netdev - Re: [Intel-wired-lan] [PATCH v10 iwl-next 09/11] idpf: add Tx timestamp capabilities negotiation

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Message-ID: <757ed954-47a9-4be3-909e-5a343f453314@intel.com>
Date: Tue, 8 Apr 2025 14:23:20 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Milena Olech <milena.olech@...el.com>, <intel-wired-lan@...ts.osuosl.org>
CC: <netdev@...r.kernel.org>, <anthony.l.nguyen@...el.com>,
	<przemyslaw.kitszel@...el.com>, Alexander Lobakin
	<aleksander.lobakin@...el.com>, Emil Tantilov <emil.s.tantilov@...el.com>,
	Pavan Kumar Linga <pavan.kumar.linga@...el.com>, Samuel Salin
	<Samuel.salin@...el.com>
Subject: Re: [Intel-wired-lan] [PATCH v10 iwl-next 09/11] idpf: add Tx
 timestamp capabilities negotiation



On 4/8/2025 3:31 AM, Milena Olech wrote:
> +static void idpf_ptp_release_vport_tstamp(struct idpf_vport *vport)
> +{
> +	struct idpf_ptp_tx_tstamp *ptp_tx_tstamp, *tmp;
> +	struct list_head *head;
> +
> +	/* Remove list with free latches */
> +	spin_lock(&vport->tx_tstamp_caps->lock_free);
> +
> +	head = &vport->tx_tstamp_caps->latches_free;
> +	list_for_each_entry_safe(ptp_tx_tstamp, tmp, head, list_member) {
> +		list_del(&ptp_tx_tstamp->list_member);
> +		kfree(ptp_tx_tstamp);
> +	}
> +
> +	spin_unlock(&vport->tx_tstamp_caps->lock_free);
> +
> +	/* Remove list with latches in use */
> +	spin_lock(&vport->tx_tstamp_caps->lock_in_use);
> +
> +	head = &vport->tx_tstamp_caps->latches_in_use;
> +	list_for_each_entry_safe(ptp_tx_tstamp, tmp, head, list_member) {
> +		list_del(&ptp_tx_tstamp->list_member);
> +		kfree(ptp_tx_tstamp);
> +	}
> +
> +	spin_unlock(&vport->tx_tstamp_caps->lock_in_use);
> +
> +	kfree(vport->tx_tstamp_caps);
> +	vport->tx_tstamp_caps = NULL;
> +}
Could you provide a summary and overview of the locking scheme used
here? I see you have multiple spin locks for both the free bits and the
in-use bits, and its a bit hard to grasp the reasoning behind this. We
had a lot of issues getting locking for Tx timestamps correct in ice,
though most of that had to do with quirks in the hardware.

Thanks,
Jake