sched: convert rebalance_domains() 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, 8 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 154a95fcea7e..67383e7f1ccd 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3850,7 +3850,11 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle)
         unsigned long next_balance = jiffies + 60*HZ;
         int update_next_balance = 0;
         int need_serialize;
-        cpumask_t tmp;
+        cpumask_var_t tmp;
+
+        /* Fails alloc?  Rebalancing probably not a priority right now. */
+        if (!alloc_cpumask_var(&tmp, GFP_ATOMIC))
+                return;
 
         for_each_domain(cpu, sd) {
                 if (!(sd->flags & SD_LOAD_BALANCE))
@@ -3875,7 +3879,7 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle)
                 }
 
                 if (time_after_eq(jiffies, sd->last_balance + interval)) {
-                        if (load_balance(cpu, rq, sd, idle, &balance, &tmp)) {
+                        if (load_balance(cpu, rq, sd, idle, &balance, tmp)) {
                                 /*
                                  * We've pulled tasks over so either we're no
                                  * longer idle, or one of our SMT siblings is
@@ -3909,6 +3913,8 @@ out:
          */
         if (likely(update_next_balance))
                 rq->next_balance = next_balance;
+
+        free_cpumask_var(tmp);
 }
 
 /*