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@xxxxxxxxxxxx>
Cc: Michael Lawnick <ml.lawnick@xxxxxx>
---
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
--
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