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>

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 954e1a8..da932f4 100644 (file)
--- 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);
        }
 
        /*