On Fri, Nov 11, 2016 at 4:55 PM, Cong Wang <xiyou.wangc...@gmail.com> 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...
Thinking a bit more, I think commit be3fc413da9eb17cce0991f gets wrong on rtnl_is_locked(), the lock could be locked by other process not by the current one, therefore it should be lockdep_rtnl_is_held() which, however, is defined only when LOCKDEP is enabled... Sigh. I don't see any better way than letting callers decide if they want the expedited version or not, but this requires changes of all callers of synchronize_net(). Hm.
