From patchwork Wed Feb 5 02:30:56 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rajat Jain X-Patchwork-Id: 3584231 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: patchwork-linux-pci@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 82DEA9F2E9 for ; Wed, 5 Feb 2014 02:32:01 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8D056201B4 for ; Wed, 5 Feb 2014 02:32:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 975CE20122 for ; Wed, 5 Feb 2014 02:31:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932280AbaBECbB (ORCPT ); Tue, 4 Feb 2014 21:31:01 -0500 Received: from mail-pa0-f54.google.com ([209.85.220.54]:57592 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932097AbaBECa7 (ORCPT ); Tue, 4 Feb 2014 21:30:59 -0500 Received: by mail-pa0-f54.google.com with SMTP id fa1so9383184pad.27 for ; Tue, 04 Feb 2014 18:30:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :content-type:content-transfer-encoding; bh=Z3R6iiFVEYmYrk09qz+oQJ4cbZW6I9K8eQ/aW9TM70c=; b=07eFc5VjqmV75QV1fBTLHX5kShqrK0vNSBwkP5zWV+MK/SoTOuhAaEJzE2rKAkZ4O/ BmwIukW1ELWiqqSLJlIq3NivqPWTJaeDAJx1CBW7BykG+NqaVlIdjBswYh52WTJ+Vgpc TUMWi5gR5yDIHMu/I8Q4GgZS6IvS4H1IumiXrz10cs6CKinMAptCDwcu5rKXIh3ItQSm zY2JqTsSIUhbf19Pu4iJfIcAC1bxOm+t10RH61oAD0MQIDHvF2wUqngv12ahDTApMW1U yjiIBXNELVDR9YJBIqhIHzIbF7zvGqj6ggSgeml/tI9TQzQfJP39hSaNet8sleddDMsN q4qQ== X-Received: by 10.68.242.68 with SMTP id wo4mr48448826pbc.32.1391567459358; Tue, 04 Feb 2014 18:30:59 -0800 (PST) Received: from [192.168.211.137] ([66.129.239.13]) by mx.google.com with ESMTPSA id lh13sm183852571pab.4.2014.02.04.18.30.57 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 04 Feb 2014 18:30:58 -0800 (PST) Message-ID: <52F1A260.8010609@gmail.com> Date: Tue, 04 Feb 2014 18:30:56 -0800 From: Rajat Jain User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Bjorn Helgaas , "Rafael J. Wysocki" , Kenji Kaneshige , Alex Williamson , Yijing Wang , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Yinghai Lu CC: Guenter Roeck , Rajat Jain , Rajat Jain Subject: [PATCH v4 7/8] pciehp: Ensure very fast hotplug events are also processed. Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, T_DKIM_INVALID, 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 Today, this is how all the hotplug and unplug events work: Hotplug / Removal needs to be done => Set slot->state (protected by slot->lock) to either POWERON_STATE (for enabling) or POWEROFF_STATE (for disabling). => Submit the work item for pciehp_power_thread() to slot->wq. Problem: There is a problem if the hotplug events can happen fast enough that they do not give SW enough time to add or remove the new devices. => Assume: Event for unplug comes (e.g. surprise removal). But before the pciehp_power_thread() work item was executed, the card was replaced by another card, causing surprise hotplug event. => What goes wrong: => The hot-removal event sets slot->state to POWEROFF_STATE, and schedules the pciehp_power_thread(). => The hot-add event sets slot->state to POWERON_STATE, and schedules the pciehp_power_thread(). => Now the pciehp_power_thread() is scheduled twice, and on both occasions it will find POWERON_STATE and will try to add the devices on the slot, and will fail complaining that the devices already exist. => Why this is a problem: If the device was replaced between the hot removal and hot-add, then we should unload the old driver and reload the new one. This does not happen today. The kernel or the driver is not even aware that the device was replaced. The problem is that the pciehp_power_thread() only looks at the slot->state which would only contain the *latest* state - not the actual event (add / remove) that was the intent of the IRQ handler who submitted the work. What this patch does: => Hotplug events pass on an actual request (for addition or removal) to pciehp_power_thread() which is local to that work item submission. => pciehp_power_thread() does not need to look at slote->state and hence no locks needed in that. => Essentially this results in all the hotplug and unplug events "replayed" by pciehp_power_thread(). Signed-off-by: Rajat Jain Signed-off-by: Rajat Jain Signed-off-by: Guenter Roeck --- drivers/pci/hotplug/pciehp_ctrl.c | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-) diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index b418e3b..3e40ec0 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -276,6 +276,9 @@ static int remove_board(struct slot *p_slot) struct power_work_info { struct slot *p_slot; struct work_struct work; + unsigned int req; +#define DISABLE_REQ 0 +#define ENABLE_REQ 1 }; /** @@ -291,10 +294,8 @@ static void pciehp_power_thread(struct work_struct *work) container_of(work, struct power_work_info, work); struct slot *p_slot = info->p_slot; - mutex_lock(&p_slot->lock); - switch (p_slot->state) { - case POWEROFF_STATE: - mutex_unlock(&p_slot->lock); + switch (info->req) { + case DISABLE_REQ: ctrl_dbg(p_slot->ctrl, "Disabling domain:bus:device=%04x:%02x:00\n", pci_domain_nr(p_slot->ctrl->pcie->port->subordinate), @@ -302,18 +303,22 @@ static void pciehp_power_thread(struct work_struct *work) pciehp_disable_slot(p_slot); mutex_lock(&p_slot->lock); p_slot->state = STATIC_STATE; - break; - case POWERON_STATE: mutex_unlock(&p_slot->lock); + break; + case ENABLE_REQ: + ctrl_dbg(p_slot->ctrl, + "Enabling domain:bus:device=%04x:%02x:00\n", + pci_domain_nr(p_slot->ctrl->pcie->port->subordinate), + p_slot->ctrl->pcie->port->subordinate->number); if (pciehp_enable_slot(p_slot)) pciehp_green_led_off(p_slot); mutex_lock(&p_slot->lock); p_slot->state = STATIC_STATE; + mutex_unlock(&p_slot->lock); break; default: break; } - mutex_unlock(&p_slot->lock); kfree(info); } @@ -336,9 +341,11 @@ void pciehp_queue_pushbutton_work(struct work_struct *work) switch (p_slot->state) { case BLINKINGOFF_STATE: p_slot->state = POWEROFF_STATE; + info->req = DISABLE_REQ; break; case BLINKINGON_STATE: p_slot->state = POWERON_STATE; + info->req = ENABLE_REQ; break; default: kfree(info); @@ -428,10 +435,13 @@ static void handle_surprise_event(struct slot *p_slot) INIT_WORK(&info->work, pciehp_power_thread); pciehp_get_adapter_status(p_slot, &getstatus); - if (!getstatus) + if (!getstatus) { p_slot->state = POWEROFF_STATE; - else + info->req = DISABLE_REQ; + } else { p_slot->state = POWERON_STATE; + info->req = ENABLE_REQ; + } queue_work(p_slot->wq, &info->work); } @@ -451,6 +461,7 @@ static void handle_link_event(struct slot *p_slot, u32 event) return; } info->p_slot = p_slot; + info->req = event == INT_LINK_UP ? ENABLE_REQ : DISABLE_REQ; INIT_WORK(&info->work, pciehp_power_thread); switch (p_slot->state) {