linux/drivers/base/dd.c
Alan Stern bf74ad5bc4 [PATCH] Hold the device's parent's lock during probe and remove
This patch (as604) makes the driver core hold a device's parent's lock
as well as the device's lock during calls to the probe and remove
methods in a driver.  This facility is needed by USB device drivers,
owing to the peculiar way USB devices work:

	A device provides multiple interfaces, and drivers are bound
	to interfaces rather than to devices;

	Nevertheless a reset, reset-configuration, suspend, or resume
	affects the entire device and requires the caller to hold the
	lock for the device, not just a lock for one of the interfaces.

Since a USB driver's probe method is always called with the interface
lock held, the locking order rules (always lock parent before child)
prevent these methods from acquiring the device lock.  The solution
provided here is to call all probe and remove methods, for all devices
(not just USB), with the parent lock already acquired.

Although currently only the USB subsystem requires these changes, people
have mentioned in prior discussion that the overhead of acquiring an
extra semaphore in all the prove/remove sequences is not overly large.

Up to now, the USB core has been using its own set of private
semaphores.  A followup patch will remove them, relying entirely on the
device semaphores provided by the driver core.

The code paths affected by this patch are:

	device_add and device_del: The USB core already holds the parent
	lock, so no actual change is needed.

	driver_register and driver_unregister: The driver core will now
	lock both the parent and the device before probing or removing.

	driver_bind and driver_unbind (in sysfs): These routines will
	now lock both the parent and the device before binding or
	unbinding.

	bus_rescan_devices: The helper routine will lock the parent
	before probing a device.

I have not tested this patch for conflicts with other subsystems.  As
far as I can see, the only possibility of conflict would lie in the
bus_rescan_devices pathway, and it seems pretty remote.  Nevertheless,
it would be good for this to get a lot of testing in -mm.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-01-04 16:18:08 -08:00

