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Commit af70316a authored by Patrick Mochel's avatar Patrick Mochel Committed by Greg Kroah-Hartman
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[PATCH] Add a semaphore to struct device to synchronize calls to its driver. 



This adds a per-device semaphore that is taken before every call from the core to a
driver method. This prevents e.g. simultaneous calls to the ->suspend() or ->resume()
and ->probe() or ->release(), potentially saving a whole lot of headaches.

It also moves us a step closer to removing the bus rwsem, since it protects the fields
in struct device that are modified by the core.

Signed-off-by: default avatarPatrick Mochel <mochel@digitalimplant.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent eb51b650

drivers/base/bus.c

+11 −3
Original line number Diff line number Diff line
@@ -283,18 +283,22 @@ void device_bind_driver(struct device * dev) 
 */

int driver_probe_device(struct device_driver * drv, struct device * dev)

{

	int error = 0;



	if (drv->bus->match && !drv->bus->match(dev, drv))

		return -ENODEV;



	down(&dev->sem);

	dev->driver = drv;

	if (drv->probe) {

		int error = drv->probe(dev);

		error = drv->probe(dev);

		if (error) {

			dev->driver = NULL;

			up(&dev->sem);

			return error;

		}

	}



	up(&dev->sem);

	device_bind_driver(dev);

	return 0;

}
@@ -385,7 +389,10 @@ void driver_attach(struct device_driver * drv) 


void device_release_driver(struct device * dev)

{

	struct device_driver * drv = dev->driver;

	struct device_driver * drv;



	down(&dev->sem);

	drv = dev->driver;

	if (drv) {

		sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));

		sysfs_remove_link(&dev->kobj, "driver");
@@ -394,6 +401,7 @@ void device_release_driver(struct device * dev) 
			drv->remove(dev);

		dev->driver = NULL;

	}

	up(&dev->sem);

}

drivers/base/core.c

+1 −0
Original line number Diff line number Diff line
@@ -212,6 +212,7 @@ void device_initialize(struct device *dev) 
	INIT_LIST_HEAD(&dev->driver_list);

	INIT_LIST_HEAD(&dev->bus_list);

	INIT_LIST_HEAD(&dev->dma_pools);

	init_MUTEX(&dev->sem);

}



/**

drivers/base/power/resume.c

+6 −2
Original line number Diff line number Diff line
@@ -22,6 +22,9 @@ extern int sysdev_resume(void); 


int resume_device(struct device * dev)

{

	int error = 0;



	down(&dev->sem);

	if (dev->power.pm_parent

			&& dev->power.pm_parent->power.power_state) {

		dev_err(dev, "PM: resume from %d, parent %s still %d\n",
@@ -31,9 +34,10 @@ int resume_device(struct device * dev) 
	}

	if (dev->bus && dev->bus->resume) {

		dev_dbg(dev,"resuming\n");

		return dev->bus->resume(dev);

		error = dev->bus->resume(dev);

	}

	return 0;

	up(&dev->sem);

	return error;

}

drivers/base/power/suspend.c

+2 −1
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ int suspend_device(struct device * dev, pm_message_t state) 
{

	int error = 0;



	down(&dev->sem);

	if (dev->power.power_state) {

		dev_dbg(dev, "PM: suspend %d-->%d\n",

			dev->power.power_state, state);
@@ -58,7 +59,7 @@ int suspend_device(struct device * dev, pm_message_t state) 
		dev_dbg(dev, "suspending\n");

		error = dev->bus->suspend(dev, state);

	}



	up(&dev->sem);

	return error;

}

include/linux/device.h

+4 −0
Original line number Diff line number Diff line
@@ -264,6 +264,10 @@ struct device { 
	struct kobject kobj;

	char	bus_id[BUS_ID_SIZE];	/* position on parent bus */



	struct semaphore	sem;	/* semaphore to synchronize calls to

					 * its driver.

					 */



	struct bus_type	* bus;		/* type of bus device is on */

	struct device_driver *driver;	/* which driver has allocated this

					   device */