[PATCH] cpuset: skip rcu check if task is in root cpuset

[pandora-kernel.git] / kernel / cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 681a5d5..e04c2da 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -647,10 +647,15 @@ void cpuset_update_task_memory_state()
        struct task_struct *tsk = current;
        struct cpuset *cs;
 
-       rcu_read_lock();
-       cs = rcu_dereference(tsk->cpuset);
-       my_cpusets_mem_gen = cs->mems_generation;
-       rcu_read_unlock();
+       if (tsk->cpuset == &top_cpuset) {
+               /* Don't need rcu for top_cpuset.  It's never freed. */
+               my_cpusets_mem_gen = top_cpuset.mems_generation;
+       } else {
+               rcu_read_lock();
+               cs = rcu_dereference(tsk->cpuset);
+               my_cpusets_mem_gen = cs->mems_generation;
+               rcu_read_unlock();
+       }
 
        if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
                down(&callback_sem);