From: Yijing Wang Date: Fri, 11 Jan 2013 02:15:54 +0000 (+0800) Subject: PCI: pciehp: Use per-slot workqueues to avoid deadlock X-Git-Tag: firefly_0821_release~3680^2~1136^2~3^2~3 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c2be6f93b383c873a4f9d521afa49b1b67d06085;p=firefly-linux-kernel-4.4.55.git PCI: pciehp: Use per-slot workqueues to avoid deadlock When we have a hotplug-capable PCIe port with a second hotplug-capable PCIe port below it, removing the device below the upstream port causes a deadlock. The deadlock happens because we use the pciehp_wq workqueue to run pciehp_power_thread(), which uses pciehp_disable_slot() to remove devices below the upstream port. When we remove the downstream PCIe port, we call pciehp_remove(), the pciehp driver's .remove() method. That calls flush_workqueue(pciehp_wq), which deadlocks because the pciehp_power_thread() work item is still running. This patch avoids the deadlock by creating a workqueue for every PCIe port and removing the single shared workqueue. Here's the call path that leads to the deadlock: pciehp_queue_pushbutton_work queue_work(pciehp_wq) # queue pciehp_power_thread ... pciehp_power_thread pciehp_disable_slot remove_board pciehp_unconfigure_device pci_stop_and_remove_bus_device ... pciehp_remove # pciehp driver .remove method pciehp_release_ctrl pcie_cleanup_slot flush_workqueue(pciehp_wq) This is fairly urgent because it can be caused by simply unplugging a Thunderbolt adapter, as reported by Daniel below. [bhelgaas: changelog] Reference: http://lkml.kernel.org/r/CAMVG2ssiRgcTD1bej2tkUUfsWmpL5eNtPcNif9va2-Gzb2u8nQ@mail.gmail.com Reported-and-tested-by: Daniel J Blueman Reviewed-by: Kenji Kaneshige Signed-off-by: Yijing Wang Signed-off-by: Bjorn Helgaas CC: stable@vger.kernel.org --- diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h index 26ffd3e3fb74..2c113de94323 100644 --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -44,7 +44,6 @@ extern bool pciehp_poll_mode; extern int pciehp_poll_time; extern bool pciehp_debug; extern bool pciehp_force; -extern struct workqueue_struct *pciehp_wq; #define dbg(format, arg...) \ do { \ @@ -78,6 +77,7 @@ struct slot { struct hotplug_slot *hotplug_slot; struct delayed_work work; /* work for button event */ struct mutex lock; + struct workqueue_struct *wq; }; struct event_info { diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c index 916bf4f53aba..939bd1d4b5b1 100644 --- a/drivers/pci/hotplug/pciehp_core.c +++ b/drivers/pci/hotplug/pciehp_core.c @@ -42,7 +42,6 @@ bool pciehp_debug; bool pciehp_poll_mode; int pciehp_poll_time; bool pciehp_force; -struct workqueue_struct *pciehp_wq; #define DRIVER_VERSION "0.4" #define DRIVER_AUTHOR "Dan Zink , Greg Kroah-Hartman , Dely Sy " @@ -340,18 +339,13 @@ static int __init pcied_init(void) { int retval = 0; - pciehp_wq = alloc_workqueue("pciehp", 0, 0); - if (!pciehp_wq) - return -ENOMEM; - pciehp_firmware_init(); retval = pcie_port_service_register(&hpdriver_portdrv); dbg("pcie_port_service_register = %d\n", retval); info(DRIVER_DESC " version: " DRIVER_VERSION "\n"); - if (retval) { - destroy_workqueue(pciehp_wq); + if (retval) dbg("Failure to register service\n"); - } + return retval; } @@ -359,7 +353,6 @@ static void __exit pcied_cleanup(void) { dbg("unload_pciehpd()\n"); pcie_port_service_unregister(&hpdriver_portdrv); - destroy_workqueue(pciehp_wq); info(DRIVER_DESC " version: " DRIVER_VERSION " unloaded\n"); } diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 27f44295a657..38f018679175 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -49,7 +49,7 @@ static int queue_interrupt_event(struct slot *p_slot, u32 event_type) info->p_slot = p_slot; INIT_WORK(&info->work, interrupt_event_handler); - queue_work(pciehp_wq, &info->work); + queue_work(p_slot->wq, &info->work); return 0; } @@ -344,7 +344,7 @@ void pciehp_queue_pushbutton_work(struct work_struct *work) kfree(info); goto out; } - queue_work(pciehp_wq, &info->work); + queue_work(p_slot->wq, &info->work); out: mutex_unlock(&p_slot->lock); } @@ -377,7 +377,7 @@ static void handle_button_press_event(struct slot *p_slot) if (ATTN_LED(ctrl)) pciehp_set_attention_status(p_slot, 0); - queue_delayed_work(pciehp_wq, &p_slot->work, 5*HZ); + queue_delayed_work(p_slot->wq, &p_slot->work, 5*HZ); break; case BLINKINGOFF_STATE: case BLINKINGON_STATE: @@ -439,7 +439,7 @@ static void handle_surprise_event(struct slot *p_slot) else p_slot->state = POWERON_STATE; - queue_work(pciehp_wq, &info->work); + queue_work(p_slot->wq, &info->work); } static void interrupt_event_handler(struct work_struct *work) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 13b2eaf7ba43..5127f3f41821 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -773,23 +773,32 @@ static void pcie_shutdown_notification(struct controller *ctrl) static int pcie_init_slot(struct controller *ctrl) { struct slot *slot; + char name[32]; slot = kzalloc(sizeof(*slot), GFP_KERNEL); if (!slot) return -ENOMEM; + snprintf(name, sizeof(name), "pciehp-%u", PSN(ctrl)); + slot->wq = alloc_workqueue(name, 0, 0); + if (!slot->wq) + goto abort; + slot->ctrl = ctrl; mutex_init(&slot->lock); INIT_DELAYED_WORK(&slot->work, pciehp_queue_pushbutton_work); ctrl->slot = slot; return 0; +abort: + kfree(slot); + return -ENOMEM; } static void pcie_cleanup_slot(struct controller *ctrl) { struct slot *slot = ctrl->slot; cancel_delayed_work(&slot->work); - flush_workqueue(pciehp_wq); + destroy_workqueue(slot->wq); kfree(slot); }