Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755743AbbLGQPd (ORCPT ); Mon, 7 Dec 2015 11:15:33 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58899 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932915AbbLGO5c (ORCPT ); Mon, 7 Dec 2015 09:57:32 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Duyck , Tom Lendacky , "David S. Miller" Subject: [PATCH 4.2 009/124] amd-xgbe: Fix race between access of desc and desc index Date: Mon, 7 Dec 2015 09:54:59 -0500 Message-Id: <20151207144920.129556614@linuxfoundation.org> X-Mailer: git-send-email 2.6.3 In-Reply-To: <20151207144919.656035367@linuxfoundation.org> References: <20151207144919.656035367@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2106 Lines: 58 4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Lendacky, Thomas" [ Upstream commit 20986ed826cbb36bb8f2d77f872e3c52d8d30647 ] During Tx cleanup it's still possible for the descriptor data to be read ahead of the descriptor index. A memory barrier is required between the read of the descriptor index and the start of the Tx cleanup loop. This allows a change to a lighter-weight barrier in the Tx transmit routine just before updating the current descriptor index. Since the memory barrier does result in extra overhead on arm64, keep the previous change to not chase the current descriptor value. This prevents the execution of the barrier for each loop performed. Suggested-by: Alexander Duyck Signed-off-by: Tom Lendacky Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/amd/xgbe/xgbe-dev.c | 2 +- drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) --- a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c +++ b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c @@ -1595,7 +1595,7 @@ static void xgbe_dev_xmit(struct xgbe_ch packet->rdesc_count, 1); /* Make sure ownership is written to the descriptor */ - wmb(); + smp_wmb(); ring->cur = cur_index + 1; if (!packet->skb->xmit_more || --- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c +++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c @@ -1816,6 +1816,10 @@ static int xgbe_tx_poll(struct xgbe_chan return 0; cur = ring->cur; + + /* Be sure we get ring->cur before accessing descriptor data */ + smp_rmb(); + txq = netdev_get_tx_queue(netdev, channel->queue_index); while ((processed < XGBE_TX_DESC_MAX_PROC) && -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/