Re: [PATCH v2 08/14] reset: handle removing supplier before consumers

[Philipp Zabel]

Hi Bartosz,

On Mo, 2026-02-23 at 11:06 +0100, Bartosz Golaszewski wrote:
> Except for the reset-gpio, all reset drivers use device tree - and as
> such - benefit from the device links set up by driver core. This means,
> that no reset supplier will be unbound before all its consumers have
> been. For this reason, nobody bothered making the reset core resiliant
> to the object life-time issues that are plagueing the kernel. In this
> case: reset control handles referencing the reset provider device with
> no serialization or NULL-pointer checking.
> 
> We now want to make the reset core fwnode-agnostic but before we do, we
> must make sure it can survive unbinding of suppliers with consumers
> still holding reset control handles.
> 
> To that end: use SRCU to protect the rcdev pointer inside struct
> reset_control. We protect all sections using the pointer with SRCU
> read-only critical sections and synchronize SRCU after every
> modification of the pointer.
> 
> This is in line with what the GPIO subsystem does and what the proposed
> revocable API tries to generalize. When and if the latter makes its way
> into the kernel, reset core could potentially also be generalized to use
> it.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>

The changes look fine to me, but is there some kind of consensus that
SRCU is the right tool for this kind of protection? Is there a reason
to use SRCU over rw_semaphore here, apart from similarity to the
implementation in the GPIO subsystem?

regards
Philipp