linux-kernel - [PATCH 1/3] i2c: atr: Fix lockdep for nested ATRs

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Message-ID: <20250203121629.2027871-2-demonsingur@gmail.com>
Date: Mon,  3 Feb 2025 14:15:15 +0200
From: Cosmin Tanislav <demonsingur@...il.com>
To: 
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
Subject: [PATCH 1/3] i2c: atr: Fix lockdep for nested ATRs

From: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>

When we have an ATR, and another ATR as a subdevice of the first ATR,
we get lockdep warnings for the i2c_atr.lock and
i2c_atr_chan.orig_addrs_lock. This is because lockdep uses a static key
for the locks, and doesn't see the locks of the separate ATR instances
as separate.

Fix this by generating a dynamic lock key per lock instance.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
---
 drivers/i2c/i2c-atr.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index 1a6ff47b42002..39b3b95c6842a 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -68,11 +68,13 @@ struct i2c_atr_alias_pool {
  * @atr:             The parent I2C ATR
  * @chan_id:         The ID of this channel
  * @alias_pairs_lock: Mutex protecting @alias_pairs
+ * @alias_pairs_lock_key: Lock key for @alias_pairs_lock
  * @alias_pairs:     List of @struct i2c_atr_alias_pair containing the
  *                   assigned aliases
  * @alias_pool:      Pool of available client aliases
  *
  * @orig_addrs_lock: Mutex protecting @orig_addrs
+ * @orig_addrs_lock_key: Lock key for @orig_addrs_lock
  * @orig_addrs:      Buffer used to store the original addresses during transmit
  * @orig_addrs_size: Size of @orig_addrs
  */
@@ -83,11 +85,13 @@ struct i2c_atr_chan {
 
 	/* Lock alias_pairs during attach/detach */
 	struct mutex alias_pairs_lock;
+	struct lock_class_key alias_pairs_lock_key;
 	struct list_head alias_pairs;
 	struct i2c_atr_alias_pool *alias_pool;
 
 	/* Lock orig_addrs during xfer */
 	struct mutex orig_addrs_lock;
+	struct lock_class_key orig_addrs_lock_key;
 	u16 *orig_addrs;
 	unsigned int orig_addrs_size;
 };
@@ -100,6 +104,7 @@ struct i2c_atr_chan {
  * @priv:      Private driver data, set with i2c_atr_set_driver_data()
  * @algo:      The &struct i2c_algorithm for adapters
  * @lock:      Lock for the I2C bus segment (see &struct i2c_lock_operations)
+ * @lock_key:  Lock key for @lock
  * @max_adapters: Maximum number of adapters this I2C ATR can have
  * @alias_pool: Optional common pool of available client aliases
  * @i2c_nb:    Notifier for remote client add & del events
@@ -115,6 +120,7 @@ struct i2c_atr {
 	struct i2c_algorithm algo;
 	/* lock for the I2C bus segment (see struct i2c_lock_operations) */
 	struct mutex lock;
+	struct lock_class_key lock_key;
 	int max_adapters;
 
 	struct i2c_atr_alias_pool *alias_pool;
@@ -679,7 +685,8 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
 	if (!atr)
 		return ERR_PTR(-ENOMEM);
 
-	mutex_init(&atr->lock);
+	lockdep_register_key(&atr->lock_key);
+	mutex_init_with_key(&atr->lock, &atr->lock_key);
 
 	atr->parent = parent;
 	atr->dev = dev;
@@ -707,6 +714,7 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
 	i2c_atr_free_alias_pool(atr->alias_pool);
 err_destroy_mutex:
 	mutex_destroy(&atr->lock);
+	lockdep_unregister_key(&atr->lock_key);
 	kfree(atr);
 
 	return ERR_PTR(ret);
@@ -723,6 +731,7 @@ void i2c_atr_delete(struct i2c_atr *atr)
 	bus_unregister_notifier(&i2c_bus_type, &atr->i2c_nb);
 	i2c_atr_free_alias_pool(atr->alias_pool);
 	mutex_destroy(&atr->lock);
+	lockdep_unregister_key(&atr->lock_key);
 	kfree(atr);
 }
 EXPORT_SYMBOL_NS_GPL(i2c_atr_delete, "I2C_ATR");
@@ -757,8 +766,10 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
 	chan->atr = atr;
 	chan->chan_id = chan_id;
 	INIT_LIST_HEAD(&chan->alias_pairs);
-	mutex_init(&chan->alias_pairs_lock);
-	mutex_init(&chan->orig_addrs_lock);
+	lockdep_register_key(&chan->alias_pairs_lock_key);
+	lockdep_register_key(&chan->orig_addrs_lock_key);
+	mutex_init_with_key(&chan->alias_pairs_lock, &chan->alias_pairs_lock_key);
+	mutex_init_with_key(&chan->orig_addrs_lock, &chan->orig_addrs_lock_key);
 
 	snprintf(chan->adap.name, sizeof(chan->adap.name), "i2c-%d-atr-%d",
 		 i2c_adapter_id(parent), chan_id);
@@ -835,6 +846,8 @@ int i2c_atr_add_adapter(struct i2c_atr *atr, struct i2c_atr_adap_desc *desc)
 	fwnode_handle_put(dev_fwnode(&chan->adap.dev));
 	mutex_destroy(&chan->orig_addrs_lock);
 	mutex_destroy(&chan->alias_pairs_lock);
+	lockdep_unregister_key(&chan->orig_addrs_lock_key);
+	lockdep_unregister_key(&chan->alias_pairs_lock_key);
 	kfree(chan);
 	return ret;
 }
@@ -872,6 +885,8 @@ void i2c_atr_del_adapter(struct i2c_atr *atr, u32 chan_id)
 	fwnode_handle_put(fwnode);
 	mutex_destroy(&chan->orig_addrs_lock);
 	mutex_destroy(&chan->alias_pairs_lock);
+	lockdep_unregister_key(&chan->orig_addrs_lock_key);
+	lockdep_unregister_key(&chan->alias_pairs_lock_key);
 	kfree(chan->orig_addrs);
 	kfree(chan);
 }
-- 
2.48.1