On Sun, 2015-10-18 at 22:21 -0700, Stephen Hemminger wrote:
> On Sat, 17 Oct 2015 00:21:44 -0400
> Michael Chan <mc...@broadcom.com> wrote:
>
> > +static inline u32 bnxt_tx_avail(struct bnxt *bp, struct bnxt_tx_ring_info
> > *txr)
> > +{
> > + /* Tell compiler to fetch tx indices from memory. */
> > + barrier();
>
> Actually, you are telling compiler not to reorder. Which may not
> be sufficient on some platforms.
Only a compiler barrier is needed here to prevent the compiler from
optimizing out the memory access of tx_prod and tx_cons, in case it
thinks that it has those values in some registers.
>
>
> > + return bp->tx_ring_size -
> > + ((txr->tx_prod - txr->tx_cons) & bp->tx_ring_mask);
> > +}
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