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authorBjorn Helgaas <bhelgaas@google.com>2013-01-11 12:21:15 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-01-27 20:49:01 -0800
commit8de1accd5386dd947044890963ccfc83e5e28cb0 (patch)
tree9d6c97b784d87e68f38bccf0c836359b622c2c1d
parent6b816c6a5e4f45cff374ca827aeaf1be2f0b32a9 (diff)
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 <wangyijing@huawei.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/pci/hotplug/shpchp.h2
-rw-r--r--drivers/pci/hotplug/shpchp_core.c25
-rw-r--r--drivers/pci/hotplug/shpchp_ctrl.c6
3 files changed, 17 insertions, 16 deletions
diff --git a/drivers/pci/hotplug/shpchp.h b/drivers/pci/hotplug/shpchp.h
index 1b69d955a31..b849f995075 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 8c6d6454175..ea15fdc52af 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 +371,11 @@ 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;
}
@@ -381,7 +383,6 @@ 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 fd2cae9eb6c..58499277903 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: