netdev - Re: [PATCH 2/3 net-next] rhashtable: Use spin_lock_bh

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150314022118.GB10086@gondor.apana.org.au>
Date:	Sat, 14 Mar 2015 13:21:18 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	tgraf@...g.ch, netdev@...r.kernel.org, daniel@...earbox.net
Subject: Re: [PATCH 2/3 net-next] rhashtable: Use spin_lock_bh_nested()
 consistently

On Fri, Mar 13, 2015 at 12:54:11PM -0400, David Miller wrote:
> From: Thomas Graf <tgraf@...g.ch>
> Date: Fri, 13 Mar 2015 15:45:20 +0100
> 
> > No change in behaviour as the outer lock already disables softirq
> > but it prevents bugs down the line as this lock logically requires
> > the BH variant.
> > 
> > Signed-off-by: Thomas Graf <tgraf@...g.ch>
> 
> I would prefer you don't do this.
> 
> x_bh() may be relatively cheap, but it is not zero cost.
> 
> If there is an invariant that when we are called here BH
> is disabled, make it explicit.

Agreed.  I dropped the _bh precisely for this reason when I did
the arbitrary rehash.  Please don't add it back because it serves
zero purpose.  Only the outside lock should do _bh while the
nested one should not.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html