From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966165AbcBDVMX (ORCPT ); Thu, 4 Feb 2016 16:12:23 -0500 Received: from down.free-electrons.com ([37.187.137.238]:41930 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965245AbcBDVKM (ORCPT ); Thu, 4 Feb 2016 16:10:12 -0500 From: Gregory CLEMENT To: "David S. Miller" , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Thomas Petazzoni Cc: Jason Cooper , Andrew Lunn , Sebastian Hesselbarth , Gregory CLEMENT , linux-arm-kernel@lists.infradead.org, Lior Amsalem , Nadav Haklai , Marcin Wojtas , Russell King - ARM Linux , Willy Tarreau , stable@vger.kernel.org Subject: [PATCH v3 net 2/7] net: mvneta: Fix the CPU choice in mvneta_percpu_elect Date: Thu, 4 Feb 2016 22:09:24 +0100 Message-Id: <1454620169-8156-3-git-send-email-gregory.clement@free-electrons.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1454620169-8156-1-git-send-email-gregory.clement@free-electrons.com> References: <1454620169-8156-1-git-send-email-gregory.clement@free-electrons.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When passing to the management of multiple RX queue, the mvneta_percpu_elect function was broken. The use of the modulo can lead to elect the wrong cpu. For example with rxq_def=2, if the CPU 2 goes offline and then online, we ended with the third RX queue activated in the same time on CPU 0 and CPU2, which lead to a kernel crash. With this fix, we don't try to get "the closer" CPU if the default CPU is gone, now we just use CPU 0 which always be there. Thanks to this, the code becomes more readable, easier to maintain and more predicable. Cc: stable@vger.kernel.org Fixes: 2dcf75e2793c ("net: mvneta: Associate RX queues with each CPU") Signed-off-by: Gregory CLEMENT --- drivers/net/ethernet/marvell/mvneta.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 90ff5c7e19ea..4c2d12423750 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -2849,9 +2849,14 @@ static void mvneta_percpu_disable(void *arg) static void mvneta_percpu_elect(struct mvneta_port *pp) { - int online_cpu_idx, max_cpu, cpu, i = 0; + int elected_cpu = 0, max_cpu, cpu, i = 0; + + /* Use the cpu associated to the rxq when it is online, in all + * the other cases, use the cpu 0 which can't be offline. + */ + if (cpu_online(pp->rxq_def)) + elected_cpu = pp->rxq_def; - online_cpu_idx = pp->rxq_def % num_online_cpus(); max_cpu = num_present_cpus(); for_each_online_cpu(cpu) { @@ -2862,7 +2867,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp) if ((rxq % max_cpu) == cpu) rxq_map |= MVNETA_CPU_RXQ_ACCESS(rxq); - if (i == online_cpu_idx) + if (cpu == elected_cpu) /* Map the default receive queue queue to the * elected CPU */ @@ -2873,7 +2878,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp) * the CPU bound to the default RX queue */ if (txq_number == 1) - txq_map = (i == online_cpu_idx) ? + txq_map = (cpu == elected_cpu) ? MVNETA_CPU_TXQ_ACCESS(1) : 0; else txq_map = mvreg_read(pp, MVNETA_CPU_MAP(cpu)) & -- 2.5.0