On Wed, 25 Jul 2007 01:31:54 -0700 (PDT)
David Miller <[EMAIL PROTECTED]> wrote:
>
> We're getting there, slowly...
>
> 1) netif_napi_init() is added, the workqueue/requeue stuff
> as discussed is not needed so you won't see that here
>
> 2) all cases where netif_rx_complete() are invoked in contexts
> where cpu interrupts are known to be disabled are replaced
> with __netif_rx_complete()
>
> Most drivers are in good shape, although some still have very
> questionable netif_rx_complete() handling, in that racy area that
> Rusty and myself were discussing today.
>
> My inclination is to wrap those sequences around with an IRQ
> safe spinlock to fix the race provably, and then if driver
> authors want to optimize that away with techniques like those
> that tg3, bnx2, sky2, skge et al. use, that's fine but can
> be done later.
>
> To some extent it's mechanical work if you know what to look
> for, so any relative patches for that stuff would be much
> appreciated and I'll integrate such patches rapidly and without
> delay.
>
> Besides that the only major issue is netpoll and I have some
> ideas on how to handle that, which I'll try to implement
> tonight and tomorrow.
>
> Another thing that's really apparent now is all the wacky
> napi->weight values various drivers use. Just grep for
> netif_napi_init() in the patch or a patched tree to see what
> I mean. So much of it doesn't make any sense and I'm tempted
> to just remove the argument and make everyone use 32 or 64
> or something like that :-) Or, default to some value across
> the board, and let drivers override that on a case by case
> basis with a BIG FAT COMMENT above the override describing
> why the different value is being used and precisely what
> tests were performed to validate that different value.
>
The usage of NAPI on 8139cp and 8139too seems dodgy;
these drivers expect this to work:
local_irq_save(flags);
cpw16_f(IntrMask, cp_intr_mask);
__netif_rx_complete(dev);
local_irq_restore(flags);
It works on SMP only because if poll races with IRQ,
the IRQ is not masked or cleared so the IRQ will get restarted.
Better would be to change it to:
spin_lock_irqsave(&cp->lock, flags);
cpw16_f(IntrMask, cp_intr_mask);
__netif_rx_complete(dev);
spin_unlock_irqrestore(&cp->lock, flags);
Which actually is same code on UP.
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