netdev - Re: [Intel-wired-lan] [PATCH net] iavf: initialize waitqueues before starting watchdog

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Date: Thu, 19 Oct 2023 11:15:53 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Michal Schmidt <mschmidt@...hat.com>, <netdev@...r.kernel.org>
CC: Sudheer Mogilappagari <sudheer.mogilappagari@...el.com>,
	<intel-wired-lan@...ts.osuosl.org>, Tony Nguyen <anthony.l.nguyen@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>, Jesse Brandeburg
	<jesse.brandeburg@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH net] iavf: initialize waitqueues before
 starting watchdog_task

On 10/19/23 09:13, Michal Schmidt wrote:
> It is not safe to initialize the waitqueues after queueing the
> watchdog_task. It will be using them.
> 
> The chance of this causing a real problem is very small, because
> there will be some sleeping before any of the waitqueues get used.
> I got a crash only after inserting an artificial sleep in iavf_probe.
> 
> Queue the watchdog_task as the last step in iavf_probe. Add a comment to
> prevent repeating the mistake.
> 
> Fixes: fe2647ab0c99 ("i40evf: prevent VF close returning before state transitions to DOWN")
> Signed-off-by: Michal Schmidt <mschmidt@...hat.com>
> ---
>   drivers/net/ethernet/intel/iavf/iavf_main.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
> index 6a2e6d64bc3a..5b5c0525aa13 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> @@ -4982,8 +4982,6 @@ static int iavf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	INIT_WORK(&adapter->finish_config, iavf_finish_config);
>   	INIT_DELAYED_WORK(&adapter->watchdog_task, iavf_watchdog_task);
>   	INIT_DELAYED_WORK(&adapter->client_task, iavf_client_task);
> -	queue_delayed_work(adapter->wq, &adapter->watchdog_task,
> -			   msecs_to_jiffies(5 * (pdev->devfn & 0x07)));
>   
>   	/* Setup the wait queue for indicating transition to down status */
>   	init_waitqueue_head(&adapter->down_waitqueue);
> @@ -4994,6 +4992,9 @@ static int iavf_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	/* Setup the wait queue for indicating virtchannel events */
>   	init_waitqueue_head(&adapter->vc_waitqueue);
>   
> +	queue_delayed_work(adapter->wq, &adapter->watchdog_task,
> +			   msecs_to_jiffies(5 * (pdev->devfn & 0x07)));
> +	/* Initialization goes on in the work. Do not add more of it below. */
>   	return 0;
>   
>   err_ioremap:

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>