Re: [Intel-wired-lan] [PATCH] igb: Avoid starting unnecessary workqueues

From: Tony Nguyen <anthony.l.nguyen@intel.com>
To: Alessio Igor Bogani <alessio.bogani@elettra.eu>,
	<intel-wired-lan@lists.osuosl.org>
Subject: Re: [Intel-wired-lan] [PATCH] igb: Avoid starting unnecessary workqueues
Date: Fri, 21 Jul 2023 10:15:20 -0700	[thread overview]
Message-ID: <a4a27096-d231-631c-141f-6aee3b660cdc@intel.com> (raw)
In-Reply-To: <20230720145029.19674-1-alessio.bogani@elettra.eu>

On 7/20/2023 7:50 AM, Alessio Igor Bogani wrote:

Please designate a tree for your patch (net or net-next). As you have a 
Fixes, I assume it's net, but please be explicit.

> if ptp_clock_register() fails or CONFIG_PTP isn't enabled avoid starting PTP related workqueues.
> 
> In this way we can fix this:
>   BUG: unable to handle page fault for address: ffffc9000440b6f8
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 100000067 P4D 100000067 PUD 1001e0067 PMD 107dc5067 PTE 0
>   Oops: 0000 [#1] PREEMPT SMP
>   [...]
>   Workqueue: events igb_ptp_overflow_check
>   RIP: 0010:igb_rd32+0x1f/0x60
>   [...]
>   Call Trace:
>    igb_ptp_read_82580+0x20/0x50
>    timecounter_read+0x15/0x60
>    igb_ptp_overflow_check+0x1a/0x50
>    process_one_work+0x1cb/0x3c0
>    worker_thread+0x53/0x3f0
>    ? rescuer_thread+0x370/0x370
>    kthread+0x142/0x160
>    ? kthread_associate_blkcg+0xc0/0xc0
>    ret_from_fork+0x1f/0x30
> 
> Fixes: 1f6e8178d685 ("igb: Prevent dropped Tx timestamps via work items and interrupts.")
> Fixes: d339b1331616 ("igb: add PTP Hardware Clock code")
> Signed-off-by: Alessio Igor Bogani <alessio.bogani@elettra.eu>
> ---
>   drivers/net/ethernet/intel/igb/igb_ptp.c | 24 ++++++++++++------------
>   1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
> index 6f471b91f562..8165232052c8 100644
> --- a/drivers/net/ethernet/intel/igb/igb_ptp.c
> +++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
> @@ -1390,18 +1390,6 @@ void igb_ptp_init(struct igb_adapter *adapter)
>   		return;
>   	}
>   
> -	spin_lock_init(&adapter->tmreg_lock);
> -	INIT_WORK(&adapter->ptp_tx_work, igb_ptp_tx_work);
> -
> -	if (adapter->ptp_flags & IGB_PTP_OVERFLOW_CHECK)
> -		INIT_DELAYED_WORK(&adapter->ptp_overflow_work,
> -				  igb_ptp_overflow_check);
> -
> -	adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
> -	adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
> -
> -	igb_ptp_reset(adapter);
> -
>   	adapter->ptp_clock = ptp_clock_register(&adapter->ptp_caps,
>   						&adapter->pdev->dev);
>   	if (IS_ERR(adapter->ptp_clock)) {
> @@ -1411,6 +1399,18 @@ void igb_ptp_init(struct igb_adapter *adapter)
>   		dev_info(&adapter->pdev->dev, "added PHC on %s\n",
>   			 adapter->netdev->name);
>   		adapter->ptp_flags |= IGB_PTP_ENABLED;
> +
> +		spin_lock_init(&adapter->tmreg_lock);
> +		INIT_WORK(&adapter->ptp_tx_work, igb_ptp_tx_work);
> +
> +		if (adapter->ptp_flags & IGB_PTP_OVERFLOW_CHECK)
> +			INIT_DELAYED_WORK(&adapter->ptp_overflow_work,
> +					  igb_ptp_overflow_check);
> +
> +		adapter->tstamp_config.rx_filter = HWTSTAMP_FILTER_NONE;
> +		adapter->tstamp_config.tx_type = HWTSTAMP_TX_OFF;
> +
> +		igb_ptp_reset(adapter);

This concerns me that the PTP clock will be registered before 
initialization is complete/ready. I would prefer to see cleanup being 
done for the error case; have everything setup for the register, but 
remove the workqueues if we failed.

>   	}
>   }
>   
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