_t.

Impact: stack usage reduction

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
space in the stack.  cpumask_var_t is just a struct cpumask for
!CONFIG_CPUMASK_OFFSTACK.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 2f8ea99df16a..154a95fcea7e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3676,7 +3676,10 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
         struct sched_domain *sd;
         int pulled_task = -1;
         unsigned long next_balance = jiffies + HZ;
-        cpumask_t tmpmask;
+        cpumask_var_t tmpmask;
+
+        if (!alloc_cpumask_var(&tmpmask, GFP_ATOMIC))
+                return;
 
         for_each_domain(this_cpu, sd) {
                 unsigned long interval;
@@ -3687,7 +3690,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                 if (sd->flags & SD_BALANCE_NEWIDLE)
                         /* If we've pulled tasks over stop searching: */
                         pulled_task = load_balance_newidle(this_cpu, this_rq,
-                                                           sd, &tmpmask);
+                                                           sd, tmpmask);
 
                 interval = msecs_to_jiffies(sd->balance_interval);
                 if (time_after(next_balance, sd->last_balance + interval))
@@ -3702,6 +3705,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                  */
                 this_rq->next_balance = next_balance;
         }
+        free_cpumask_var(tmpmask);
 }
 
 /*