From 0d36c06afe8ac3510ebdd21eb023077cb28efde6 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Fri, 11 Jan 2013 12:21:15 -0700 Subject: [PATCH] PCI: shpchp: Use per-slot workqueues to avoid deadlock commit f652e7d2916fe2fcf9e7d709aa5b7476b431e2dd upstream. When we have an SHPC-capable bridge with a second SHPC-capable bridge below it, pushing the upstream bridge's attention button causes a deadlock. The deadlock happens because we use the shpchp_wq workqueue to run shpchp_pushbutton_thread(), which uses shpchp_disable_slot() to remove devices below the upstream bridge. When we remove the downstream bridge, we call shpc_remove(), the shpchp driver's .remove() method. That calls flush_workqueue(shpchp_wq), which deadlocks because the shpchp_pushbutton_thread() work item is still running. This patch avoids the deadlock by creating a workqueue for every slot and removing the single shared workqueue. Here's the call path that leads to the deadlock: shpchp_queue_pushbutton_work queue_work(shpchp_wq) # shpchp_pushbutton_thread ... shpchp_pushbutton_thread shpchp_disable_slot remove_board shpchp_unconfigure_device pci_stop_and_remove_bus_device ... shpc_remove # shpchp driver .remove method hpc_release_ctlr cleanup_slots flush_workqueue(shpchp_wq) This change is based on code inspection, since we don't have hardware with this topology. Based-on-patch-by: Yijing Wang Signed-off-by: Bjorn Helgaas [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/pci/hotplug/shpchp.h | 2 +- drivers/pci/hotplug/shpchp_core.c | 26 ++++++++++++++------------ drivers/pci/hotplug/shpchp_ctrl.c | 6 +++--- 3 files changed, 18 insertions(+), 16 deletions(-) diff --git a/drivers/pci/hotplug/shpchp.h b/drivers/pci/hotplug/shpchp.h index 0b9eb75482f4..2c2ac800c4a5 100644 --- a/drivers/pci/hotplug/shpchp.h +++ b/drivers/pci/hotplug/shpchp.h @@ -46,7 +46,6 @@ extern int shpchp_poll_mode; extern int shpchp_poll_time; extern int shpchp_debug; -extern struct workqueue_struct *shpchp_wq; #define dbg(format, arg...) \ do { \ @@ -90,6 +89,7 @@ struct slot { struct list_head slot_list; struct delayed_work work; /* work for button event */ struct mutex lock; + struct workqueue_struct *wq; u8 hp_slot; }; diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c index e2b35360d4ff..754a7cd6aba4 100644 --- a/drivers/pci/hotplug/shpchp_core.c +++ b/drivers/pci/hotplug/shpchp_core.c @@ -39,7 +39,6 @@ int shpchp_debug; int shpchp_poll_mode; int shpchp_poll_time; -struct workqueue_struct *shpchp_wq; #define DRIVER_VERSION "0.4" #define DRIVER_AUTHOR "Dan Zink , Greg Kroah-Hartman , Dely Sy " @@ -122,6 +121,14 @@ static int init_slots(struct controller *ctrl) slot->device = ctrl->slot_device_offset + i; slot->hpc_ops = ctrl->hpc_ops; slot->number = ctrl->first_slot + (ctrl->slot_num_inc * i); + + snprintf(name, sizeof(name), "shpchp-%d", slot->number); + slot->wq = alloc_workqueue(name, 0, 0); + if (!slot->wq) { + retval = -ENOMEM; + goto error_info; + } + mutex_init(&slot->lock); INIT_DELAYED_WORK(&slot->work, shpchp_queue_pushbutton_work); @@ -141,7 +148,7 @@ static int init_slots(struct controller *ctrl) if (retval) { ctrl_err(ctrl, "pci_hp_register failed with error %d\n", retval); - goto error_info; + goto error_slotwq; } get_power_status(hotplug_slot, &info->power_status); @@ -153,6 +160,8 @@ static int init_slots(struct controller *ctrl) } return 0; +error_slotwq: + destroy_workqueue(slot->wq); error_info: kfree(info); error_hpslot: @@ -173,7 +182,7 @@ void cleanup_slots(struct controller *ctrl) slot = list_entry(tmp, struct slot, slot_list); list_del(&slot->slot_list); cancel_delayed_work(&slot->work); - flush_workqueue(shpchp_wq); + destroy_workqueue(slot->wq); pci_hp_deregister(slot->hotplug_slot); } } @@ -356,18 +365,12 @@ static struct pci_driver shpc_driver = { static int __init shpcd_init(void) { - int retval = 0; - - shpchp_wq = alloc_ordered_workqueue("shpchp", 0); - if (!shpchp_wq) - return -ENOMEM; + int retval; retval = pci_register_driver(&shpc_driver); dbg("%s: pci_register_driver = %d\n", __func__, retval); info(DRIVER_DESC " version: " DRIVER_VERSION "\n"); - if (retval) { - destroy_workqueue(shpchp_wq); - } + return retval; } @@ -375,7 +378,6 @@ static void __exit shpcd_cleanup(void) { dbg("unload_shpchpd()\n"); pci_unregister_driver(&shpc_driver); - destroy_workqueue(shpchp_wq); info(DRIVER_DESC " version: " DRIVER_VERSION " unloaded\n"); } diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c index bba5b3e0bf8a..3ffc1b2b3932 100644 --- a/drivers/pci/hotplug/shpchp_ctrl.c +++ b/drivers/pci/hotplug/shpchp_ctrl.c @@ -51,7 +51,7 @@ 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(shpchp_wq, &info->work); + queue_work(p_slot->wq, &info->work); return 0; } @@ -456,7 +456,7 @@ void shpchp_queue_pushbutton_work(struct work_struct *work) kfree(info); goto out; } - queue_work(shpchp_wq, &info->work); + queue_work(p_slot->wq, &info->work); out: mutex_unlock(&p_slot->lock); } @@ -504,7 +504,7 @@ static void handle_button_press_event(struct slot *p_slot) p_slot->hpc_ops->green_led_blink(p_slot); p_slot->hpc_ops->set_attention_status(p_slot, 0); - queue_delayed_work(shpchp_wq, &p_slot->work, 5*HZ); + queue_delayed_work(p_slot->wq, &p_slot->work, 5*HZ); break; case BLINKINGOFF_STATE: case BLINKINGON_STATE: -- 2.39.5