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Commit 35fc37f8 authored by Jean Delvare's avatar Jean Delvare
Browse files

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: default avatarJean Delvare <khali@linux-fr.org>
Tested-by: default avatarRodolfo Giometti <giometti@linux.it>
Cc: David Brownell <dbrownell@users.sourceforge.net>
parent e549c2b5

drivers/i2c/i2c-core.c

+28 −23
Original line number Diff line number Diff line
@@ -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 @@ static int i2c_register_adapter(struct i2c_adapter *adap) 
	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 @@ static int i2c_register_adapter(struct i2c_adapter *adap) 
		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 @@ static int __unregister_client(struct device *dev, void *dummy) 
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 @@ int i2c_del_adapter(struct i2c_adapter *adap) 
	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 @@ int i2c_del_adapter(struct i2c_adapter *adap) 
	   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 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver) 
	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 @@ static int __detach_adapter(struct device *dev, void *data) 
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);