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 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>

1 files changed, 7 insertions, 12 deletions

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 135231239103..3f32df7ed373 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 */