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

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Message-ID: <56F9941A.3080501@candelatech.com>
Date:	Mon, 28 Mar 2016 13:29:14 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Subject: Question on rhashtable in worst-case scenario.

Hello!

I have a use case for mac80211 where I create multiple stations to
the same remote peer MAC address.

I'm seeing cases where the rhashtable logic is returning -16 (EBUSY)
on insert (see sta_info_hash_add).
This is with the 4.4.6+ (plus local patches) kernel, and it has the patch mentioned
here:

https://lkml.org/lkml/2015/12/3/307

If I understand the code properly, my use case is going to be worst-case scenario,
where all of my items in the hash have the same key (peer mac addr).

I have my own secondary hash to handle most of my hot-path lookups, but I still need
the main hash to at least function in a linear-search manner.

Any idea what I can do to get rid of the EBUSY return code problem, or how
to debug it further?

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com