netdev - Re: [PATCH RFC] IPv6: Avoid taking write lock for /proc/net/ipv6

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]

Date:	Fri, 30 Dec 2011 17:09:05 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	joshhunt00@...il.com
Cc:	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] IPv6: Avoid taking write lock for
 /proc/net/ipv6_route

From: Josh Hunt <joshhunt00@...il.com>
Date: Wed, 28 Dec 2011 17:23:07 -0600

> lock_stat shows taking the write lock is causing the slowdown. Using
> this info I decided to write a version of fib6_clean_all() which
> replaces write_lock_bh(&table->tb6_lock) with
> read_lock_bh(&table->tb6_lock). With this new function I see the same
> results as with my rtnetlink iperf test. I guess my question is what
> am I missing? Is there a reason you need to take the write lock when
> reading the route table to display to proc?

You're not missing anything, it's just an oversight or laziness. :-)

I've applied your patch thanks.

Longer term we should make the ipv6 tree traversals RCU safe just
like net/ipv4/fib_trie.c is.  Then we can do away with even the
read locks for read-only traversals.

--
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