From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Josh Hunt <johunt@akamai.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"kaber@trash.net" <kaber@trash.net>,
Debabrata Banerjee <dbavatar@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"yoshfuji@linux-ipv6.org" <yoshfuji@linux-ipv6.org>,
"jmorris@namei.org" <jmorris@namei.org>,
"pekkas@netcore.fi" <pekkas@netcore.fi>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Bug in net/ipv6/ip6_fib.c:fib6_dump_table()
Date: Fri, 22 Jun 2012 01:50:56 +0400 [thread overview]
Message-ID: <20120621215056.GA24908@ms2.inr.ac.ru> (raw)
In-Reply-To: <1340310469.4604.6702.camel@edumazet-glaptop>
On Thu, Jun 21, 2012 at 10:27:49PM +0200, Eric Dumazet wrote:
> Looking at this code, it lacks proper synchronization
> between tree updaters and tree walkers.
>
> fib6_walker_lock rwlock is not enough to prevent races.
Hmm. As author of this weird code, I must say I honestly believed it was correct.
At least I tried. :-)
What's about 2bec5a336.., it does not look reasonable.
The idea was that when you change tree, you fixup sleeping walkers, moving
their location in tree to correct point. So, walkers must not have any stale pointers
at any times (except when you under table write lock) and no skips/counts are required.
I remember how damn difficult was it to make this right (well, sorry, if it is not yet :-)),
so that understand that if some update is forgotten or done incorrectly, it is not so easy to find,
but it is definitely worth of efforts.
Alexey
next prev parent reply other threads:[~2012-06-21 22:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-12 17:22 Debabrata Banerjee
2012-06-21 19:35 ` Josh Hunt
2012-06-21 20:27 ` Eric Dumazet
2012-06-21 21:50 ` Alexey Kuznetsov [this message]
2012-06-22 3:34 ` Gao feng
2012-06-22 6:49 ` Josh Hunt
2012-06-22 8:29 ` Eric Dumazet
2012-06-22 13:44 ` Josh Hunt
2012-06-22 18:13 ` Eric Dumazet
2012-06-22 21:12 ` Debabrata Banerjee
2012-06-23 0:02 ` David Miller
2012-06-23 5:37 ` Eric Dumazet
2012-06-23 20:55 ` Alexey Kuznetsov
2012-06-23 23:02 ` David Miller
2012-06-25 22:40 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120621215056.GA24908@ms2.inr.ac.ru \
--to=kuznet@ms2.inr.ac.ru \
--cc=davem@davemloft.net \
--cc=dbavatar@gmail.com \
--cc=eric.dumazet@gmail.com \
--cc=jmorris@namei.org \
--cc=johunt@akamai.com \
--cc=kaber@trash.net \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pekkas@netcore.fi \
--cc=yoshfuji@linux-ipv6.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®