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bna: CQ Read Fix

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Valid bit check for completion needs read fence, so that it does not get
reordered with other loads.

Signed-off-by: Rasesh Mody <rmody@brocade.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rasesh Mody 2013-12-17 17:07:37 -08:00 committed by David S. Miller
parent 66f9513a12
commit 17a30a14db
1 changed files with 22 additions and 1 deletions
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23
drivers/net/ethernet/brocade/bna/bnad.c
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@ -601,7 +601,18 @@ bnad_cq_process(struct bnad *bnad, struct bna_ccb *ccb, int budget)
cq = ccb->sw_q; cq = ccb->sw_q;
cmpl = &cq[ccb->producer_index]; cmpl = &cq[ccb->producer_index];
while (cmpl->valid && (packets < budget)) { while (packets < budget) {
if (!cmpl->valid)
break;
/* The 'valid' field is set by the adapter, only after writing
* the other fields of completion entry. Hence, do not load
* other fields of completion entry *before* the 'valid' is
* loaded. Adding the rmb() here prevents the compiler and/or
* CPU from reordering the reads which would potentially result
* in reading stale values in completion entry.
*/
rmb();
BNA_UPDATE_PKT_CNT(pkt_rt, ntohs(cmpl->length)); BNA_UPDATE_PKT_CNT(pkt_rt, ntohs(cmpl->length));
if (bna_is_small_rxq(cmpl->rxq_id)) if (bna_is_small_rxq(cmpl->rxq_id))
@ -641,6 +652,16 @@ bnad_cq_process(struct bnad *bnad, struct bna_ccb *ccb, int budget)
if (!next_cmpl->valid) if (!next_cmpl->valid)
break; break;
/* The 'valid' field is set by the adapter, only
* after writing the other fields of completion
* entry. Hence, do not load other fields of
* completion entry *before* the 'valid' is
* loaded. Adding the rmb() here prevents the
* compiler and/or CPU from reordering the reads
* which would potentially result in reading
* stale values in completion entry.
*/
rmb();
len = ntohs(next_cmpl->length); len = ntohs(next_cmpl->length);
flags = ntohl(next_cmpl->flags); flags = ntohl(next_cmpl->flags);