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bnx2: use READ_ONCE() instead of barrier()

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barrier() is a big hammer compared to READ_ONCE(),
and requires comments explaining what is protected.

READ_ONCE() is more precise and compiler should generate
better overall code.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-11-19 14:57:11 -08:00 committed by David S. Miller
parent d21dbdfe0a
commit b668534c1d
1 changed files with 5 additions and 12 deletions
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17
drivers/net/ethernet/broadcom/bnx2.c
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@ -254,13 +254,10 @@ static inline u32 bnx2_tx_avail(struct bnx2 *bp, struct bnx2_tx_ring_info *txr)
{
u32 diff;
/* Tell compiler to fetch tx_prod and tx_cons from memory. */
barrier();
/* The ring uses 256 indices for 255 entries, one of them
* needs to be skipped.
*/
diff = txr->tx_prod - txr->tx_cons;
diff = READ_ONCE(txr->tx_prod) - READ_ONCE(txr->tx_cons);
if (unlikely(diff >= BNX2_TX_DESC_CNT)) {
diff &= 0xffff;
if (diff == BNX2_TX_DESC_CNT)
@ -2839,10 +2836,8 @@ bnx2_get_hw_tx_cons(struct bnx2_napi *bnapi)
{
u16 cons;
/* Tell compiler that status block fields can change. */
barrier();
cons = *bnapi->hw_tx_cons_ptr;
barrier();
cons = READ_ONCE(*bnapi->hw_tx_cons_ptr);
if (unlikely((cons & BNX2_MAX_TX_DESC_CNT) == BNX2_MAX_TX_DESC_CNT))
cons++;
return cons;
@ -3141,10 +3136,8 @@ bnx2_get_hw_rx_cons(struct bnx2_napi *bnapi)
{
u16 cons;
/* Tell compiler that status block fields can change. */
barrier();
cons = *bnapi->hw_rx_cons_ptr;
barrier();
cons = READ_ONCE(*bnapi->hw_rx_cons_ptr);
if (unlikely((cons & BNX2_MAX_RX_DESC_CNT) == BNX2_MAX_RX_DESC_CNT))
cons++;
return cons;