linux/drivers/base/driver.c
James Bottomley 34bb61f9dd [PATCH] fix klist semantics for lists which have elements removed on traversal
The problem is that klists claim to provide semantics for safe traversal of
lists which are being modified.  The failure case is when traversal of a
list causes element removal (a fairly common case).  The issue is that
although the list node is refcounted, if it is embedded in an object (which
is universally the case), then the object will be freed regardless of the
klist refcount leading to slab corruption because the klist iterator refers
to the prior element to get the next.

The solution is to make the klist take and release references to the
embedding object meaning that the embedding object won't be released until
the list relinquishes the reference to it.

(akpm: fast-track this because it's needed for the 2.6.13 scsi merge)

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-07 18:26:54 -07:00

224 lines
5.5 KiB
C

/*
* driver.c - centralized device driver management
*
* Copyright (c) 2002-3 Patrick Mochel
* Copyright (c) 2002-3 Open Source Development Labs
*
* This file is released under the GPLv2
*
*/
#include <linux/config.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/string.h>
#include "base.h"
#define to_dev(node) container_of(node, struct device, driver_list)
#define to_drv(obj) container_of(obj, struct device_driver, kobj)
static struct device * next_device(struct klist_iter * i)
{
struct klist_node * n = klist_next(i);
return n ? container_of(n, struct device, knode_driver) : NULL;
}
/**
* driver_for_each_device - Iterator for devices bound to a driver.
* @drv: Driver we're iterating.
* @data: Data to pass to the callback.
* @fn: Function to call for each device.
*
* Iterate over the @drv's list of devices calling @fn for each one.
*/
int driver_for_each_device(struct device_driver * drv, struct device * start,
void * data, int (*fn)(struct device *, void *))
{
struct klist_iter i;
struct device * dev;
int error = 0;
if (!drv)
return -EINVAL;
klist_iter_init_node(&drv->klist_devices, &i,
start ? &start->knode_driver : NULL);
while ((dev = next_device(&i)) && !error)
error = fn(dev, data);
klist_iter_exit(&i);
return error;
}
EXPORT_SYMBOL_GPL(driver_for_each_device);
/**
* driver_find_device - device iterator for locating a particular device.
* @driver: The device's driver
* @start: Device to begin with
* @data: Data to pass to match function
* @match: Callback function to check device
*
* This is similar to the driver_for_each_device() function above, but
* it returns a reference to a device that is 'found' for later use, as
* determined by the @match callback.
*
* The callback should return 0 if the device doesn't match and non-zero
* if it does. If the callback returns non-zero, this function will
* return to the caller and not iterate over any more devices.
*/
struct device * driver_find_device(struct device_driver *drv,
struct device * start, void * data,
int (*match)(struct device *, void *))
{
struct klist_iter i;
struct device *dev;
if (!drv)
return NULL;
klist_iter_init_node(&drv->klist_devices, &i,
(start ? &start->knode_driver : NULL));
while ((dev = next_device(&i)))
if (match(dev, data) && get_device(dev))
break;
klist_iter_exit(&i);
return dev;
}
EXPORT_SYMBOL_GPL(driver_find_device);
/**
* driver_create_file - create sysfs file for driver.
* @drv: driver.
* @attr: driver attribute descriptor.
*/
int driver_create_file(struct device_driver * drv, struct driver_attribute * attr)
{
int error;
if (get_driver(drv)) {
error = sysfs_create_file(&drv->kobj, &attr->attr);
put_driver(drv);
} else
error = -EINVAL;
return error;
}
/**
* driver_remove_file - remove sysfs file for driver.
* @drv: driver.
* @attr: driver attribute descriptor.
*/
void driver_remove_file(struct device_driver * drv, struct driver_attribute * attr)
{
if (get_driver(drv)) {
sysfs_remove_file(&drv->kobj, &attr->attr);
put_driver(drv);
}
}
/**
* get_driver - increment driver reference count.
* @drv: driver.
*/
struct device_driver * get_driver(struct device_driver * drv)
{
return drv ? to_drv(kobject_get(&drv->kobj)) : NULL;
}
/**
* put_driver - decrement driver's refcount.
* @drv: driver.
*/
void put_driver(struct device_driver * drv)
{
kobject_put(&drv->kobj);
}
static void klist_devices_get(struct klist_node *n)
{
struct device *dev = container_of(n, struct device, knode_driver);
get_device(dev);
}
static void klist_devices_put(struct klist_node *n)
{
struct device *dev = container_of(n, struct device, knode_driver);
put_device(dev);
}
/**
* driver_register - register driver with bus
* @drv: driver to register
*
* We pass off most of the work to the bus_add_driver() call,
* since most of the things we have to do deal with the bus
* structures.
*
* The one interesting aspect is that we setup @drv->unloaded
* as a completion that gets complete when the driver reference
* count reaches 0.
*/
int driver_register(struct device_driver * drv)
{
klist_init(&drv->klist_devices, klist_devices_get, klist_devices_put);
init_completion(&drv->unloaded);
return bus_add_driver(drv);
}
/**
* driver_unregister - remove driver from system.
* @drv: driver.
*
* Again, we pass off most of the work to the bus-level call.
*
* Though, once that is done, we wait until @drv->unloaded is completed.
* This will block until the driver refcount reaches 0, and it is
* released. Only modular drivers will call this function, and we
* have to guarantee that it won't complete, letting the driver
* unload until all references are gone.
*/
void driver_unregister(struct device_driver * drv)
{
bus_remove_driver(drv);
wait_for_completion(&drv->unloaded);
}
/**
* driver_find - locate driver on a bus by its name.
* @name: name of the driver.
* @bus: bus to scan for the driver.
*
* Call kset_find_obj() to iterate over list of drivers on
* a bus to find driver by name. Return driver if found.
*
* Note that kset_find_obj increments driver's reference count.
*/
struct device_driver *driver_find(const char *name, struct bus_type *bus)
{
struct kobject *k = kset_find_obj(&bus->drivers, name);
if (k)
return to_drv(k);
return NULL;
}
EXPORT_SYMBOL_GPL(driver_register);
EXPORT_SYMBOL_GPL(driver_unregister);
EXPORT_SYMBOL_GPL(get_driver);
EXPORT_SYMBOL_GPL(put_driver);
EXPORT_SYMBOL_GPL(driver_find);
EXPORT_SYMBOL_GPL(driver_create_file);
EXPORT_SYMBOL_GPL(driver_remove_file);