Re: [PATCH v2 0/8] HID: iio: Avoid race between callback setup and device exposure

[Andy Shevchenko]

On Wed, Jun 24, 2026 at 07:13:12AM +0530, Sanjay Chitroda wrote:
> On 23 June 2026 4:00:27 pm IST, Andy Shevchenko <andriy.shevchenko@xxxxxxxxx> wrote:
> >On Mon, Jun 22, 2026 at 10:59:56AM +0530, Sanjay Chitroda wrote:
> >> 
> >> This series avoid a race condition in HID IIO drivers related to the
> >> ordering between callback registration and device exposure.
> >> 
> >> Currently, several HID IIO drivers register the IIO device (making it
> >> visible to userspace and other kernel consumers) before all required
> >> callbacks and resources are fully initialized, or rely on devm-based
> >> cleanup in a way that does not guarantee correct teardown ordering.
> >> This creates a window where the device can be accessed while it is
> >
> >There is a difference between "this creates" and "this might create".
> >I believe Srinivas and others were asking for the proof. So, what path
> >in the code makes this happen or possible to happen?
> >
> iio_device_register() exposes the IIO device to user space, while
> sensor_hub_register_callback() registers callbacks for buffered IIO(streaming
> mode).
> 
> This might create window where from userspace buffer mode is enabled and
> callbacks are not registered which would result into loss of samples until
> callback registration completes, although no explicit failure. In teardown
> path which can resulting in stale/no data.
> 
> This was discussed in the v1 thread and v2 was posted based on discussion and
> agreement:
>  https://lore.kernel.org/all/3FED088A-651B-4E8B-840B-1B92CB4DF6F4@xxxxxxxxx/
> 
> >> not fully initialized or is being torn down, potentially leading to
> >> sample drop or stale/no data.
> >> 
> >> To handle this, the series ensures that:
> >>   - All required callbacks and resources are set up before the device
> >>     is registered with the IIO core
> >>   - Resource cleanup is performed explicitly where ordering matters
> >> 
> >> PS: This is prepratory series to convert all HID IIO driver to devm.
> >> 
> >> Testing:
> >>   - Compiled with W=1 for each patch in series
> >> 
> >> ---
> >> Changes in v2:
> >> - Drop fixes tag and rectify commit message with reference to that
> >
> >You also dropped my tag. Why?
> >
> Thank you for the review and tag on v1.
> 
> While code changes are intact in v2, the rational and commit message were
> updated substantially. Since commit message is as important as change which
> will be permanent in history for future reference, I chose to drop the tag to
> request a fresh review.

Now it's clear, thanks.
This version with changed commit messages seems good to me.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>

> I shall highlight the same in change log. I'll make sure to note in future revision.

Yes, please.

> 
> >> - Link to v1: https://patch.msgid.link/20260606-5-june-hid-iio-race-fixes-v1-0-27a848c5758f@xxxxxxxxx

-- 
With Best Regards,
Andy Shevchenko