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authorJean Delvare <khali@linux-fr.org>2012-09-10 10:14:02 +0200
committerJean Delvare <khali@endymion.delvare>2012-09-10 10:14:02 +0200
commit390946b17260797635cd9e65496b5a17b2db0a5d (patch)
tree42c4f0a172149d7e6752ddf55284cb1fcb386eec /drivers/i2c
parente68bb91baa0bb9817567bd45d560919e8e26373b (diff)
downloadlinux-linaro-stable-390946b17260797635cd9e65496b5a17b2db0a5d.tar.gz
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 <khali@linux-fr.org> Cc: Michael Lawnick <ml.lawnick@gmx.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/i2c-core.c22
1 files 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
@@ -637,6 +637,22 @@ static void i2c_adapter_dev_release(struct device *dev)
}
/*
+ * 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 *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,