[PATCH v7 0/4] PCI: pciehp, shpchp deadlock fixes

[PATCH v7 0/4] PCI: pciehp, shpchp deadlock fixes

[Bjorn Helgaas]

This is v7 of Yijing Wang's pciehp deadlock fix.  Here's the history of
previous postings:

    RFC Oct 31 2012
    v2  Nov  9 2012  use slot name, not device name
    v3  Nov 12 2012  create workqueues in pcie_init_slot(), pciehp-%u format
    v4  Nov 13 2012  use alloc_workqueue(name, 0, 0) again
    v5  Jan  9 2013  fix similar problem in shpchp
    v6  Jan 10 2013  add pciehp backtrace from Daniel 

This v7 series is functionally identical to v6.  In v7, I split the single
shpchp patch into three:

    PCI: shpchp: Make shpchp_wq non-ordered
    PCI: shpchp: Handle push button event asynchronously
    PCI: shpchp: Use per-slot workqueues to avoid deadlock

The first fixes what appears to be an error in e24dcbef93 ("shpchp: update
workqueue usage").  I split this out so Tejun could easily review it by itself.

I split the second out because it corresponds to a pciehp bugfix, 486b10b9f4
("PCI: pciehp: Handle push button event asynchronously"), that also affects
shpchp.

The "PCI: shpchp: Use per-slot workqueues to avoid deadlock" that remains
then corresponds exactly to Yijing's original pciehp deadlock fix.

I also rewrote the changelogs.

I propose to push the entire series for inclusion in v3.8, since it
fixes an easy-to-cause deadlock with Thunderbolt adapters.

---

Bjorn Helgaas (3):
      PCI: shpchp: Make shpchp_wq non-ordered
      PCI: shpchp: Handle push button event asynchronously
      PCI: shpchp: Use per-slot workqueues to avoid deadlock

Yijing Wang (1):
      PCI: pciehp: Use per-slot workqueues to avoid deadlock


 drivers/pci/hotplug/pciehp.h      |    2 +-
 drivers/pci/hotplug/pciehp_core.c |   11 ++---------
 drivers/pci/hotplug/pciehp_ctrl.c |    8 ++++----
 drivers/pci/hotplug/pciehp_hpc.c  |   11 ++++++++++-
 drivers/pci/hotplug/shpchp.h      |    3 +--
 drivers/pci/hotplug/shpchp_core.c |   36 ++++++++++++++----------------------
 drivers/pci/hotplug/shpchp_ctrl.c |    6 +++---
 7 files changed, 35 insertions(+), 42 deletions(-)

[PATCH v7 1/4] PCI: pciehp: Use per-slot workqueues to avoid deadlock

[Bjorn Helgaas]

From: Yijing Wang <wangyijing@huawei.com>

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
---
 drivers/pci/hotplug/pciehp.h      |    2 +-
 drivers/pci/hotplug/pciehp_core.c |   11 ++---------
 drivers/pci/hotplug/pciehp_ctrl.c |    8 ++++----
 drivers/pci/hotplug/pciehp_hpc.c  |   11 ++++++++++-
 4 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 26ffd3e..2c113de 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 916bf4f..939bd1d 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 <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");
 }
 
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 27f4429..38f0186 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 13b2eaf..5127f3f 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);
 }
 

[PATCH v7 2/4] PCI: shpchp: Make shpchp_wq non-ordered

[Bjorn Helgaas]

e24dcbef93 ("shpchp: update workqueue usage") was described as adding
non-ordered shpchp_wq, but it actually made it an *ordered* workqueue.

This patch changes shpchp_wq to be non-ordered, as described in the
e24dcbef93 commit log and as was done for pciehp by a827ea307b ("pciehp:
update workqueue usage").

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Tejun Heo <tj@kernel.org>
---
 drivers/pci/hotplug/shpchp_core.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c
index b6de307..59ca86c 100644
--- a/drivers/pci/hotplug/shpchp_core.c
+++ b/drivers/pci/hotplug/shpchp_core.c
@@ -366,7 +366,7 @@ static int __init shpcd_init(void)
 {
 	int retval = 0;
 
-	shpchp_wq = alloc_ordered_workqueue("shpchp", 0);
+	shpchp_wq = alloc_workqueue("shpchp", 0, 0);
 	if (!shpchp_wq)
 		return -ENOMEM;
 

[PATCH v7 3/4] PCI: shpchp: Handle push button event asynchronously

[Bjorn Helgaas]

Use non-ordered workqueue for attention button events.

