Commit 49b420a1 authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman
Browse files

driver core: check bus->match without holding device lock 



This patch moves bus->match out from driver_probe_device and
does not hold device lock to check the match between a device
and a driver.

The idea has been verified by the commit 6cd49586,
which leads to a faster boot. But the commit 6cd49586 has
the following drawbacks: 1),only does the quick check in
the path of __driver_attach->driver_probe_device, not in other
paths; 2),for a matched device and driver, check the same match
twice. It is a waste of cpu ,especially for some drivers with long
device id table (eg. usb-storage driver).

This patch adds a helper of driver_match_device to check the match
in all paths, and testes the match only once.

Signed-off-by: default avatarMing Lei <tom.leiming@gmail.com>
Acked-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 4a67a1bc

drivers/base/base.h

+5 −0
Original line number Diff line number Diff line
@@ -86,6 +86,11 @@ extern void bus_remove_driver(struct device_driver *drv); 


extern void driver_detach(struct device_driver *drv);

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

static inline int driver_match_device(struct device_driver *drv,

				      struct device *dev)

{

	return drv->bus->match && drv->bus->match(dev, drv);

}



extern void sysdev_shutdown(void);

drivers/base/bus.c

+1 −1
Original line number Diff line number Diff line
@@ -198,7 +198,7 @@ static ssize_t driver_bind(struct device_driver *drv, 
	int err = -ENODEV;



	dev = bus_find_device_by_name(bus, NULL, buf);

	if (dev && dev->driver == NULL) {

	if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {

		if (dev->parent)	/* Needed for USB */

			down(&dev->parent->sem);

		down(&dev->sem);

drivers/base/dd.c

+7 −12
Original line number Diff line number Diff line
@@ -189,14 +189,8 @@ int wait_for_device_probe(void) 
 * @drv: driver to bind a device to

 * @dev: device to try to bind to the driver

 *

 * 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, -ENODEV if the device is

 * not registered, and 0 otherwise.

 * This function returns -ENODEV if the device is not registered,

 * 1 if the device is bound sucessfully 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.
@@ -207,21 +201,22 @@ int driver_probe_device(struct device_driver *drv, struct device *dev) 


	if (!device_is_registered(dev))

		return -ENODEV;

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

		goto done;



	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",

		 drv->bus->name, __func__, dev_name(dev), drv->name);



	ret = really_probe(dev, drv);



done:

	return ret;

}



static int __device_attach(struct device_driver *drv, void *data)

{

	struct device *dev = data;



	if (!driver_match_device(drv, dev))

		return 0;



	return driver_probe_device(drv, dev);

}
@@ -274,7 +269,7 @@ static int __driver_attach(struct device *dev, void *data) 
	 * is an error.

	 */



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

	if (!driver_match_device(drv, dev))

		return 0;



	if (dev->parent)	/* Needed for USB */

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