Re: [PATCH 1/2] PCI, pciehp: make every slot have its own workqueue to avoid deadlock

[Yijing Wang <wangyijing@huawei.com>]

I'm very sorry, forgeted to add Daniel J Blueman reported-by, I updated this patch to
add reported-by and cc stable branch.


Thanks!
Yijing.

On 2013/1/10 11:22, Yijing Wang wrote:
> Currently, pciehp use global pciehp_wq to handle hotplug event from hardware.
> Hot remove path will be blocked if a hotplug slot connected a IO-BOX(composed of PCIe
> Switch and some slots which support hotplug). Because The hot removed work was queued
> into pciehp_wq. But in the hot-remove path, pciehp driver would flush pciehp_wq when
> the pcie port(support pciehp) was removed. In this case the hot-remove path blocked.
> This patch remove the global pciehp_wq and create a new workqueue for every slot to
> avoid above problem.
> call path:
> 1. Hot-removal request comes to slot A(eg. 0000:40:07.0 as bellow)
> 2. Pciehp driver queue hot-remove work into global workqueue "pciehp_wq"
> 3. Hot-remove work call pci_stop_and_remove_bus_device() to remove child devices.
> 4. Unregister and remove Pcie port device slot B(eg. 0000:47:15.0).
> 5. To remove pcie port device, flush_workqueue(pciehp_wq) will be called.
> 6. Deaklock <== hot-removal work is in progress.
> 
> -+-[0000:40]-+-00.0-[0000:41]--
>  |           +-01.0-[0000:42]--+-00.0  Intel Corporation 82576 Gigabit Network Connection
>  |           |                 \-00.1  Intel Corporation 82576 Gigabit Network Connection
>  |           +-03.0-[0000:43]----00.0  LSI Logic / Symbios Logic SAS1064ET PCI-Express Fusion-MPT SAS
>  |           +-04.0-[0000:44]--
>  |           +-05.0-[0000:45]--
>  |           +-07.0-[0000:46-4f]----00.0-[0000:47-4f]--+-04.0-[0000:48-49]----00.0-[0000:49]--
>  |           |(slot A)                                 +-08.0-[0000:4a]--
>  |           |                                         +-09.0-[0000:4b]--
>  |           |                                         +-10.0-[0000:4c]--
>  |           |                                         +-11.0-[0000:4d]--
>  |           |                                         +-14.0-[0000:4e]--
>  |           |                                         \-15.0-[0000:4f]--+-00.0  Intel Corporation 82576 Gigabit Network Connection
>  |           |                                         (slot B)          \-00.1  Intel Corporation 82576 Gigabit Network Connection
> 
> Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> ---
>  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);
>  }
>  
> 


-- 
Thanks!
Yijing