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GET /api/patches/770011/?format=api
{ "id": 770011, "url": "http://patchwork.ozlabs.org/api/patches/770011/?format=api", "web_url": "http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20170601224051.6106-12-jacob.e.keller@intel.com/", "project": { "id": 46, "url": "http://patchwork.ozlabs.org/api/projects/46/?format=api", "name": "Intel Wired Ethernet development", "link_name": "intel-wired-lan", "list_id": "intel-wired-lan.osuosl.org", "list_email": "intel-wired-lan@osuosl.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20170601224051.6106-12-jacob.e.keller@intel.com>", "list_archive_url": null, "date": "2017-06-01T22:40:47", "name": "[11/15] fm10k: prevent race condition of __FM10K_SERVICE_SCHED", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": false, "hash": "4b86eaf0e1e381fc6d406ed1a2c1ab8e8db61a38", "submitter": { "id": 9784, "url": "http://patchwork.ozlabs.org/api/people/9784/?format=api", "name": "Jacob Keller", "email": "jacob.e.keller@intel.com" }, "delegate": { "id": 68, "url": "http://patchwork.ozlabs.org/api/users/68/?format=api", "username": "jtkirshe", "first_name": "Jeff", "last_name": "Kirsher", "email": "jeffrey.t.kirsher@intel.com" }, "mbox": "http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20170601224051.6106-12-jacob.e.keller@intel.com/mbox/", "series": [], "comments": "http://patchwork.ozlabs.org/api/patches/770011/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/770011/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<intel-wired-lan-bounces@osuosl.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "intel-wired-lan@lists.osuosl.org" ], "Delivered-To": [ "patchwork-incoming@bilbo.ozlabs.org", "intel-wired-lan@lists.osuosl.org" ], "Received": [ "from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136])\n\t(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))\n\t(No client certificate requested)\n\tby ozlabs.org (Postfix) with ESMTPS id 3wf2Pk58Sxz9sN8\n\tfor <incoming@patchwork.ozlabs.org>;\n\tFri, 2 Jun 2017 08:41:14 +1000 (AEST)", "from localhost (localhost [127.0.0.1])\n\tby silver.osuosl.org (Postfix) with ESMTP id 30AF630CA1;\n\tThu, 1 Jun 2017 22:41:13 +0000 (UTC)", "from silver.osuosl.org ([127.0.0.1])\n\tby localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024)\n\twith ESMTP id 9tVMq6tkoqvb; Thu, 1 Jun 2017 22:41:08 +0000 (UTC)", "from ash.osuosl.org (ash.osuosl.org [140.211.166.34])\n\tby silver.osuosl.org (Postfix) with ESMTP id 0943230C89;\n\tThu, 1 Jun 2017 22:41:02 +0000 (UTC)", "from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136])\n\tby ash.osuosl.org (Postfix) with ESMTP id 069521C3EC9\n\tfor <intel-wired-lan@lists.osuosl.org>;\n\tThu, 1 Jun 2017 22:40:58 +0000 (UTC)", "from localhost (localhost [127.0.0.1])\n\tby silver.osuosl.org (Postfix) with ESMTP id EF23A30C65\n\tfor <intel-wired-lan@lists.osuosl.org>;\n\tThu, 1 Jun 2017 22:40:57 +0000 (UTC)", "from silver.osuosl.org ([127.0.0.1])\n\tby localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024)\n\twith ESMTP id mz0c-CqnbmcK for <intel-wired-lan@lists.osuosl.org>;\n\tThu, 1 Jun 2017 22:40:57 +0000 (UTC)", "from mga14.intel.com (mga14.intel.com [192.55.52.115])\n\tby silver.osuosl.org (Postfix) with ESMTPS id E611330C63\n\tfor <intel-wired-lan@lists.osuosl.org>;\n\tThu, 1 Jun 2017 22:40:56 +0000 (UTC)", "from fmsmga001.fm.intel.com ([10.253.24.23])\n\tby fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384;\n\t01 Jun 2017 15:40:56 -0700", "from jekeller-desk.amr.corp.intel.com ([10.166.35.158])\n\tby fmsmga001.fm.intel.com with ESMTP; 01 Jun 2017 15:40:56 -0700" ], "X-Virus-Scanned": [ "amavisd-new at osuosl.org", "amavisd-new at osuosl.org" ], "X-Greylist": "domain auto-whitelisted by SQLgrey-1.7.6", "X-ExtLoop1": "1", "X-IronPort-AV": "E=Sophos; i=\"5.39,281,1493708400\"; d=\"scan'208\";\n\ta=\"1155582876\"", "From": "Jacob Keller <jacob.e.keller@intel.com>", "To": "Intel Wired LAN <intel-wired-lan@lists.osuosl.org>", "Date": "Thu, 1 Jun 2017 15:40:47 -0700", "Message-Id": "<20170601224051.6106-12-jacob.e.keller@intel.com>", "X-Mailer": "git-send-email 2.13.0.311.g0339965c70d6", "In-Reply-To": "<20170601224051.6106-1-jacob.e.keller@intel.com>", "References": "<20170601224051.6106-1-jacob.e.keller@intel.com>", "Subject": "[Intel-wired-lan] [PATCH 11/15] fm10k: prevent race condition of\n\t__FM10K_SERVICE_SCHED", "X-BeenThere": "intel-wired-lan@osuosl.org", "X-Mailman-Version": "2.1.18-1", "Precedence": "list", "List-Id": "Intel Wired Ethernet Linux Kernel Driver Development\n\t<intel-wired-lan.osuosl.org>", "List-Unsubscribe": "<https://lists.osuosl.org/mailman/options/intel-wired-lan>, \n\t<mailto:intel-wired-lan-request@osuosl.org?subject=unsubscribe>", "List-Archive": "<http://lists.osuosl.org/pipermail/intel-wired-lan/>", "List-Post": "<mailto:intel-wired-lan@osuosl.org>", "List-Help": "<mailto:intel-wired-lan-request@osuosl.org?subject=help>", "List-Subscribe": "<https://lists.osuosl.org/mailman/listinfo/intel-wired-lan>, \n\t<mailto:intel-wired-lan-request@osuosl.org?subject=subscribe>", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=\"us-ascii\"", "Content-Transfer-Encoding": "7bit", "Errors-To": "intel-wired-lan-bounces@osuosl.org", "Sender": "\"Intel-wired-lan\" <intel-wired-lan-bounces@osuosl.org>" }, "content": "Although very unlikely, it is possible that cancel_work_sync() may stop\nthe service_task before it actually started. In this case, the\n__FM10K_SERVICE_SCHED bit will never be cleared. This results in the\nservice task being unable to reschedule in the future. Add a helper\nfunction which sets the service disable bit, waits for the service task\nto stop and clears the schedule bit, thus avoiding the race condition.\nWe know the schedule bit is safe to clear because the cancel_work_sync()\nguarantees the service task is not running.\n\nAdd a helper function also to restart the service task, for symmetry.\nThis is not strictly needed but helps the mental model of how to stop\nand start the service task.\n\nThis race could only happen in fm10k_suspend/fm10k_resume as this is the\nonly place where the service task is actually restarted. Thus,\nsuspend/resume testing would be ideal. However, note that the chance of\nthis happening is very slim as the service event is scheduled for\nimmediate execution, and you would have to trigger a suspend at almost\nthe exact same time as the service task was scheduled.\n\nSigned-off-by: Jacob Keller <jacob.e.keller@intel.com>\n---\n drivers/net/ethernet/intel/fm10k/fm10k_pci.c | 32 ++++++++++++++++++++++------\n 1 file changed, 25 insertions(+), 7 deletions(-)", "diff": "diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c\nindex 2d94a16f9613..206da6b7c46a 100644\n--- a/drivers/net/ethernet/intel/fm10k/fm10k_pci.c\n+++ b/drivers/net/ethernet/intel/fm10k/fm10k_pci.c\n@@ -118,6 +118,27 @@ static void fm10k_service_event_complete(struct fm10k_intfc *interface)\n \t\tfm10k_service_event_schedule(interface);\n }\n \n+static void fm10k_stop_service_event(struct fm10k_intfc *interface)\n+{\n+\tset_bit(__FM10K_SERVICE_DISABLE, interface->state);\n+\tcancel_work_sync(&interface->service_task);\n+\n+\t/* It's possible that cancel_work_sync stopped the service task from\n+\t * running before it could actually start. In this case the\n+\t * __FM10K_SERVICE_SCHED bit will never be cleared. Since we know that\n+\t * the service task cannot be running at this point, we need to clear\n+\t * the scheduled bit, as otherwise the service task may never be\n+\t * restarted.\n+\t */\n+\tclear_bit(__FM10K_SERVICE_SCHED, interface->state);\n+}\n+\n+static void fm10k_start_service_event(struct fm10k_intfc *interface)\n+{\n+\tclear_bit(__FM10K_SERVICE_DISABLE, interface->state);\n+\tfm10k_service_event_schedule(interface);\n+}\n+\n /**\n * fm10k_service_timer - Timer Call-back\n * @data: pointer to interface cast into an unsigned long\n@@ -2131,8 +2152,7 @@ static void fm10k_remove(struct pci_dev *pdev)\n \n \tdel_timer_sync(&interface->service_timer);\n \n-\tset_bit(__FM10K_SERVICE_DISABLE, interface->state);\n-\tcancel_work_sync(&interface->service_task);\n+\tfm10k_stop_service_event(interface);\n \n \t/* free netdev, this may bounce the interrupts due to setup_tc */\n \tif (netdev->reg_state == NETREG_REGISTERED)\n@@ -2170,8 +2190,7 @@ static void fm10k_prepare_suspend(struct fm10k_intfc *interface)\n \t * stopped. We stop the watchdog task until after we resume software\n \t * activity.\n \t */\n-\tset_bit(__FM10K_SERVICE_DISABLE, interface->state);\n-\tcancel_work_sync(&interface->service_task);\n+\tfm10k_stop_service_event(interface);\n \n \tfm10k_prepare_for_reset(interface);\n }\n@@ -2198,9 +2217,8 @@ static int fm10k_handle_resume(struct fm10k_intfc *interface)\n \tinterface->link_down_event = jiffies + (HZ);\n \tset_bit(__FM10K_LINK_DOWN, interface->state);\n \n-\t/* clear the service task disable bit to allow service task to start */\n-\tclear_bit(__FM10K_SERVICE_DISABLE, interface->state);\n-\tfm10k_service_event_schedule(interface);\n+\t/* restart the service task */\n+\tfm10k_start_service_event(interface);\n \n \treturn err;\n }\n", "prefixes": [ "11/15" ] }