From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id W/GdBItGGVtTOAAAmS7hNA ; Thu, 07 Jun 2018 14:52:17 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id F3CFD608B8; Thu, 7 Jun 2018 14:52:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id BC970601C3; Thu, 7 Jun 2018 14:52:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org BC970601C3 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935154AbeFGOwO (ORCPT + 25 others); Thu, 7 Jun 2018 10:52:14 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:40902 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932674AbeFGOwL (ORCPT ); Thu, 7 Jun 2018 10:52:11 -0400 Received: from [148.252.241.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1fQvbP-0005Zm-Es; Thu, 07 Jun 2018 15:09:23 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1fQvbD-0003GJ-89; Thu, 07 Jun 2018 15:09:11 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Florian Fainelli" Date: Thu, 07 Jun 2018 15:05:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 367/410] net: systemport: Rewrite __bcm_sysport_tx_reclaim() In-Reply-To: X-SA-Exim-Connect-IP: 148.252.241.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.57-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Florian Fainelli commit 484d802d0f2f29c335563fcac2a8facf174a1bbc upstream. There is no need for complex checking between the last consumed index and current consumed index, a simple subtraction will do. This also eliminates the possibility of a permanent transmit queue stall under the following conditions: - one CPU bursts ring->size worth of traffic (up to 256 buffers), to the point where we run out of free descriptors, so we stop the transmit queue at the end of bcm_sysport_xmit() - because of our locking, we have the transmit process disable interrupts which means we can be blocking the TX reclamation process - when TX reclamation finally runs, we will be computing the difference between ring->c_index (last consumed index by SW) and what the HW reports through its register - this register is masked with (ring->size - 1) = 0xff, which will lead to stripping the upper bits of the index (register is 16-bits wide) - we will be computing last_tx_cn as 0, which means there is no work to be done, and we never wake-up the transmit queue, leaving it permanently disabled A practical example is e.g: ring->c_index aka last_c_index = 12, we pushed 256 entries, HW consumer index = 268, we mask it with 0xff = 12, so last_tx_cn == 0, nothing happens. Fixes: 80105befdb4b ("net: systemport: add Broadcom SYSTEMPORT Ethernet MAC driver") Signed-off-by: Florian Fainelli Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/net/ethernet/broadcom/bcmsysport.c | 33 ++++++++++------------ drivers/net/ethernet/broadcom/bcmsysport.h | 2 +- 2 files changed, 16 insertions(+), 19 deletions(-) --- a/drivers/net/ethernet/broadcom/bcmsysport.c +++ b/drivers/net/ethernet/broadcom/bcmsysport.c @@ -584,37 +584,33 @@ static unsigned int __bcm_sysport_tx_rec struct bcm_sysport_tx_ring *ring) { struct net_device *ndev = priv->netdev; - unsigned int c_index, last_c_index, last_tx_cn, num_tx_cbs; unsigned int pkts_compl = 0, bytes_compl = 0; + unsigned int txbds_processed = 0; struct bcm_sysport_cb *cb; + unsigned int txbds_ready; + unsigned int c_index; u32 hw_ind; /* Compute how many descriptors have been processed since last call */ hw_ind = tdma_readl(priv, TDMA_DESC_RING_PROD_CONS_INDEX(ring->index)); c_index = (hw_ind >> RING_CONS_INDEX_SHIFT) & RING_CONS_INDEX_MASK; - ring->p_index = (hw_ind & RING_PROD_INDEX_MASK); - - last_c_index = ring->c_index; - num_tx_cbs = ring->size; - - c_index &= (num_tx_cbs - 1); - - if (c_index >= last_c_index) - last_tx_cn = c_index - last_c_index; - else - last_tx_cn = num_tx_cbs - last_c_index + c_index; + txbds_ready = (c_index - ring->c_index) & RING_CONS_INDEX_MASK; netif_dbg(priv, tx_done, ndev, - "ring=%d c_index=%d last_tx_cn=%d last_c_index=%d\n", - ring->index, c_index, last_tx_cn, last_c_index); + "ring=%d old_c_index=%u c_index=%u txbds_ready=%u\n", + ring->index, ring->c_index, c_index, txbds_ready); - while (last_tx_cn-- > 0) { - cb = ring->cbs + last_c_index; + while (txbds_processed < txbds_ready) { + cb = &ring->cbs[ring->clean_index]; bcm_sysport_tx_reclaim_one(priv, cb, &bytes_compl, &pkts_compl); ring->desc_count++; - last_c_index++; - last_c_index &= (num_tx_cbs - 1); + txbds_processed++; + + if (likely(ring->clean_index < ring->size - 1)) + ring->clean_index++; + else + ring->clean_index = 0; } ring->c_index = c_index; @@ -1036,6 +1032,7 @@ static int bcm_sysport_init_tx_ring(stru netif_napi_add(priv->netdev, &ring->napi, bcm_sysport_tx_poll, 64); ring->index = index; ring->size = size; + ring->clean_index = 0; ring->alloc_size = ring->size; ring->desc_cpu = p; ring->desc_count = ring->size; --- a/drivers/net/ethernet/broadcom/bcmsysport.h +++ b/drivers/net/ethernet/broadcom/bcmsysport.h @@ -624,7 +624,7 @@ struct bcm_sysport_tx_ring { unsigned int desc_count; /* Number of descriptors */ unsigned int curr_desc; /* Current descriptor */ unsigned int c_index; /* Last consumer index */ - unsigned int p_index; /* Current producer index */ + unsigned int clean_index; /* Current clean index */ struct bcm_sysport_cb *cbs; /* Transmit control blocks */ struct dma_desc *desc_cpu; /* CPU view of the descriptor */ struct bcm_sysport_priv *priv; /* private context backpointer */