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From:   NeilBrown <neilb@suse.com>
To:     Herbert Xu <herbert@gondor.apana.org.au>
Date:   Fri, 20 Jul 2018 16:24:16 +1000
Cc:     David Miller <davem@davemloft.net>, tgraf@suug.ch,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        eric.dumazet@gmail.com
Subject: Re: [PATCH - revised] rhashtable: detect when object movement might have invalidated a lookup
In-Reply-To: <20180717063020.rpqsgrbpwavklxz7@gondor.apana.org.au>
References: <20180601160613.7ud25g2ux55k3bma@gondor.apana.org.au> <87k1q8yh70.fsf@notabene.neil.brown.name> <20180711.224658.2077863065492745521.davem@davemloft.net> <20180711.224801.1129067473269289703.davem@davemloft.net> <87fu0kt5m0.fsf@notabene.neil.brown.name> <20180716005134.q4rfkfn3m5zzwt62@gondor.apana.org.au> <874lh0t1ls.fsf@notabene.neil.brown.name> <20180716021653.xtbyetdfc2uzxub3@gondor.apana.org.au> <871sc3uah9.fsf@notabene.neil.brown.name> <20180717063020.rpqsgrbpwavklxz7@gondor.apana.org.au>
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On Tue, Jul 17 2018, Herbert Xu wrote:

> On Mon, Jul 16, 2018 at 01:26:42PM +1000, NeilBrown wrote:
>>
>> Look in Documenation/RCU/rculist_nulls.txt.
>> The very first example is a typical lookup for a nulls list.
>> The above sample code would read:
>
> OK, but how will this work with rhlist? It would be very bad to
> have a feature that works for rhashtable but fails in strange
> ways when you use rhlist.

It should be easy enough to handle in rhlist too.
When inserting a new object, we put it at the start of the chain, and if
there was already a list with the same key, it gets moved to
the new object.
A walk could see some objects repeatedly when this happens, but that
is already possible.

Thanks,
NeilBrown


>
> Cheers,
> --=20
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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