On Tue, 14 Jul 2015, Paul E. McKenney wrote: > commit a1992f2f3b8e174d740a8f764d0d51344bed2eed > Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > Date: Tue Jul 14 16:24:14 2015 -0700 > > 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@xxxxxxxxx> > Reported-by: David Rientjes <rientjes@xxxxxxxxxx> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>