From: Roland Dreier <[email protected]>
Date: Fri, 30 Jan 2009 09:35:52 -0800
> > > OK, thanks... what confused me is that several other drivers also do
> > > skb_linearize() in their hard_start_xmit method... eg bnx2x,
> > > via-velocity, mv643xx_eth. So there are several other lurking bugs to
> > > deal with here I guess.
> >
> > I don't know about the rest but bnx2x is certainly OK since it
> > only does so with IRQ enabled. It is legal to call skb_linearize
> > as long as you're sure that IRQs are enabled, which is always the
> > case for hard_start_xmit upon entry.
>
> I don't believe this is accurate. Calling skb_linearize() (on a kernel
> with CONFIG_HIGHMEM set) can end up calling local_bh_enable() in
> kunmap_skb_frag(), which can obviously cause problems if the initial
> context relies on having BHs disabled (as hard_start_xmit does).
local_bh_{enable,disable}() nests, so this is not a problem
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