sched: for_each_domain() vs RCU
for_each_domain() uses RCU to serialize the sched_domains, except
it doesn't actually use rcu_read_lock() and instead relies on
disabling preemption -> FAIL.
XXX: audit other sched_domain code.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index eaa0001..43dc6d1 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1331,6 +1331,7 @@
new_cpu = prev_cpu;
}
+ rcu_read_lock();
for_each_domain(cpu, tmp) {
/*
* If power savings logic is enabled for a domain, see if we
@@ -1369,8 +1370,10 @@
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
- if (wake_affine(tmp, p, sync))
- return cpu;
+ if (wake_affine(tmp, p, sync)) {
+ new_cpu = cpu;
+ goto out;
+ }
want_affine = 0;
}
@@ -1416,6 +1419,8 @@
/* while loop will break here if sd == NULL */
}
+out:
+ rcu_read_unlock();
return new_cpu;
}
#endif /* CONFIG_SMP */