From: Eric Dumazet <eric.dumazet@gmail.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Elmar Vonlanthen" <evonlanthen@gmail.com>,
linux-kernel@vger.kernel.org, netdev <netdev@vger.kernel.org>,
"Timo Teräs" <timo.teras@iki.fi>
Subject: Re: PROBLEM: System call 'sendmsg' of process ospfd (quagga) causes kernel oops
Date: Tue, 18 Oct 2011 12:01:33 +0200 [thread overview]
Message-ID: <1318932093.2657.26.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> (raw)
In-Reply-To: <20111018093411.GA15165@gondor.apana.org.au>
Le mardi 18 octobre 2011 à 11:34 +0200, Herbert Xu a écrit :
> On Tue, Oct 18, 2011 at 04:30:32AM +0200, Eric Dumazet wrote:
> >
> > If David/Herbert/Timo agree, then patch should find its way into current
> > kernel, then to stable trees as well.
>
> Actually, I think we should instead fix the users of needed_headroom
> to not read it twice which is causing problems here.
>
> GRE tunnels by their nature do not have a fixed value for
> needed_headroom. As the underlying routes change the necessary
> headroom may need to be adjusted due to further encapsulation such
> as IPsec.
>
> Keeping it constant from tunnel creation may result in suboptimal
> performance due to unnecessary header reallocations.
>
> However, until we audit the stack to see if there are further
> instances of double-readings such as the one causing the crash
> here, I'm fine with your patch making it constant.
>
> Once we're sure that all of the double-readings are gone we
> can revert to a dynamic needed_headroom.
>
Sure, we can work on this path for future kernels.
Adding an RCU protected structure to hold hard_header_len /
needed_headroom / needed_tailroom should be possible, but this adds yet
another pointer dereference...
Thanks !
next prev parent reply other threads:[~2011-10-18 10:01 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CA+0Zf5Be5JUSvssH9CrDQq=jtETZr=veAPC7jriM8B-FZKbbpg@mail.gmail.com>
2011-10-14 14:57 ` PROBLEM: System call 'sendmsg' of process ospfd (quagga) causes kernel oops Eric Dumazet
2011-10-17 7:16 ` Elmar Vonlanthen
2011-10-18 2:30 ` Eric Dumazet
2011-10-18 9:34 ` Herbert Xu
2011-10-18 10:01 ` Eric Dumazet [this message]
2011-10-18 10:05 ` Herbert Xu
2011-10-18 10:23 ` Eric Dumazet
2011-10-18 10:45 ` Herbert Xu
2011-10-18 11:37 ` Eric Dumazet
2011-10-18 11:49 ` Herbert Xu
2011-10-18 12:56 ` Eric Dumazet
2011-10-18 13:45 ` Herbert Xu
2011-10-19 7:09 ` David Miller
2011-10-19 7:18 ` Eric Dumazet
2011-10-19 7:30 ` David Miller
2011-10-19 7:52 ` Eric Dumazet
2011-10-19 8:02 ` David Miller
2011-10-19 8:08 ` Herbert Xu
2011-10-20 9:30 ` David Miller
2011-10-20 9:35 ` Herbert Xu
2011-10-20 20:21 ` David Miller
2011-10-25 11:54 ` Herbert Xu
2011-10-26 3:12 ` David Miller
2011-11-18 12:18 ` [0/6] Replace LL_ALLOCATED_SPACE to allow needed_headroom adjustment Herbert Xu
2011-11-18 12:20 ` [PATCH 3/6] net: Remove all uses of LL_ALLOCATED_SPACE Herbert Xu
2011-11-18 12:20 ` [PATCH 1/6] ipv4: " Herbert Xu
2011-11-18 12:20 ` [PATCH 2/6] ipv6: " Herbert Xu
2011-11-18 12:20 ` [PATCH 4/6] net: Remove LL_ALLOCATED_SPACE Herbert Xu
2011-11-18 12:20 ` [PATCH 5/6] packet: Add needed_tailroom to packet_sendmsg_spkt Herbert Xu
2011-11-18 12:20 ` [PATCH 6/6] ip_gre: Set needed_headroom dynamically again Herbert Xu
2011-11-18 20:01 ` [0/6] Replace LL_ALLOCATED_SPACE to allow needed_headroom adjustment David Miller
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