Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751729AbdLLIiY (ORCPT ); Tue, 12 Dec 2017 03:38:24 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:11971 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750715AbdLLIiU (ORCPT ); Tue, 12 Dec 2017 03:38:20 -0500 From: Xiongfeng Wang To: , CC: , , , , Subject: [RFC PATCH][resend] pciehp: fix a race between pciehp and removing operations by sysfs Date: Tue, 12 Dec 2017 16:29:44 +0800 Message-ID: <1513067384-10914-1-git-send-email-wangxiongfeng2@huawei.com> X-Mailer: git-send-email 1.7.12.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.102.37] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020202.5A2F9576.00AF,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: defc94be521d4adc054f05ddbbc365f5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4675 Lines: 104 When the Attention button on a PCIE slot is pressed, 5 seconds later, pciehp_power_thread() will be scheduled on slot->wq. This function will get a global mutex lock 'pci_rescan_remove_lock' in pciehp_unconfigure_device(). At the same time, we remove the pcie port by sysfs, which results in pci_stop_and_remove_bus_device_locked() called. This function will get the global mutex lock 'pci_rescan_remove_lock', and then release the struct 'ctrl', which will wait until the work_struct on slot->wq is finished. If pci_stop_and_remove_bus_device_locked() got the mutex lock, and before it drains workqueue slot->wq, pciehp_power_thread() is scheduled on slot->wq and tries to get the mutex lock. Then pci_stop_and_remove_bus_device_locked() tries to drain workqueue slot->wq and wait until work struct 'pciehp_power_thread()' is finished. Then a hung_task happens. This patch solve this problem by schedule 'pciehp_power_thread()' on a system workqueue instead of slot->wq. The Call Trace we got is as following. INFO: task kworker/0:2:4413 blocked for more than 120 seconds. Tainted: P W O 4.12.0-rc1 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:2 D 0 4413 2 0x00000000 Workqueue: pciehp-0 pciehp_power_thread Call trace: [] __switch_to+0x94/0xa8 [] __schedule+0x1b0/0x708 [] schedule+0x40/0xa4 [] schedule_preempt_disabled+0x28/0x40 [] __mutex_lock.isra.8+0x148/0x50c [] __mutex_lock_slowpath+0x24/0x30 [] mutex_lock+0x48/0x54 [] pci_lock_rescan_remove+0x20/0x28 [] pciehp_unconfigure_device+0x54/0x1cc [] pciehp_disable_slot+0x4c/0xbc [] pciehp_power_thread+0xa0/0xb8 [] process_one_work+0x13c/0x3f8 [] worker_thread+0x60/0x3e4 [] kthread+0x10c/0x138 [] ret_from_fork+0x10/0x50 INFO: task bash:31732 blocked for more than 120 seconds. Tainted: P W O 4.12.0-rc1 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. bash D 0 31732 1 0x00000009 Call trace: [] __switch_to+0x94/0xa8 [] __schedule+0x1b0/0x708 [] schedule+0x40/0xa4 [] schedule_timeout+0x1a0/0x340 [] wait_for_common+0x108/0x1bc [] wait_for_completion+0x28/0x34 [] flush_workqueue+0x130/0x488 [] drain_workqueue+0xc4/0x164 [] destroy_workqueue+0x28/0x1f4 [] pciehp_release_ctrl+0x34/0xe0 [] pciehp_remove+0x30/0x3c [] pcie_port_remove_service+0x3c/0x54 [] device_release_driver_internal+0x150/0x1d0 [] device_release_driver+0x28/0x34 [] bus_remove_device+0xe0/0x11c [] device_del+0x200/0x304 [] device_unregister+0x20/0x38 [] remove_iter+0x44/0x54 [] device_for_each_child+0x4c/0x90 [] pcie_port_device_remove+0x2c/0x48 [] pcie_portdrv_remove+0x60/0x6c [] pci_device_remove+0x48/0x110 [] device_release_driver_internal+0x150/0x1d0 [] device_release_driver+0x28/0x34 [] pci_stop_bus_device+0x9c/0xac [] pci_stop_and_remove_bus_device_locked+0x24/0x3c [] remove_store+0x74/0x80 [] dev_attr_store+0x44/0x5c [] sysfs_kf_write+0x5c/0x74 [] kernfs_fop_write+0xcc/0x1dc [] __vfs_write+0x48/0x13c [] vfs_write+0xa8/0x198 [] SyS_write+0x54/0xb0 [] el0_svc_naked+0x24/0x28 Signed-off-by: Xiongfeng Wang --- drivers/pci/hotplug/pciehp_ctrl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 83f3d4a..9d39d85 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -221,7 +221,7 @@ static void pciehp_queue_power_work(struct slot *p_slot, int req) info->p_slot = p_slot; INIT_WORK(&info->work, pciehp_power_thread); info->req = req; - queue_work(p_slot->wq, &info->work); + schedule_work(&info->work); } void pciehp_queue_pushbutton_work(struct work_struct *work) -- 1.7.12.4