reset: protect struct reset_controller_dev with its own mutex

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>

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index e6c12fbebca985bdc3e1d1e44d8bca9718de8e83..acd9d10b1ceb64f5eab5373fa3873bf0dc1c5079 100644 (file)
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -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);
-
-       list_del(&rcdev->list);
+       scoped_guard(mutex, &reset_list_mutex)
+               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);

diff --git a/include/linux/reset-controller.h b/include/linux/reset-controller.h
index aa95b460fdf86f10002a465e285cd0119da6eeaf..185d2a9bd7cd381ddc51c0f1643c4e3cb196015e 100644 (file)
--- a/include/linux/reset-controller.h
+++ b/include/linux/reset-controller.h
@@ -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)