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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 <daniel@quora.org>
Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org
This commit is contained in:
Yijing Wang 2013-01-11 10:15:54 +08:00 committed by Bjorn Helgaas
parent d1c3ed669a
commit c2be6f93b3
4 changed files with 17 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/pci/hotplug/pciehp.h
View File

@ -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 {

11
drivers/pci/hotplug/pciehp_core.c
View File

@ -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 <dan.zink@compaq.com>, Greg Kroah-Hartman <greg@kroah.com>, Dely Sy <dely.l.sy@intel.com>"
@ -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");
}

8
drivers/pci/hotplug/pciehp_ctrl.c
View File

@ -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)

11
drivers/pci/hotplug/pciehp_hpc.c
View File

@ -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);
}