Re: cpu_hotplug vs oom_notify_list: possible circular locking dependency detected

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Tue, Jul 14, 2015 at 04:48:24PM -0700, David Rientjes wrote:
> On Tue, 14 Jul 2015, Paul E. McKenney wrote:
> 
> > commit a1992f2f3b8e174d740a8f764d0d51344bed2eed
> > Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > 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 A?lusarz <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>

Thank you!

Any news on whether or not it solves the problem?

							Thanx, Paul

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>