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reset: protect struct reset_controller_dev with its own mutex

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Currently we use a single, global mutex - misleadingly names
reset_list_mutex - to protect the global list of reset devices,
per-controller list of reset control handles and also internal fields of
struct reset_control. Locking can be made a lot more fine-grained if we
use a separate mutex for serializing operations on the list AND
accessing the reset controller device.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
This commit is contained in:
Bartosz Golaszewski 2026-03-06 18:22:53 +01:00 committed by Philipp Zabel
parent 78ebbff6d1
commit 44a0acb2ca
2 changed files with 30 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
drivers/reset/core.c
View File

@ -131,6 +131,7 @@ int reset_controller_register(struct reset_controller_dev *rcdev)
}
INIT_LIST_HEAD(&rcdev->reset_control_head);
mutex_init(&rcdev->lock);
guard(mutex)(&reset_list_mutex);
@ -143,6 +144,8 @@ EXPORT_SYMBOL_GPL(reset_controller_register);
static void reset_controller_remove(struct reset_controller_dev *rcdev,
struct reset_control *rstc)
{
lockdep_assert_held(&rcdev->lock);
list_del(&rstc->list);
module_put(rcdev->owner);
put_device(rcdev->dev);
@ -156,19 +159,22 @@ void reset_controller_unregister(struct reset_controller_dev *rcdev)
{
struct reset_control *rstc, *pos;
guard(mutex)(&reset_list_mutex);
scoped_guard(mutex, &reset_list_mutex)
list_del(&rcdev->list);
list_del(&rcdev->list);
/*
* Numb but don't free the remaining reset control handles that are
* still held by consumers.
*/
list_for_each_entry_safe(rstc, pos, &rcdev->reset_control_head, list) {
rcu_assign_pointer(rstc->rcdev, NULL);
synchronize_srcu(&rstc->srcu);
reset_controller_remove(rcdev, rstc);
scoped_guard(mutex, &rcdev->lock) {
/*
* Numb but don't free the remaining reset control handles that are
* still held by consumers.
*/
list_for_each_entry_safe(rstc, pos, &rcdev->reset_control_head, list) {
rcu_assign_pointer(rstc->rcdev, NULL);
synchronize_srcu(&rstc->srcu);
reset_controller_remove(rcdev, rstc);
}
}
mutex_destroy(&rcdev->lock);
}
EXPORT_SYMBOL_GPL(reset_controller_unregister);
@ -712,10 +718,12 @@ int reset_control_acquire(struct reset_control *rstc)
if (!rcdev)
return -ENODEV;
list_for_each_entry(rc, &rcdev->reset_control_head, list) {
if (rstc != rc && rstc->id == rc->id) {
if (rc->acquired)
return -EBUSY;
scoped_guard(mutex, &rcdev->lock) {
list_for_each_entry(rc, &rcdev->reset_control_head, list) {
if (rstc != rc && rstc->id == rc->id) {
if (rc->acquired)
return -EBUSY;
}
}
}
@ -806,7 +814,7 @@ __reset_control_get_internal(struct reset_controller_dev *rcdev,
struct reset_control *rstc;
int ret;
lockdep_assert_held(&reset_list_mutex);
lockdep_assert_held(&rcdev->lock);
/* Expect callers to filter out OPTIONAL and DEASSERTED bits */
if (WARN_ON(flags & ~(RESET_CONTROL_FLAGS_BIT_SHARED |
@ -868,8 +876,10 @@ static void __reset_control_release(struct kref *kref)
scoped_guard(srcu, &rstc->srcu) {
rcdev = rcu_replace_pointer(rstc->rcdev, NULL, true);
if (rcdev)
if (rcdev) {
guard(mutex)(&rcdev->lock);
reset_controller_remove(rcdev, rstc);
}
}
synchronize_srcu(&rstc->srcu);

3
include/linux/reset-controller.h
View File

@ -3,6 +3,7 @@
#define _LINUX_RESET_CONTROLLER_H_
#include <linux/list.h>
#include <linux/mutex.h>
struct reset_controller_dev;
@ -40,6 +41,7 @@ struct of_phandle_args;
* device tree to id as given to the reset control ops, defaults
* to :c:func:`of_reset_simple_xlate`.
* @nr_resets: number of reset controls in this reset controller device
* @lock: protects the reset control list from concurrent access
*/
struct reset_controller_dev {
const struct reset_control_ops *ops;
@ -52,6 +54,7 @@ struct reset_controller_dev {
int (*of_xlate)(struct reset_controller_dev *rcdev,
const struct of_phandle_args *reset_spec);
unsigned int nr_resets;
struct mutex lock;
};
#if IS_ENABLED(CONFIG_RESET_CONTROLLER)