Re: [PATCH] PKT_SCHED: Initialize list field in dummy qdiscs

[Patrick McHardy <kaber@xxxxxxxxx>]

Thomas Graf wrote:

> You mean before qdisc_lookup and until the reference is released
> again? These are huge locking regions involving calls which might
> sleep and possible qdisc_destroy calling paths.  So this won't
> work quite well.
Who cares about huge sections while holding reference counts ?
qdisc_destroy won't destroy the qdisc until all references have
been dropped, that's the whole point of it.

> So in my opinion we should screw that call_rcu because it doesn't
> make much sense. In case dev_activate is not synchronized with
> rtnl sempaphore we have to make sure that qdisc_destroy always
> locks on qdisc_tree_lock which is not the case for a few paths as
> of now, although I'm not sure if any of those actually ever call
> qdisc_destroy with refcnt==1.
>  
I'm also fixing up the remaining locking bugs, so before we start
reverting things lets just wait and see how it gets.

Regards
Patrick