sched: Remove unnecessary RCU exclusion

commit fb58bac5c75bfff8bbf7d02071a10a62f32fe28b upstream

As Nick pointed out, and realized by myself when doing:
   sched: Fix balance vs hotplug race
the patch:
   sched: for_each_domain() vs RCU

is wrong, sched_domains are freed after synchronize_sched(), which
means disabling preemption is enough.

Reported-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index be3450816f9eb4c8556e5ee69d7abc1412a0dee5..d2c46e761fcd72edb6221e0e5415d55da3772079 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1410,7 +1410,6 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
                new_cpu = prev_cpu;
        }
 
-       rcu_read_lock();
        for_each_domain(cpu, tmp) {
                if (!(tmp->flags & SD_LOAD_BALANCE))
                        continue;
@@ -1500,10 +1499,8 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
                }
        }
 
-       if (affine_sd && wake_affine(affine_sd, p, sync)) {
-               new_cpu = cpu;
-               goto out;
-       }
+       if (affine_sd && wake_affine(affine_sd, p, sync))
+               return cpu;
 
        while (sd) {
                int load_idx = sd->forkexec_idx;
@@ -1544,8 +1541,6 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
                /* while loop will break here if sd == NULL */
        }
 
-out:
-       rcu_read_unlock();
        return new_cpu;
 }
 #endif /* CONFIG_SMP */