Re: [PATCH 2.6.20-rc3]: 8139cp: Don't blindly enable interrupts

[Jeff Garzik <jgarzik@pobox.com>]

Chris Lalancette wrote:
> Francois Romieu wrote:
>
> > Chris Lalancette <clalance@redhat.com> :
> > [...]
> >  
> >
> > >     Thanks for the comments.  While the patch you sent will help, there are
> > > still other places that will have problems.  For example, in netpoll_send_skb,
> > > we call local_irq_save(flags), then call dev->hard_start_xmit(), and then call
> > > local_irq_restore(flags).  This is a similar situation to what I described
> > > above; we will re-enable interrupts in cp_start_xmit(), when netpoll_send_skb
> > > doesn't expect that, and will probably run into issues.
> > >     Is there a problem with changing cp_start_xmit to use the
> > > spin_lock_irqsave(), besides the extra instructions it needs?
> > >    
> > No. Given the history of locking in netpoll and the content of
> > Documentation/networking/netdevices.txt, asking Herbert which rule(s)
> > the code is supposed to follow seemed safer to me.
> >
> > You can forget my patch.
> >
> > Please resend your patch inlined to Jeff as described in
> > http://linux.yyz.us/patch-format.html.
> >
> >  
> Francois,
>      Great.  Resending mail, shortening subject to < 65 characters and
> inlining the patch.
>
> Thanks,
> Chris Lalancette
>
> Similar to this commit:
>
> http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e
>
> It's not safe in cp_start_xmit to blindly call spin_lock_irq and then
> spin_unlock_irq, since it may very well be the case that cp_start_xmit
> was called with interrupts already disabled (I came across this bug in
> the context of netdump in RedHat kernels, but the same issue holds, for
> example, in netconsole). Therefore, replace all instances of
> spin_lock_irq and spin_unlock_irq with spin_lock_irqsave and
> spin_unlock_irqrestore, respectively, in cp_start_xmit(). I tested this
> against a fully-virtualized Xen guest using netdump, which happens to
> use the 8139cp driver to talk to the emulated hardware. I don't have a
> real piece of 8139cp hardware to test on, so someone else will have to
> do that.
>
> Signed-off-by: Chris Lalancette <clalance@redhat.com>

applied.

In the future, please remove the quoted emails stuff, and anything else 
that does not belong in the kernel changelog.  It must be hand-edited 
out, before using git-am to merge your patch into the kernel tree.

	Jeff



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