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bnxt_en: Need memory barrier when processing the completion ring.

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The code determines if the next ring entry is valid before proceeding
further to read the rest of the entry.  The CPU can re-order and read
the rest of the entry first, possibly reading a stale entry, if DMA
of a new entry happens right after reading it.  This issue can be
readily seen on a ppc64 system, causing it to crash.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael Chan 2016-05-04 16:56:43 -04:00 committed by David S. Miller
parent 32b583a0cb
commit 67a95e2022
1 changed files with 4 additions and 0 deletions
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4
drivers/net/ethernet/broadcom/bnxt/bnxt.c
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@ -1388,6 +1388,10 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
if (!TX_CMP_VALID(txcmp, raw_cons))
break;
/* The valid test of the entry must be done first before
* reading any further.
*/
rmb();
if (TX_CMP_TYPE(txcmp) == CMP_TYPE_TX_L2_CMP) {
tx_pkts++;
/* return full budget so NAPI will complete. */