Re: [PATCH] hwmon: corsair-psu: fix and readd locking of command buffer

[Guenter Roeck]

On 5/13/26 10:50, Wilken Gottwalt wrote:
> On Wed, 13 May 2026 09:42:08 -0700
> Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> > On Wed, May 13, 2026 at 03:53:51PM +0000, Wilken Gottwalt wrote:
> > > On Wed, 13 May 2026 07:58:14 -0700
> > > Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > ...
> > > Okay, that will get a bit complex now, because I added my hack and I see
> > > exactly what I assumed is happening.
> > ...
> > > If this does not explain the obvious issue, I have not idea how explain
> > > it further. My English is limited. This is a HID driver with data gathering
> > > functions running in the context of the USB-HID context. Callbacks from the
> > > hwmon and the debugfs subsystem call these data gathering functions, and the
> > > first function in that context, corsairpsu_request(), which can run several
> > > instances in paralellel, needs the mutex.
> >
> > You don't explain why the patches below are insufficient.
> >
> > I used guard() to keep the changes simple, but hwmon_lock() / hwmon_unlock()
> > would be similar. Please provide evidence that this does not work.
> >
> > Thanks,
> > Guenter
> > --
> >  From aa3ec1484bdd619e8fa2ce569ec653d35fbf3615 Mon Sep 17 00:00:00 2001
> > From: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Date: Wed, 13 May 2026 07:14:33 -0700
> > Subject: [PATCH 1/4] hwmon: Support guard() and scoped_guard for subsystem
> >   locks
> >
> > Add support for guard() and scoped_guard() for the hwmon subsystem lock
> > to simplify its use.
> >
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> >   Documentation/hwmon/hwmon-kernel-api.rst | 7 ++++---
> >   include/linux/hwmon.h                    | 2 ++
> >   2 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/hwmon/hwmon-kernel-api.rst b/Documentation/hwmon/hwmon-kernel-api.rst
> > index 1d7f1397a827..9fcde32a140d 100644
> > --- a/Documentation/hwmon/hwmon-kernel-api.rst
> > +++ b/Documentation/hwmon/hwmon-kernel-api.rst
> > @@ -85,9 +85,10 @@ removal.
> >   When using ``[devm_]hwmon_device_register_with_info()`` to register the
> >   hardware monitoring device, accesses using the associated access functions
> >   are serialised by the hardware monitoring core. If a driver needs locking
> > -for other functions such as interrupt handlers or for attributes which are
> > -fully implemented in the driver, hwmon_lock() and hwmon_unlock() can be used
> > -to ensure that calls to those functions are serialized.
> > +for other functions such as interrupt handlers, attributes which are fully
> > +implemented in the driver, or debugfs functions, hwmon_lock() and hwmon_unlock()
> > +can be used to ensure that calls to those functions are serialized. Those
> > +functions also support guard() and scoped_guard() variants.
> >   
> >   Using devm_hwmon_device_register_with_info()
> >   --------------------------------------------
> > diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h
> > index 301a83afbd66..04959e044fd0 100644
> > --- a/include/linux/hwmon.h
> > +++ b/include/linux/hwmon.h
> > @@ -495,6 +495,8 @@ char *devm_hwmon_sanitize_name(struct device *dev, const char *name);
> >   void hwmon_lock(struct device *dev);
> >   void hwmon_unlock(struct device *dev);
> >   
> > +DEFINE_GUARD(hwmon_lock, struct device *, hwmon_lock(_T), hwmon_unlock(_T))
> > +
> >   /**
> >    * hwmon_is_bad_char - Is the char invalid in a hwmon name
> >    * @ch: the char to be considered
>
> Now I am completely confused. What is that guard() and scoped_guard() patch?

Why do you think I attached it ? Why would I do that if it was already upstream ?
I wrote it this morning, that is why. You'd find it on the mailing list if
you looked.

Ok, fine, I'll send another patch without it if you don't want to apply it
even for testing.

Guenter