From patchwork Tue Jun 18 12:50:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mika Westerberg X-Patchwork-Id: 1117870 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.intel.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45Sny04dySz9sDX for ; Tue, 18 Jun 2019 22:51:04 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726739AbfFRMu6 (ORCPT ); Tue, 18 Jun 2019 08:50:58 -0400 Received: from mga11.intel.com ([192.55.52.93]:45248 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725913AbfFRMu5 (ORCPT ); Tue, 18 Jun 2019 08:50:57 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Jun 2019 05:50:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,389,1557212400"; d="scan'208";a="161736531" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga007.fm.intel.com with ESMTP; 18 Jun 2019 05:50:52 -0700 Received: by black.fi.intel.com (Postfix, from userid 1001) id 7B692177; Tue, 18 Jun 2019 15:50:51 +0300 (EEST) From: Mika Westerberg To: Bjorn Helgaas , "Rafael J. Wysocki" Cc: Lukas Wunner , Keith Busch , Andy Shevchenko , Frederick Lawler , Mika Westerberg , "Gustavo A . R . Silva" , Sinan Kaya , Kai Heng Feng , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] PCI: pciehp: Prevent deadlock on disconnect Date: Tue, 18 Jun 2019 15:50:51 +0300 Message-Id: <20190618125051.2382-2-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190618125051.2382-1-mika.westerberg@linux.intel.com> References: <20190618125051.2382-1-mika.westerberg@linux.intel.com> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org If there are more than one PCIe switch with hotplug downstream ports hot-removing them leads to a following deadlock: INFO: task irq/126-pciehp:198 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. irq/126-pciehp D 0 198 2 0x80000000 Call Trace: __schedule+0x2a2/0x880 schedule+0x2c/0x80 schedule_timeout+0x246/0x350 ? ttwu_do_activate+0x67/0x90 wait_for_completion+0xb7/0x140 ? wake_up_q+0x80/0x80 kthread_stop+0x49/0x110 __free_irq+0x15c/0x2a0 free_irq+0x32/0x70 pcie_shutdown_notification+0x2f/0x50 pciehp_remove+0x27/0x50 pcie_port_remove_service+0x36/0x50 device_release_driver_internal+0x18c/0x250 device_release_driver+0x12/0x20 bus_remove_device+0xec/0x160 device_del+0x13b/0x350 ? pcie_port_find_device+0x60/0x60 device_unregister+0x1a/0x60 remove_iter+0x1e/0x30 device_for_each_child+0x56/0x90 pcie_port_device_remove+0x22/0x40 pcie_portdrv_remove+0x20/0x60 pci_device_remove+0x3e/0xc0 device_release_driver_internal+0x18c/0x250 device_release_driver+0x12/0x20 pci_stop_bus_device+0x6f/0x90 pci_stop_bus_device+0x31/0x90 pci_stop_and_remove_bus_device+0x12/0x20 pciehp_unconfigure_device+0x88/0x140 pciehp_disable_slot+0x6a/0x110 pciehp_handle_presence_or_link_change+0x263/0x400 pciehp_ist+0x1c9/0x1d0 ? irq_forced_thread_fn+0x80/0x80 irq_thread_fn+0x24/0x60 irq_thread+0xeb/0x190 ? irq_thread_fn+0x60/0x60 kthread+0x120/0x140 ? irq_thread_check_affinity+0xf0/0xf0 ? kthread_park+0x90/0x90 ret_from_fork+0x35/0x40 INFO: task irq/190-pciehp:2288 blocked for more than 120 seconds. irq/190-pciehp D 0 2288 2 0x80000000 Call Trace: __schedule+0x2a2/0x880 schedule+0x2c/0x80 schedule_preempt_disabled+0xe/0x10 __mutex_lock.isra.9+0x2e0/0x4d0 ? __mutex_lock_slowpath+0x13/0x20 __mutex_lock_slowpath+0x13/0x20 mutex_lock+0x2c/0x30 pci_lock_rescan_remove+0x15/0x20 pciehp_unconfigure_device+0x4d/0x140 pciehp_disable_slot+0x6a/0x110 pciehp_handle_presence_or_link_change+0x263/0x400 pciehp_ist+0x1c9/0x1d0 ? irq_forced_thread_fn+0x80/0x80 irq_thread_fn+0x24/0x60 irq_thread+0xeb/0x190 ? irq_thread_fn+0x60/0x60 kthread+0x120/0x140 ? irq_thread_check_affinity+0xf0/0xf0 ? kthread_park+0x90/0x90 ret_from_fork+0x35/0x40 What happens here is that the whole hierarchy is runtime resumed and the parent PCIe downstream port, who got the hot-remove event, starts removing devices below it taking pci_lock_rescan_remove() lock. When the child PCIe port is runtime resumed it calls pciehp_check_presence() which ends up calling pciehp_card_present() and pciehp_check_link_active(). Both of these read their parts of PCIe config space by calling helper function pcie_capability_read_word(). Now, this function notices that the underlying device is already gone and returns PCIBIOS_DEVICE_NOT_FOUND with the capability value set to 0. When pciehp gets this value it thinks that its child device is also hot-removed and schedules its IRQ thread to handle the event. The deadlock happens when the child's IRQ thread runs and tries to acquire pci_lock_rescan_remove() which is already taken by the parent and the parent waits for the child's IRQ thread to finish. We can prevent this from happening by checking the return value of pcie_capability_read_word() and if it is PCIBIOS_DEVICE_NOT_FOUND stop performing any hot-removal activities. Signed-off-by: Mika Westerberg --- Hi, This is really annoying issue and triggers 100% if you have more than one Thunderbolt device connected in a daisy chain (each of them include PCIe switch with hotplug downstream ports). Previously there has been discussion around the issue but so it remains unfixed. Since more and more systems out there are relying on native PCIe hotplug, I