linux-kernel - Re: [PATCH V2 net-next 08/12] net: hns3: stop schedule reset service while unloading driver

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Date:   Wed, 24 Apr 2019 09:55:24 -0400
From:   Neil Horman <nhorman@...hat.com>
To:     Huazhong Tan <tanhuazhong@...wei.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, salil.mehta@...wei.com,
        yisen.zhuang@...wei.com, linuxarm@...wei.com,
        Peng Li <lipeng321@...wei.com>
Subject: Re: [PATCH V2 net-next 08/12] net: hns3: stop schedule reset service
 while unloading driver

On Wed, Apr 24, 2019 at 07:05:27PM +0800, Huazhong Tan wrote:
> This patch uses HCLGE_STATE_REMOVING/HCLGEVF_STATE_REMOVING flag to
> indicate that the driver is unloading, and we should stop new coming
> reset service to be scheduled, otherwise, reset service will access
> some resource which has been freed by unloading.
> 
> Signed-off-by: Huazhong Tan <tanhuazhong@...wei.com>
> Signed-off-by: Peng Li <lipeng321@...wei.com>
> ---
> V1->V2: fixes a flag setting error
> ---
>  drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c   | 4 +++-
>  drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c | 4 +++-
>  drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.h | 1 +
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c
> index 4d5568e..ead8308 100644
> --- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c
> +++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_main.c
> @@ -2175,7 +2175,8 @@ static void hclge_mbx_task_schedule(struct hclge_dev *hdev)
>  
>  static void hclge_reset_task_schedule(struct hclge_dev *hdev)
>  {
> -	if (!test_and_set_bit(HCLGE_STATE_RST_SERVICE_SCHED, &hdev->state))
> +	if (!test_bit(HCLGE_STATE_REMOVING, &hdev->state) &&
> +	    !test_and_set_bit(HCLGE_STATE_RST_SERVICE_SCHED, &hdev->state))
>  		schedule_work(&hdev->rst_service_task);
>  }
>  

In what use case do you need an extra bit for this?  From my read, this work
task only gets scheduled from:
1) Interrupt handlers
2) Its own service task

Based on the fact that you are calling cancel_work_sync(...rst_service_task)
from the pci teardown routine, irqs should all be disabled on your devices
already (meaning interrupts shouldn't schedule it), and cancel_work_sync
guarantees that rearming cant happen from within its own service task.

Neil