On Wed, Aug 31, 2011 at 11:05 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> You might want to remove also the first wmb() in qh_append_tds().
I think the first wmb() is used to order the two writing:
qtd->hw_token = HALT_BIT(ehci);
wmb ()
*dummy = *qtd;
Since dummy has been in hw queue already and must see halt bit of hw_token
first, the barrier should be kept, otherwise the transaction represented by qtd
may be executed too early and qtd->hw_next is still not ready.
thanks,
--
Ming Lei
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