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

[Jacob Keller]

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