Re: [B.A.T.M.A.N.] [PATCH v3 1/2] batman-adv: fix race conditions on interface removal

[Sven Eckelmann <sven@narfation.org>]

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On Samstag, 29. Oktober 2016 04:46:46 CEST Linus Lüssing wrote:
[...]
> > [...]
> > > +bool batadv_forw_packet_steal(struct batadv_forw_packet *forw_packet,
> > > +			      spinlock_t *lock)
> > > +{
> > > +	struct hlist_head head = HLIST_HEAD_INIT;
[...]
> > > +	/* Just to spot misuse of this function */
> > > +	hlist_add_head(&forw_packet->bm_list, &head);
> > > +	hlist_add_fake(&forw_packet->bm_list);
> > 
> > Sorry, I don't get how this should spot misuse via this extra hlist_add_head.
> > You first add the packet to the list (on the stack) and then setting pprev
> > pointer to itself. So you basically have a fake hashed node with next pointer
> > set to NULL. Wouldn't it be better here to use INIT_HLIST_NODE instead of
> > hlist_add_head? I would even say that INIT_HLIST_NODE isn't needed here
> > because you already did this during batadv_forw_packet_alloc.
> > 
> > But I would assume that you actually only wanted hlist_add_fake for the
> > WARN_ONCE in batadv_forw_packet_queue, right?
> 
> Right :). I'm only using the _fake() variant for this WARN_ONCE.
> (So I'll leave that as is? Or too confusing? Do you want me to
> reword / clarify something better in the code?)

I think the _fake stuff + comment is ok. But the add to the hlist_head
on the stack is confusing and maybe should be removed.

Kind regards,
	Sven

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