Attention button events on each slot can be handled asynchronously. So
we should use non-ordered workqueue. This patch also removes ordered
workqueue in shpchp as a result.

486b10b9f4 ("PCI: pciehp: Handle push button event asynchronously") made
the same change to pciehp.  I split this out from a patch by Yijing Wang
<wangyijing@huawei.com> so we fix one thing at a time and to make the
shpchp history correspond more closely with the pciehp history.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
---
 drivers/pci/hotplug/shpchp.h      |    1 -
 drivers/pci/hotplug/shpchp_core.c |   10 ----------
 drivers/pci/hotplug/shpchp_ctrl.c |    2 +-
 3 files changed, 1 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/hotplug/shpchp.h b/drivers/pci/hotplug/shpchp.h
index ca64932..1b69d95 100644
--- a/drivers/pci/hotplug/shpchp.h
+++ b/drivers/pci/hotplug/shpchp.h
@@ -47,7 +47,6 @@ extern bool shpchp_poll_mode;
 extern int shpchp_poll_time;
 extern bool shpchp_debug;
 extern struct workqueue_struct *shpchp_wq;
-extern struct workqueue_struct *shpchp_ordered_wq;
 
 #define dbg(format, arg...)						\
 do {									\
diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c
index 59ca86c..3774e0d 100644
--- a/drivers/pci/hotplug/shpchp_core.c
+++ b/drivers/pci/hotplug/shpchp_core.c
@@ -40,7 +40,6 @@ bool shpchp_debug;
 bool shpchp_poll_mode;
 int shpchp_poll_time;
 struct workqueue_struct *shpchp_wq;
-struct workqueue_struct *shpchp_ordered_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>"
@@ -181,7 +180,6 @@ void cleanup_slots(struct controller *ctrl)
 		list_del(&slot->slot_list);
 		cancel_delayed_work(&slot->work);
 		flush_workqueue(shpchp_wq);
-		flush_workqueue(shpchp_ordered_wq);
 		pci_hp_deregister(slot->hotplug_slot);
 	}
 }
@@ -370,17 +368,10 @@ static int __init shpcd_init(void)
 	if (!shpchp_wq)
 		return -ENOMEM;
 
-	shpchp_ordered_wq = alloc_ordered_workqueue("shpchp_ordered", 0);
-	if (!shpchp_ordered_wq) {
-		destroy_workqueue(shpchp_wq);
-		return -ENOMEM;
-	}
-
 	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_ordered_wq);
 		destroy_workqueue(shpchp_wq);
 	}
 	return retval;
@@ -390,7 +381,6 @@ static void __exit shpcd_cleanup(void)
 {
 	dbg("unload_shpchpd()\n");
 	pci_unregister_driver(&shpc_driver);
-	destroy_workqueue(shpchp_ordered_wq);
 	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 f9b5a52..fd2cae9 100644
--- a/drivers/pci/hotplug/shpchp_ctrl.c
+++ b/drivers/pci/hotplug/shpchp_ctrl.c
@@ -453,7 +453,7 @@ void shpchp_queue_pushbutton_work(struct work_struct *work)
 		kfree(info);
 		goto out;
 	}
-	queue_work(shpchp_ordered_wq, &info->work);
+	queue_work(shpchp_wq, &info->work);
  out:
 	mutex_unlock(&p_slot->lock);
 }

[PATCH v7 4/4] PCI: shpchp: Use per-slot workqueues to avoid deadlock

[Bjorn Helgaas]

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 <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org
---
 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 1b69d95..b849f995 100644
--- a/drivers/pci/hotplug/shpchp.h
+++ b/drivers/pci/hotplug/shpchp.h
@@ -46,7 +46,6 @@
 extern bool shpchp_poll_mode;
 extern int shpchp_poll_time;
 extern bool 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 3774e0d..3100c52 100644
--- a/drivers/pci/hotplug/shpchp_core.c
+++ b/drivers/pci/hotplug/shpchp_core.c
@@ -39,7 +39,6 @@
 bool shpchp_debug;
 bool shpchp_poll_mode;
 int shpchp_poll_time;
-struct workqueue_struct *shpchp_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>"
@@ -128,6 +127,14 @@ 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);
 