think we need to do something about it so here's my attempt :) drivers/pci/hotplug/pciehp.h | 6 +++--- drivers/pci/hotplug/pciehp_core.c | 11 ++++++++--- drivers/pci/hotplug/pciehp_ctrl.c | 4 ++-- drivers/pci/hotplug/pciehp_hpc.c | 32 +++++++++++++++++++++++-------- 4 files changed, 37 insertions(+), 16 deletions(-) diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h index 8c51a04b8083..81c514ab9518 100644 --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -173,10 +173,10 @@ int pciehp_query_power_fault(struct controller *ctrl); void pciehp_green_led_on(struct controller *ctrl); void pciehp_green_led_off(struct controller *ctrl); void pciehp_green_led_blink(struct controller *ctrl); -bool pciehp_card_present(struct controller *ctrl); -bool pciehp_card_present_or_link_active(struct controller *ctrl); +int pciehp_card_present(struct controller *ctrl); +int pciehp_card_present_or_link_active(struct controller *ctrl); int pciehp_check_link_status(struct controller *ctrl); -bool pciehp_check_link_active(struct controller *ctrl); +int pciehp_check_link_active(struct controller *ctrl); void pciehp_release_ctrl(struct controller *ctrl); int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot); diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c index 3f8c13ddb3e8..1b015dd11914 100644 --- a/drivers/pci/hotplug/pciehp_core.c +++ b/drivers/pci/hotplug/pciehp_core.c @@ -134,10 +134,15 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value) { struct controller *ctrl = to_ctrl(hotplug_slot); struct pci_dev *pdev = ctrl->pcie->port; + int ret; pci_config_pm_runtime_get(pdev); - *value = pciehp_card_present_or_link_active(ctrl); + ret = pciehp_card_present_or_link_active(ctrl); pci_config_pm_runtime_put(pdev); + if (ret < 0) + return ret; + + *value = ret; return 0; } @@ -153,13 +158,13 @@ static int get_adapter_status(struct hotplug_slot *hotplug_slot, u8 *value) */ static void pciehp_check_presence(struct controller *ctrl) { - bool occupied; + int occupied; down_read(&ctrl->reset_lock); mutex_lock(&ctrl->state_lock); occupied = pciehp_card_present_or_link_active(ctrl); - if ((occupied && (ctrl->state == OFF_STATE || + if ((occupied > 0 && (ctrl->state == OFF_STATE || ctrl->state == BLINKINGON_STATE)) || (!occupied && (ctrl->state == ON_STATE || ctrl->state == BLINKINGOFF_STATE))) diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 631ced0ab28a..5a433cc8621f 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -221,7 +221,7 @@ void pciehp_handle_disable_request(struct controller *ctrl) void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) { - bool present, link_active; + int present, link_active; /* * If the slot is on and presence or link has changed, turn it off. @@ -252,7 +252,7 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events) mutex_lock(&ctrl->state_lock); present = pciehp_card_present(ctrl); link_active = pciehp_check_link_active(ctrl); - if (!present && !link_active) { + if (present <= 0 && link_active <= 0) { mutex_unlock(&ctrl->state_lock); return; } diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index bd990e3371e3..1f918b043adb 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -201,13 +201,16 @@ static void pcie_write_cmd_nowait(struct controller *ctrl, u16 cmd, u16 mask) pcie_do_write_cmd(ctrl, cmd, mask, false); } -bool pciehp_check_link_active(struct controller *ctrl) +int pciehp_check_link_active(struct controller *ctrl) { struct pci_dev *pdev = ctrl_dev(ctrl); u16 lnk_status; - bool ret; + int ret; + + ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status); + if (ret == PCIBIOS_DEVICE_NOT_FOUND) + return -ENODEV; - pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status); ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA); if (ret) @@ -373,13 +376,17 @@ void pciehp_get_latch_status(struct controller *ctrl, u8 *status) *status = !!(slot_status & PCI_EXP_SLTSTA_MRLSS); } -bool pciehp_card_present(struct controller *ctrl) +int pciehp_card_present(struct controller *ctrl) { struct pci_dev *pdev = ctrl_dev(ctrl); u16 slot_status; + int ret; - pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); - return slot_status & PCI_EXP_SLTSTA_PDS; + ret = pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status); + if (ret == PCIBIOS_DEVICE_NOT_FOUND) + return -ENODEV; + + return !!(slot_status & PCI_EXP_SLTSTA_PDS); } /** @@ -390,10 +397,19 @@ bool pciehp_card_present(struct controller *ctrl) * Presence Detect State bit, this helper also returns true if the Link Active * bit is set. This is a concession to broken hotplug ports which hardwire * Presence Detect State to zero, such as Wilocity's [1ae9:0200]. + * + * Returns: %1 if the slot is occupied and %0 if it is not. If the hotplug + * port is not present anymore returns %-ENODEV. */ -bool pciehp_card_present_or_link_active(struct controller *ctrl) +int pciehp_card_present_or_link_active(struct controller *ctrl) { - return pciehp_card_present(ctrl) || pciehp_check_link_active(ctrl); + int ret; + + ret = pciehp_card_present(ctrl); + if (ret) + return ret; + + return pciehp_check_link_active(ctrl); } int pciehp_query_power_fault(struct controller *ctrl)