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Subject[103/123] sched: Remove unnecessary RCU exclusion
From: Peter Zijlstra <a.p.zijlstra@chello.nl>

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>
---
kernel/sched_fair.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1410,7 +1410,6 @@ select_task_rq_fair(struct rq *rq, struc
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, struc
}
}

- 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, struc
/* while loop will break here if sd == NULL */
}

-out:
- rcu_read_unlock();
return new_cpu;
}
#endif /* CONFIG_SMP */



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