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 <[email protected]> Cc: Michael Lawnick <[email protected]> --- Changes since v2: * Inline function i2c_adapter_depth to avoid a compiler warning. * Document the reason why it it implemented that way. drivers/i2c/i2c-core.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) --- linux-3.6-rc4.orig/drivers/i2c/i2c-core.c 2012-09-07 17:53:31.000000000 +0200 +++ linux-3.6-rc4/drivers/i2c/i2c-core.c 2012-09-08 09:36:13.538537033 +0200 @@ -637,6 +637,22 @@ static void i2c_adapter_dev_release(stru } /* + * 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 * whatever reason. Also useful for drivers that do device detection and @@ -726,7 +742,8 @@ i2c_sysfs_delete_device(struct device *d /* 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 * 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, -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