@@ -147,7 +154,7 @@ 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);
@@ -159,6 +166,8 @@ static int init_slots(struct controller *ctrl)
 	}
 
 	return 0;
+error_slotwq:
+	destroy_workqueue(slot->wq);
 error_info:
 	kfree(info);
 error_hpslot:
@@ -179,7 +188,7 @@ 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);
 	}
 }
@@ -362,18 +371,12 @@ static struct pci_driver shpc_driver = {
 
 static int __init shpcd_init(void)
 {
-	int retval = 0;
-
-	shpchp_wq = alloc_workqueue("shpchp", 0, 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;
 }
 
@@ -381,7 +384,6 @@ 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 fd2cae9..5849927 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;
 }
@@ -453,7 +453,7 @@ 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);
 }
@@ -501,7 +501,7 @@ 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:

Re: [PATCH v7 0/4] PCI: pciehp, shpchp deadlock fixes

[Yijing Wang]

On 2013/1/14 7:27, Bjorn Helgaas wrote:
> This is v7 of Yijing Wang's pciehp deadlock fix.  Here's the history of
> previous postings:
> 
>     RFC Oct 31 2012
>     v2  Nov  9 2012  use slot name, not device name
>     v3  Nov 12 2012  create workqueues in pcie_init_slot(), pciehp-%u format
>     v4  Nov 13 2012  use alloc_workqueue(name, 0, 0) again
>     v5  Jan  9 2013  fix similar problem in shpchp
>     v6  Jan 10 2013  add pciehp backtrace from Daniel 
> 
> This v7 series is functionally identical to v6.  In v7, I split the single
> shpchp patch into three:
> 
>     PCI: shpchp: Make shpchp_wq non-ordered
>     PCI: shpchp: Handle push button event asynchronously
>     PCI: shpchp: Use per-slot workqueues to avoid deadlock
> 

Nice, split the single patch into three will make the log clearer about the
code changes.

> The first fixes what appears to be an error in e24dcbef93 ("shpchp: update
> workqueue usage").  I split this out so Tejun could easily review it by itself.
> 
> I split the second out because it corresponds to a pciehp bugfix, 486b10b9f4
> ("PCI: pciehp: Handle push button event asynchronously"), that also affects
> shpchp.
> 
> The "PCI: shpchp: Use per-slot workqueues to avoid deadlock" that remains
> then corresponds exactly to Yijing's original pciehp deadlock fix.
> 
> I also rewrote the changelogs.
> 
> I propose to push the entire series for inclusion in v3.8, since it
> fixes an easy-to-cause deadlock with Thunderbolt adapters.
> 
> ---
> 
> Bjorn Helgaas (3):
>       PCI: shpchp: Make shpchp_wq non-ordered
>       PCI: shpchp: Handle push button event asynchronously
>       PCI: shpchp: Use per-slot workqueues to avoid deadlock
> 
> Yijing Wang (1):
>       PCI: pciehp: Use per-slot workqueues to avoid deadlock
> 
> 
>  drivers/pci/hotplug/pciehp.h      |    2 +-
>  drivers/pci/hotplug/pciehp_core.c |   11 ++---------
>  drivers/pci/hotplug/pciehp_ctrl.c |    8 ++++----
>  drivers/pci/hotplug/pciehp_hpc.c  |   11 ++++++++++-
>  drivers/pci/hotplug/shpchp.h      |    3 +--
>  drivers/pci/hotplug/shpchp_core.c |   36 ++++++++++++++----------------------
>  drivers/pci/hotplug/shpchp_ctrl.c |    6 +++---
>  7 files changed, 35 insertions(+), 42 deletions(-)
> 
> 


-- 
Thanks!
Yijing

Re: [PATCH v7 2/4] PCI: shpchp: Make shpchp_wq non-ordered

[Tejun Heo]

Hello,

On Sun, Jan 13, 2013 at 04:27:43PM -0700, Bjorn Helgaas wrote:
> e24dcbef93 ("shpchp: update workqueue usage") was described as adding
> non-ordered shpchp_wq, but it actually made it an *ordered* workqueue.
> 
> This patch changes shpchp_wq to be non-ordered, as described in the
> e24dcbef93 commit log and as was done for pciehp by a827ea307b ("pciehp:
> update workqueue usage").
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> CC: Tejun Heo <tj@kernel.org>

Yeap, my mistake.

Acked-by: Tejun Heo <tj@kernel.org>

Thanks!

-- 
tejun