From patchwork Fri Mar 11 15:28:53 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 8566491 Return-Path: X-Original-To: patchwork-linux-scsi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 76272C0553 for ; Fri, 11 Mar 2016 15:29:36 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 95A5620272 for ; Fri, 11 Mar 2016 15:29:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 982FC2026F for ; Fri, 11 Mar 2016 15:29:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932581AbcCKP3a (ORCPT ); Fri, 11 Mar 2016 10:29:30 -0500 Received: from www.linutronix.de ([62.245.132.108]:37929 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932424AbcCKP30 (ORCPT ); Fri, 11 Mar 2016 10:29:26 -0500 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1aeP0C-0006Yk-Em; Fri, 11 Mar 2016 16:29:20 +0100 From: Sebastian Andrzej Siewior To: linux-scsi@vger.kernel.org Cc: "James E.J. Bottomley" , "Martin K. Petersen" , rt@linutronix.de, Sebastian Andrzej Siewior , Vasu Dev , Christoph Hellwig , fcoe-devel@open-fcoe.org Subject: [PATCH 01/11] scsi/fcoe: lock online CPUs in fcoe_percpu_clean() Date: Fri, 11 Mar 2016 16:28:53 +0100 Message-Id: <1457710143-29182-2-git-send-email-bigeasy@linutronix.de> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1457710143-29182-1-git-send-email-bigeasy@linutronix.de> References: <1457710143-29182-1-git-send-email-bigeasy@linutronix.de> X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1, SHORTCIRCUIT=-0.0001, URIBL_BLOCKED=0.001 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP for_each_possible_cpu() with a cpu_online() + `thread' check possibly does the job. But there is a tiny race: Say CPU5 is reported online but is going down. And after fcoe_percpu_clean() saw that CPU5 is online it decided to enqueue a packet. After dev_alloc_skb() returned a skb that CPU is offline (or say the notifier destroyed the kthread). So we would OOps because `thread' is NULL. An alternative would be to lock the CPUs during our loop (so no CPU is going away) and then we iterate over the online mask. Cc: Vasu Dev Cc: "James E.J. Bottomley" Cc: "Martin K. Petersen" Cc: Christoph Hellwig Cc: fcoe-devel@open-fcoe.org Cc: linux-scsi@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior --- drivers/scsi/fcoe/fcoe.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c index 0efe7112fc1f..2b0d207f4b2b 100644 --- a/drivers/scsi/fcoe/fcoe.c +++ b/drivers/scsi/fcoe/fcoe.c @@ -2461,12 +2461,10 @@ static void fcoe_percpu_clean(struct fc_lport *lport) struct sk_buff *skb; unsigned int cpu; - for_each_possible_cpu(cpu) { + get_online_cpus(); + for_each_online_cpu(cpu) { pp = &per_cpu(fcoe_percpu, cpu); - if (!pp->thread || !cpu_online(cpu)) - continue; - skb = dev_alloc_skb(0); if (!skb) continue; @@ -2481,6 +2479,7 @@ static void fcoe_percpu_clean(struct fc_lport *lport) wait_for_completion(&fcoe_flush_completion); } + put_online_cpus(); } /**