From: Johannes Berg <johannes@sipsolutions.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>,
netdev@vger.kernel.org, linux-wireless@vger.kernel.org
Subject: Re: changing dev->needed_headroom/needed_tailroom?
Date: Mon, 05 Aug 2013 16:00:40 +0200 [thread overview]
Message-ID: <1375711240.8120.11.camel@jlt4.sipsolutions.net> (raw)
In-Reply-To: <1375449082.3927.5.camel@edumazet-glaptop> (sfid-20130802_151126_631897_9E569FA7)
On Fri, 2013-08-02 at 06:11 -0700, Eric Dumazet wrote:
> On Fri, 2013-08-02 at 10:55 +0200, Ben Hutchings wrote:
>
> > I don't think this is safe when the interface is running (even if
> > carrier is off). Some functions may read dev->needed_headroom twice and
> > rely on getting the same value each time.
>
> It should be no problem. Remaining unsafe places should be fixed.
Most interesting would be stack devs, which I hadn't even considered. In
any case, since I can't completely _rely_ on it, it's an optimisation,
the only bugs would be around the double-access and then running
over/under the SKB or so?
> We already had this discussion in the past, and some patches were
> issued. Check commit ae641949df01b85117845bec45328eab6d6fada1
> ("net: Remove all uses of LL_ALLOCATED_SPACE")
That would have addressed some of that, I guess.
I'm asking because some of the crypto stuff we do has fairly large
head/tailroom requirements and it seems I may need to add more. But if
you don't have crypto, it would be much smaller, so I figured we could
switch it.
johannes
next prev parent reply other threads:[~2013-08-05 14:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-26 14:50 changing dev->needed_headroom/needed_tailroom? Johannes Berg
2013-08-02 8:55 ` Ben Hutchings
2013-08-02 13:11 ` Eric Dumazet
2013-08-05 14:00 ` Johannes Berg [this message]
2013-08-20 10:00 ` Florian Fainelli
2013-08-20 16:20 ` Stephen Hemminger
2013-08-20 16:24 ` Johannes Berg
2013-08-20 16:29 ` Stephen Hemminger
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