From: Patrick McHardy <[EMAIL PROTECTED]> Date: Thu, 24 Jan 2008 07:47:39 +0100
> David Miller wrote: > > From: Patrick McHardy <[EMAIL PROTECTED]> > > Date: Thu, 24 Jan 2008 07:41:08 +0100 > > > >> David Miller wrote: > >> > >>> and nothing in that code path retakes the RTNL semaphore. > >>> > >> Actually we're always holding the rtnl during dumps, nlk->cb_mutex points > >> to rtnl_mutex in case of rtnetlink. It used to be held only during the > >> first > >> ->dump invocation and not on continuations, but I changed this a few > >> versions ago. > >> > > > > My bad. Thanks for the correction Patrick. > > > > But continuations can occur on subsequent recvmsg() calls, > > does it return to userspace with the mutex held? If so > > I'm pretty sure that's not allowed. > > No, the mutex is dropped between different ->dump invocations. Ok, great. This does mean, however, that the RTNL semaphore is dropped between ->dump() invocations on the same nlk->cb[] instance. And that has implications for the shortcut Stephen is taking. Stephen's patch assumes that during a (top-level) dump the table cannot change. And by the above, we can only conclude that it can in fact change between ->dump() calls for the same top-level dump run. So the removal of the -EBUSY code block in his patch isn't valid. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
