Re: [PATCH net-next v2 0/2] ptp: safely cleanup when unregistering a PTP clock

[Richard Cochran <richardcochran@gmail.com>]

On Tue, Sep 16, 2025 at 10:35:30PM +0100, Russell King (Oracle) wrote:
> (I'm assuming drivers/ptp/ patches go via net-next as there is no
> git tree against the "PTP HARDWARE CLOCK SUPPORT" maintainers entry.)
> 
> The standard rule in the kernel for unregistering user visible devices
> is to unpublish the userspace API before doing any shutdown of the
> resources necessary for the operation of the device.
> 
> PTP has several issues in this area:
> 
> 1. ptp_clock_unregister() cancells and destroys work while the PTP
>    chardev is still published, which gives the opportunity for a
>    precisely timed user API call to cause a driver to attempt to
>    queue the aux work.
> 
> 2. PTP pins are not cleaned up - if userspace has enabled PTP pins,
>    e.g. for extts, drivers are forced to do cleanup before calling
>    ptp_clock_unregister() to stop events being forwarded into the
>    PTP layer. E.g mv88e6xxx cancells its internal tai_event_work
>    to avoid calling into the PTP clock code with a stale ptp_clock
>    pointer, but a badly timed userspace EXTTS enable will re-schedule
>    the tai_event_work.

Thanks, Russell!

For the series:

Acked-by: Richard Cochran <richardcochran@gmail.com>