263 lines
6.6 KiB
C

/*
* drivers/base/dd.c - The core device/driver interactions.
*
* This file contains the (sometimes tricky) code that controls the
* interactions between devices and drivers, which primarily includes
* driver binding and unbinding.
*
* All of this code used to exist in drivers/base/bus.c, but was
* relocated to here in the name of compartmentalization (since it wasn't
* strictly code just for the 'struct bus_type'.
*
* Copyright (c) 2002-5 Patrick Mochel
* Copyright (c) 2002-3 Open Source Development Labs
*
* This file is released under the GPLv2
*/
#include <linux/device.h>
#include <linux/module.h>
#include "base.h"
#include "power/power.h"
#define to_drv(node) container_of(node, struct device_driver, kobj.entry)
/**
* device_bind_driver - bind a driver to one device.
* @dev: device.
*
* Allow manual attachment of a driver to a device.
* Caller must have already set @dev->driver.
*
* Note that this does not modify the bus reference count
* nor take the bus's rwsem. Please verify those are accounted
* for before calling this. (It is ok to call with no other effort
* from a driver's probe() method.)
*
* This function must be called with @dev->sem held.
*/
void device_bind_driver(struct device * dev)
{
if (klist_node_attached(&dev->knode_driver))
return;
pr_debug("bound device '%s' to driver '%s'\n",
dev->bus_id, dev->driver->name);
klist_add_tail(&dev->knode_driver, &dev->driver->klist_devices);
sysfs_create_link(&dev->driver->kobj, &dev->kobj,
kobject_name(&dev->kobj));
sysfs_create_link(&dev->kobj, &dev->driver->kobj, "driver");
}
/**
* driver_probe_device - attempt to bind device & driver.
* @drv: driver.
* @dev: device.
*
* First, we call the bus's match function, if one present, which
* should compare the device IDs the driver supports with the
* device IDs of the device. Note we don't do this ourselves
* because we don't know the format of the ID structures, nor what
* is to be considered a match and what is not.
*
* This function returns 1 if a match is found, an error if one
* occurs (that is not -ENODEV or -ENXIO), and 0 otherwise.
*
* This function must be called with @dev->sem held. When called
* for a USB interface, @dev->parent->sem must be held as well.
*/
int driver_probe_device(struct device_driver * drv, struct device * dev)
{
int ret = 0;
if (drv->bus->match && !drv->bus->match(dev, drv))
goto Done;
pr_debug("%s: Matched Device %s with Driver %s\n",
drv->bus->name, dev->bus_id, drv->name);
dev->driver = drv;
if (drv->probe) {
ret = drv->probe(dev);
if (ret) {
dev->driver = NULL;
goto ProbeFailed;
}
}
device_bind_driver(dev);
ret = 1;
pr_debug("%s: Bound Device %s to Driver %s\n",
drv->bus->name, dev->bus_id, drv->name);
goto Done;
ProbeFailed:
if (ret == -ENODEV || ret == -ENXIO) {
/* Driver matched, but didn't support device
* or device not found.
* Not an error; keep going.
*/
ret = 0;
} else {
/* driver matched but the probe failed */
printk(KERN_WARNING
"%s: probe of %s failed with error %d\n",
drv->name, dev->bus_id, ret);
}
Done:
return ret;
}
static int __device_attach(struct device_driver * drv, void * data)
{
struct device * dev = data;
return driver_probe_device(drv, dev);
}
/**
* device_attach - try to attach device to a driver.
* @dev: device.
*
* Walk the list of drivers that the bus has and call
* driver_probe_device() for each pair. If a compatible
* pair is found, break out and return.
*
* Returns 1 if the device was bound to a driver;
* 0 if no matching device was found; error code otherwise.
*
* When called for a USB interface, @dev->parent->sem must be held.
*/
int device_attach(struct device * dev)
{
int ret = 0;
down(&dev->sem);
if (dev->driver) {
device_bind_driver(dev);
ret = 1;
} else
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
up(&dev->sem);
return ret;
}
static int __driver_attach(struct device * dev, void * data)
{
struct device_driver * drv = data;
/*
* Lock device and try to bind to it. We drop the error
* here and always return 0, because we need to keep trying
* to bind to devices and some drivers will return an error
* simply if it didn't support the device.
*
* driver_probe_device() will spit a warning if there
* is an error.
*/
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
down(&dev->sem);
if (!dev->driver)
driver_probe_device(drv, dev);
up(&dev->sem);
if (dev->parent)
up(&dev->parent->sem);
return 0;
}
/**
* driver_attach - try to bind driver to devices.
* @drv: driver.
*
* Walk the list of devices that the bus has on it and try to
* match the driver with each one. If driver_probe_device()
* returns 0 and the @dev->driver is set, we've found a
* compatible pair.
*/
void driver_attach(struct device_driver * drv)
{
bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}
/**
* device_release_driver - manually detach device from driver.
* @dev: device.
*
* Manually detach device from driver.
*
* __device_release_driver() must be called with @dev->sem held.
* When called for a USB interface, @dev->parent->sem must be held
* as well.
*/
static void __device_release_driver(struct device * dev)
{
struct device_driver * drv;
drv = dev->driver;
if (drv) {
get_driver(drv);
sysfs_remove_link(&drv->kobj, kobject_name(&dev->kobj));
sysfs_remove_link(&dev->kobj, "driver");
klist_remove(&dev->knode_driver);
if (drv->remove)
drv->remove(dev);
dev->driver = NULL;
put_driver(drv);
}
}
void device_release_driver(struct device * dev)
{
/*
* If anyone calls device_release_driver() recursively from
* within their ->remove callback for the same device, they
* will deadlock right here.
*/
down(&dev->sem);
__device_release_driver(dev);
up(&dev->sem);
}
/**
* driver_detach - detach driver from all devices it controls.
* @drv: driver.
*/
void driver_detach(struct device_driver * drv)
{
struct device * dev;
for (;;) {
spin_lock(&drv->klist_devices.k_lock);
if (list_empty(&drv->klist_devices.k_list)) {
spin_unlock(&drv->klist_devices.k_lock);
break;
}
dev = list_entry(drv->klist_devices.k_list.prev,
struct device, knode_driver.n_node);
get_device(dev);
spin_unlock(&drv->klist_devices.k_lock);
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
down(&dev->sem);
if (dev->driver == drv)
__device_release_driver(dev);
up(&dev->sem);
if (dev->parent)
up(&dev->parent->sem);
put_device(dev);
}
}
EXPORT_SYMBOL_GPL(device_bind_driver);
EXPORT_SYMBOL_GPL(device_release_driver);
EXPORT_SYMBOL_GPL(device_attach);
EXPORT_SYMBOL_GPL(driver_attach);