diff options
authorPaul E. McKenney <>2015-07-14 16:24:14 -0700
committerPaul E. McKenney <>2015-07-22 15:27:43 -0700
commit9a54f98e341d09793247a6e598012edefb5ae7cb (patch)
parent3ad81779ad35cd2e2ab34ba3f47f6f485696a105 (diff)
rcu: Don't disable CPU hotplug during OOM notifiers
RCU's rcu_oom_notify() disables CPU hotplug in order to stabilize the list of online CPUs, which it traverses. However, this is completely pointless because smp_call_function_single() will quietly fail if invoked on an offline CPU. Because the count of requests is incremented in the rcu_oom_notify_cpu() function that is remotely invoked, everything works nicely even in the face of concurrent CPU-hotplug operations. Furthermore, in recent kernels, invoking get_online_cpus() from an OOM notifier can result in deadlock. This commit therefore removes the call to get_online_cpus() and put_online_cpus() from rcu_oom_notify(). Reported-by: Marcin Ślusarz <> Reported-by: David Rientjes <> Signed-off-by: Paul E. McKenney <> Acked-by: David Rientjes <> Tested-by: Marcin Ślusarz <>
1 files changed, 0 insertions, 2 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 9e922f111d63..80a7c17907fe 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1679,12 +1679,10 @@ static int rcu_oom_notify(struct notifier_block *self,
atomic_set(&oom_callback_count, 1);
- get_online_cpus();
for_each_online_cpu(cpu) {
smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
- put_online_cpus();
/* Unconditionally decrement: no need to wake ourselves up. */