From 67a95e2022c7f0405408fb1f910283785ece354a Mon Sep 17 00:00:00 2001 From: Michael Chan Date: Wed, 4 May 2016 16:56:43 -0400 Subject: [PATCH] bnxt_en: Need memory barrier when processing the completion ring. 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 Signed-off-by: David S. Miller --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index 72eb29ed0359..f33ff205a0ea 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -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. */ -- 2.20.1