Let me confirm the problem. My understanding of the problem is below.
Is my understanding correct?
- Your hardware has nested PCIe hotplug slots like below.
--<slot A>--<Slot B>
- Hot-removal request (attention button event) comes to <slot A>
- Pciehp driver queue the hot-removal work
- This hot-removal work try to remove <slot B>
- To remove <slot B>, pciehp flush the pciehp_wq, but it never finishes
because hot-removal work is in progress. ===> deadlock
Regards,
Kenji Kaneshige
> -----Original Message-----
> From: Yijing Wang [mailto:wangyijing@xxxxxxxxxx]
> Sent: Wednesday, October 31, 2012 4:11 PM
> To: Bjorn Helgaas; Yinghai Lu; Kaneshige, Kenji/金重 憲治; Rafael; Rusty
> Russell; Mauro Carvalho Chehab; Oliver Neukum
> Cc: linux-pci@xxxxxxxxxxxxxxx; Hanjun Guo; jiang.liu@xxxxxxxxxx; Yijing
> Wang
> Subject: [RFC][PATCH] PCI, pciehp: make every slot have its own workqueue
> to avoid deadlock
>
> 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, eg.PLX8696). 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.
>
> -+-[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]--
> | |(hotplug slot)
> +-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
> | | (hotplug slot)
> \-00.1 Intel Corporation 82576 Gigabit Network Connection
>
>
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> ---
> 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 | 14 ++++++++++++--
> 4 files changed, 19 insertions(+), 16 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..0914211 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@xxxxxxxxxx>, Greg
> Kroah-Hartman <greg@xxxxxxxxx>, Dely Sy <dely.l.sy@xxxxxxxxx>"
> @@ -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..8e5e571 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -773,23 +773,33 @@ 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), "pciehpd_%s",
> + pci_name(ctrl->pcie->port));
> + slot->wq = create_singlethread_workqueue(name);
> + 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 -1;
> }
>
> static void pcie_cleanup_slot(struct controller *ctrl)
> {
> struct slot *slot = ctrl->slot;
> cancel_delayed_work(&slot->work);
> - flush_workqueue(pciehp_wq);
> + flush_workqueue(slot->wq);
> + destroy_workqueue(slot->wq);
> kfree(slot);
> }
>
> --
> 1.7.1
>
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