Re: [PATCH net v2] openvswitch: fix a possible deadlock and lockdep warning

[Flavio Leitner <fbl-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Thu, Mar 27, 2014 at 10:19:23AM -0700, Pravin Shelar wrote:
> On Thu, Mar 27, 2014 at 7:05 AM, Flavio Leitner <fbl-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > There are two problematic situations.
> >
> > A deadlock can happen when is_percpu is false because it can get
> > interrupted while holding the spinlock. Then it executes
> > ovs_flow_stats_update() in softirq context which tries to get
> > the same lock.
> >
> > The second sitation is that when is_percpu is true, the code
> > correctly disables BH but only for the local CPU, so the
> > following can happen when locking the remote CPU without
> > disabling BH:
> >
> >        CPU#0                            CPU#1
> >   ovs_flow_stats_get()
> >    stats_read()
> >  +->spin_lock remote CPU#1        ovs_flow_stats_get()
> >  |  <interrupted>                  stats_read()
> >  |  ...                       +-->  spin_lock remote CPU#0
> >  |                            |     <interrupted>
> >  |  ovs_flow_stats_update()   |     ...
> >  |   spin_lock local CPU#0 <--+     ovs_flow_stats_update()
> >  +---------------------------------- spin_lock local CPU#1
> >
> > This patch disables BH for both cases fixing the deadlocks.
> 
> This bug is already fixed in OVS.

Could you point me to the commit? I am not finding anything
recent.