Hi Cong, On Sat, Nov 12, 2016, at 01:55, Cong Wang wrote: > On Fri, Nov 11, 2016 at 4:23 PM, Paul E. McKenney > <paul...@linux.vnet.ibm.com> wrote: > > > > Ah! This net_mutex is different than RTNL. Should synchronize_net() be > > modified to check for net_mutex being held in addition to the current > > checks for RTNL being held? > > > > Good point! > > Like commit be3fc413da9eb17cce0991f214ab0, checking > for net_mutex for this case seems to be an optimization, I assume > synchronize_rcu_expedited() and synchronize_rcu() have the same > behavior... > > diff --git a/net/core/dev.c b/net/core/dev.c > index eaad4c2..3415b6b 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -7762,7 +7762,7 @@ EXPORT_SYMBOL(free_netdev); > void synchronize_net(void) > { > might_sleep(); > - if (rtnl_is_locked()) > + if (rtnl_is_locked() || lockdep_is_held(&net_mutex)) > synchronize_rcu_expedited();
I don't think we should depend on lockdep for this check but rather use mutex_is_locked here (I think it would fail to build like this without CONFIG_LOCKDEP). Bye, Hannes