linux-kernel - Re: [RFC PATCH 1/2] PCI: correctly flush workqueue when destroy pcie hotplug controller

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Date:	Tue, 10 Apr 2012 19:43:34 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Jiang Liu <liuj97@...il.com>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	matsumoto.hiroo@...fujitsu.com,
	Keping Chen <chenkeping@...wei.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] PCI: correctly flush workqueue when destroy pcie
 hotplug controller

I think you're rignt.

Reviewed-by: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>

(2012/04/08 3:18), Jiang Liu wrote:
> When destroying a PCIe hotplug controller, all work items associated with
> that controller should be flushed.  Function pcie_cleanup_slot() calls
> cancel_delayed_work() and flush_workqueue() to achieve that.
> Function flush_workqueue() will flush all work items already submitted,
> but new work items submitted by those already submitted work items may
> still be in live state when returning from flush_workqueue().
> 
> For the extreme case, pciehp driver may expierence following calling path:
> 1) pcie_isr() ->  pciehp_handle_xxx() ->  queue_interrupt_event()->queue_work()
> 2) interrupt_event_handler() ->  handle_button_press_event() ->
>     queue_delayed_work()
> 3) pciehp_queue_pushbutton_work() ->  queue_work()
> 
> So enhance pcie_cleanup_slot() to correctly flush workqueue when destroying
> PCIe hotplug controller.
> 
> Signed-off-by: Jiang Liu<jiang.liu@...wei.com>
> ---
>   drivers/pci/hotplug/pciehp_hpc.c |   13 ++++++++++++-
>   1 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index d4fa705..9a48a51 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -890,8 +890,19 @@ static int pcie_init_slot(struct controller *ctrl)
>   static void pcie_cleanup_slot(struct controller *ctrl)
>   {
>   	struct slot *slot = ctrl->slot;
> -	cancel_delayed_work(&slot->work);
> +
> +	/*
> +	 * Following workqueue flushing logic is to deal with the special call path:
> +	 * 1) pcie_isr() ->  pciehp_handle_xxx() ->
> +	 *    queue_interrupt_event(pciehp_wq_event)->queue_work(pciehp_wq)
> +	 * 2) interrupt_event_handler() ->  handle_button_press_event() ->
> +	 *    queue_delayed_work(pciehp_wq)
> +	 * 3) pciehp_queue_pushbutton_work() ->  queue_work(pciehp_wq)
> +	 */
>   	flush_workqueue(pciehp_wq);
> +	cancel_delayed_work_sync(&slot->work);
> +	flush_workqueue(pciehp_wq);
> +
>   	kfree(slot);
>   }
> 

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