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

[Guenter Roeck <linux@roeck-us.net>]

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@roeck-us.net> 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@roeck-us.net>
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@roeck-us.net>
---
 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
-- 
2.45.2

---
From bf0a3d1a69d123eee3126f6a360f0ee3e54f7b17 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@roeck-us.net>
Date: Wed, 13 May 2026 09:25:46 -0700
Subject: [PATCH] hwmon: (corsair-psu) Protect debugfs accesses with subsystem
 lock

Debugfs accesses need to be mutext protected. Acquire hwmon
subsystem lock to avoid race conditions against hwmon sysfs
accesses.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/corsair-psu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
index 76f3e1da68d0..4a456ba44a9b 100644
--- a/drivers/hwmon/corsair-psu.c
+++ b/drivers/hwmon/corsair-psu.c
@@ -664,6 +664,8 @@ static void print_uptime(struct seq_file *seqf, u8 cmd)
 	long val;
 	int ret;
 
+	guard(hwmon_lock)(priv->hwmon_dev);
+
 	ret = corsairpsu_get_value(priv, cmd, 0, &val);
 	if (ret < 0) {
 		seq_puts(seqf, "N/A\n");
@@ -723,6 +725,8 @@ static int ocpmode_show(struct seq_file *seqf, void *unused)
 	long val;
 	int ret;
 
+	guard(hwmon_lock)(priv->hwmon_dev);
+
 	/*
 	 * The rail mode is switchable on the fly. The RAW interface can be used for this. But it
 	 * will not be included here, because I consider it somewhat dangerous for the health of the
-- 
2.45.2