From 390946b17260797635cd9e65496b5a17b2db0a5d Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Mon, 10 Sep 2012 10:14:02 +0200 Subject: [PATCH] i2c-core: Fix for lockdep validator If kernel is compiled with CONFIG_PROVE_LOCKING the validator raises an error when a multiplexer is removed via sysfs and sub-clients are connected to it. This is a false positive. Documentation/lockdep-design.txt recommends to handle this via calls to mutex_lock_nested(). Based on an earlier fix from Michael Lawnick. Note that the extra code resolves to nothing unless CONFIG_DEBUG_LOCK_ALLOC=y. Signed-off-by: Jean Delvare Cc: Michael Lawnick --- drivers/i2c/i2c-core.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 2efa56c5ff2c..2091ae8f539a 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -636,6 +636,22 @@ static void i2c_adapter_dev_release(struct device *dev) complete(&adap->dev_released); } +/* + * This function is only needed for mutex_lock_nested, so it is never + * called unless locking correctness checking is enabled. Thus we + * make it inline to avoid a compiler warning. That's what gcc ends up + * doing anyway. + */ +static inline unsigned int i2c_adapter_depth(struct i2c_adapter *adapter) +{ + unsigned int depth = 0; + + while ((adapter = i2c_parent_is_i2c_adapter(adapter))) + depth++; + + return depth; +} + /* * Let users instantiate I2C devices through sysfs. This can be used when * platform initialization code doesn't contain the proper data for @@ -726,7 +742,8 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr, /* Make sure the device was added through sysfs */ res = -ENOENT; - mutex_lock(&adap->userspace_clients_lock); + mutex_lock_nested(&adap->userspace_clients_lock, + i2c_adapter_depth(adap)); list_for_each_entry_safe(client, next, &adap->userspace_clients, detected) { if (client->addr == addr) { @@ -1073,7 +1090,8 @@ int i2c_del_adapter(struct i2c_adapter *adap) return res; /* Remove devices instantiated from sysfs */ - mutex_lock(&adap->userspace_clients_lock); + mutex_lock_nested(&adap->userspace_clients_lock, + i2c_adapter_depth(adap)); list_for_each_entry_safe(client, next, &adap->userspace_clients, detected) { dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name, -- GitLab