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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-15 02:24:14 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-23 01:27:43 +0300 |
| commit | 9a54f98e341d09793247a6e598012edefb5ae7cb (patch) | |
| tree | 4a30b36698274e22b17651a0cad70500af2cef21 /kernel/rcu | |
| parent | 3ad81779ad35cd2e2ab34ba3f47f6f485696a105 (diff) | |
| download | linux-9a54f98e341d09793247a6e598012edefb5ae7cb.tar.xz | |
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 <marcin.slusarz@gmail.com>
Reported-by: David Rientjes <rientjes@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Tested-by: Marcin Ślusarz <marcin.slusarz@gmail.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2 |
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); cond_resched_rcu_qs(); } - put_online_cpus(); /* Unconditionally decrement: no need to wake ourselves up. */ atomic_dec(&oom_callback_count); |