sched: More sched_domain iterations fixes

sched_domain iterations needs to be protected by rcu_read_lock() now,
this patch adds another two places which needs the rcu lock, which is
spotted by following suspicious rcu_dereference_check() usage warnings.

kernel/sched_rt.c:1244 invoked rcu_dereference_check() without protection!
kernel/sched_stats.h:41 invoked rcu_dereference_check() without protection!

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1303469634-11678-1-git-send-email-dfeng@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 10 insertions, 4 deletions

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 64b2a37c07d0..88725c939e0b 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1263,6 +1263,7 @@ static int find_lowest_rq(struct task_struct *task)
         if (!cpumask_test_cpu(this_cpu, lowest_mask))
                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
 
+        rcu_read_lock();
         for_each_domain(cpu, sd) {
                 if (sd->flags & SD_WAKE_AFFINE) {
                         int best_cpu;
@@ -1272,15 +1273,20 @@ static int find_lowest_rq(struct task_struct *task)
                          * remote processor.
                          */
                         if (this_cpu != -1 &&
-                            cpumask_test_cpu(this_cpu, sched_domain_span(sd)))
+                            cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
+                                rcu_read_unlock();
                                 return this_cpu;
+                        }
 
                         best_cpu = cpumask_first_and(lowest_mask,
                                                      sched_domain_span(sd));
-                        if (best_cpu < nr_cpu_ids)
+                        if (best_cpu < nr_cpu_ids) {
+                                rcu_read_unlock();
                                 return best_cpu;
+                        }
                 }
         }
+        rcu_read_unlock();
 
         /*
          * And finally, if there were no matches within the domains
diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index 48ddf431db0e..331e01bcd026 100644
--- a/kernel/sched_stats.h
+++ b/kernel/sched_stats.h
@@ -37,7 +37,7 @@ static int show_schedstat(struct seq_file *seq, void *v)
 
 #ifdef CONFIG_SMP
                 /* domain-specific stats */
-                preempt_disable();
+                rcu_read_lock();
                 for_each_domain(cpu, sd) {
                         enum cpu_idle_type itype;
 
@@ -64,7 +64,7 @@ static int show_schedstat(struct seq_file *seq, void *v)
                             sd->ttwu_wake_remote, sd->ttwu_move_affine,
                             sd->ttwu_move_balance);
                 }
-                preempt_enable();
+                rcu_read_unlock();
 #endif
         }
         kfree(mask_str);