i2c: Limit core locking to the necessary sections
The i2c-core code tends to hold the core lock for longer than it
should. Limit locking to the necessary sections for both performance
and clarity. This is also a requirement to support I2C multiplexers in
the future.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Brownell <dbrownell@users.sourceforge.net>
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index b1fd00d..a2f1cd3 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -38,6 +38,9 @@
#include "i2c-core.h"
+/* core_lock protects i2c_adapter_idr, and guarantees
+ that device detection, deletion of detected devices, and attach_adapter
+ and detach_adapter calls are serialized */
static DEFINE_MUTEX(core_lock);
static DEFINE_IDR(i2c_adapter_idr);
@@ -418,13 +421,13 @@
int res = 0, dummy;
/* Can't register until after driver model init */
- if (unlikely(WARN_ON(!i2c_bus_type.p)))
- return -EAGAIN;
+ if (unlikely(WARN_ON(!i2c_bus_type.p))) {
+ res = -EAGAIN;
+ goto out_list;
+ }
mutex_init(&adap->bus_lock);
- mutex_lock(&core_lock);
-
/* Set default timeout to 1 second if not already set */
if (adap->timeout == 0)
adap->timeout = HZ;
@@ -443,16 +446,18 @@
i2c_scan_static_board_info(adap);
/* Notify drivers */
+ mutex_lock(&core_lock);
dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
i2c_do_add_adapter);
-
-out_unlock:
mutex_unlock(&core_lock);
- return res;
+
+ return 0;
out_list:
+ mutex_lock(&core_lock);
idr_remove(&i2c_adapter_idr, adap->nr);
- goto out_unlock;
+ mutex_unlock(&core_lock);
+ return res;
}
/**
@@ -590,22 +595,25 @@
int i2c_del_adapter(struct i2c_adapter *adap)
{
int res = 0;
-
- mutex_lock(&core_lock);
+ struct i2c_adapter *found;
/* First make sure that this adapter was ever added */
- if (idr_find(&i2c_adapter_idr, adap->nr) != adap) {
+ mutex_lock(&core_lock);
+ found = idr_find(&i2c_adapter_idr, adap->nr);
+ mutex_unlock(&core_lock);
+ if (found != adap) {
pr_debug("i2c-core: attempting to delete unregistered "
"adapter [%s]\n", adap->name);
- res = -EINVAL;
- goto out_unlock;
+ return -EINVAL;
}
/* Tell drivers about this removal */
+ mutex_lock(&core_lock);
res = bus_for_each_drv(&i2c_bus_type, NULL, adap,
i2c_do_del_adapter);
+ mutex_unlock(&core_lock);
if (res)
- goto out_unlock;
+ return res;
/* Detach any active clients. This can't fail, thus we do not
checking the returned value. */
@@ -619,7 +627,9 @@
wait_for_completion(&adap->dev_released);
/* free bus id */
+ mutex_lock(&core_lock);
idr_remove(&i2c_adapter_idr, adap->nr);
+ mutex_unlock(&core_lock);
dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);
@@ -627,9 +637,7 @@
added again */
memset(&adap->dev, 0, sizeof(adap->dev));
- out_unlock:
- mutex_unlock(&core_lock);
- return res;
+ return 0;
}
EXPORT_SYMBOL(i2c_del_adapter);
@@ -674,16 +682,15 @@
if (res)
return res;
- mutex_lock(&core_lock);
-
pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);
INIT_LIST_HEAD(&driver->clients);
/* Walk the adapters that are already present */
+ mutex_lock(&core_lock);
class_for_each_device(&i2c_adapter_class, NULL, driver,
__attach_adapter);
-
mutex_unlock(&core_lock);
+
return 0;
}
EXPORT_SYMBOL(i2c_register_driver);
@@ -721,14 +728,12 @@
void i2c_del_driver(struct i2c_driver *driver)
{
mutex_lock(&core_lock);
-
class_for_each_device(&i2c_adapter_class, NULL, driver,
__detach_adapter);
+ mutex_unlock(&core_lock);
driver_unregister(&driver->driver);
pr_debug("i2c-core: driver [%s] unregistered\n", driver->driver.name);
-
- mutex_unlock(&core_lock);
}
EXPORT_SYMBOL(i2c_del_driver);