[PATCH 32/61] driver core: check bus->match without holding device lock

Greg Kroah-Hartman
2009-03-25T00:41:16Z

From: Ming Lei <tom.leiming@gmail.com>

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 6cd495860901,
which leads to a faster boot. But the commit 6cd495860901 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: Ming Lei <tom.leiming@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/base/base.h | 5 +++++
drivers/base/bus.c | 2 +-
drivers/base/dd.c | 19 +++++++------------
3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 9f50f1b..ca2b037 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -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);

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 83f32b8..8547b78 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -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);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 1352312..3f32df7 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -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 */
--
1.6.2