linux-kernel - Re: Question on rhashtable in worst-case scenario.

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Date:	Thu, 31 Mar 2016 17:29:59 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Ben Greear <greearb@...delatech.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, tgraf@...g.ch
Subject: Re: Question on rhashtable in worst-case scenario.

On Thu, 2016-03-31 at 15:50 +0800, Herbert Xu wrote:
> On Thu, Mar 31, 2016 at 09:46:45AM +0200, Johannes Berg wrote:
> > 
> > 
> > In this case, I think perhaps you can just patch your local system
> > with
> > the many interfaces connecting to the same AP to add the parameter
> > Herbert suggested (.insecure_elasticity = true in sta_rht_params).
> > This
> > is, after all, very much a case that "normal" operation doesn't
> > even
> > get close to.
> I think you should just turn it on everywhere for mac80211.  Chain
> length checks simply don't make sense when you allow duplicate
> keys in the hash table.

Yes, that's a good point, and we can - in certain corner cases - end up
with duplicate keys even in normal operation.

Does removing this completely disable the "-EEXIST" error? I can't say
I fully understand the elasticity stuff in __rhashtable_insert_fast().

johannes