[Open-FCoE] [PATCH V2 11/13] fcoe: add mutex to protect create and destroy

Chris Leech christopher.leech at intel.com
Wed Jul 8 21:48:55 UTC 2009

On Wed, Jul 08, 2009 at 02:24:16PM -0700, Joe Eykholt wrote:
> Robert Love wrote:
> > On Wed, 2009-07-08 at 10:40 -0700, Chris Leech wrote:
> >> Rather than rely on the hostlist_lock to be held while creating exchange
> >> managers, serialize fcoe instance creation and destruction with a mutex.
> >> This will allow the hostlist addition to be moved out of fcoe_if_create(),
> >> which will simplify NPIV support.
> >>
> > Is there a reason that we don't use the rtnl_lock for protection? It's
> > already held when we get the NETDEV_UNREGISTER event (added in patch
> > 13/13). I believe that doing so would remove the need to defer the
> > fcoe_destroy() call since the deferral is only needed so that we don't
> > grab the rtnl_lock twice.
> I considered that, too.  It seems a bit like a layering violation to use
> it to protect create/delete/exit, but maybe it's OK to do since we
> need to grab rtnl_lock anyway.
> In fcoe_exit() we would have to be careful because
> unregister_netdevice_notifier() does rtnl_lock(),
> but if we did the unregister before grabbing rtnl_lock,
> that would be OK.
> It could completely eliminate the need for hostlist_lock and create_lock,
> so it seems like a nice idea.

I thought there was somewhere outside of create/destroy that the
host-list was being read, but it might just have been the module exit
case.  Removing the lock and only having one mutex for all this would be

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