cpumask: reduce stack usage in find_lowest_rq

Impact: reduce stack usage, cleanup

Use a cpumask_var_t in find_lowest_rq() and clean up other old
cpumask_t calls.

Signed-off-by: Mike Travis <travis@sgi.com>

1 files changed, 22 insertions, 14 deletions

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 954e1a81b796..da932f4c8524 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -960,16 +960,17 @@ static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
 
-static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
+static inline int pick_optimal_cpu(int this_cpu,
+                                   const struct cpumask *mask)
 {
         int first;
 
         /* "this_cpu" is cheaper to preempt than a remote processor */
-        if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
+        if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
                 return this_cpu;
 
-        first = first_cpu(*mask);
-        if (first != NR_CPUS)
+        first = cpumask_first(mask);
+        if (first < nr_cpu_ids)
                 return first;
 
         return -1;
@@ -981,6 +982,7 @@ static int find_lowest_rq(struct task_struct *task)
         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
         int this_cpu = smp_processor_id();
         int cpu      = task_cpu(task);
+        cpumask_var_t domain_mask;
 
         if (task->rt.nr_cpus_allowed == 1)
                 return -1; /* No other targets possible */
@@ -1013,19 +1015,25 @@ static int find_lowest_rq(struct task_struct *task)
         if (this_cpu == cpu)
                 this_cpu = -1; /* Skip this_cpu opt if the same */
 
-        for_each_domain(cpu, sd) {
-                if (sd->flags & SD_WAKE_AFFINE) {
-                        cpumask_t domain_mask;
-                        int       best_cpu;
+        if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
+                for_each_domain(cpu, sd) {
+                        if (sd->flags & SD_WAKE_AFFINE) {
+                                int best_cpu;
 
-                        cpumask_and(&domain_mask, sched_domain_span(sd),
-                                    lowest_mask);
+                                cpumask_and(domain_mask,
+                                            sched_domain_span(sd),
+                                            lowest_mask);
 
-                        best_cpu = pick_optimal_cpu(this_cpu,
-                                                    &domain_mask);
-                        if (best_cpu != -1)
-                                return best_cpu;
+                                best_cpu = pick_optimal_cpu(this_cpu,
+                                                            domain_mask);
+
+                                if (best_cpu != -1) {
+                                        free_cpumask_var(domain_mask);
+                                        return best_cpu;
+                                }
+                        }
                 }
+                free_cpumask_var(domain_mask);
         }
 
         /*