From: "Michael Chan" <[EMAIL PROTECTED]>
Date: Thu, 11 Oct 2007 20:17:16 -0700
> On Thu, 2007-10-11 at 18:14 -0700, David Miller wrote:
> > + while (1) {
> > + work_done = tg3_poll_work(tp, work_done, budget);
> > +
> > + if (unlikely(tp->tg3_flags & TG3_FLAG_TX_RECOVERY_PENDING))
> > + goto tx_recovery;
> > +
> > + if (unlikely(work_done >= budget))
> > + break;
> > +
> > + if (likely(!tg3_has_work(tp))) {
> > + struct tg3_hw_status *sblk = tp->hw_status;
> > +
>
> --> new status block DMA
>
> > + if (tp->tg3_flags & TG3_FLAG_TAGGED_STATUS) {
> > + tp->last_tag = sblk->status_tag;
> > + rmb();
> > + } else
> > + sblk->status &= ~SD_STATUS_UPDATED;
>
> We need to read the sblk->status_tag before calling tg3_has_work(). If
> a new status block DMA happens in between (shown above), tp->last_tag
> will get the new tag and we will end up acknowledging work that we
> haven't processed.
Hmmm, the old code didn't do that and seemingly has the same
problem. Also, if you look at the before-patch code and think
about what it does if we ->poll() multiple times for a single
interrupt the side-effects are essentially the same.
What's the crucial difference?
> I'll go over this some more tonight and will send a patch to refine it.
Thanks Michael.
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