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Subject[driver-core PATCH v6 3/9] device core: Consolidate locking and unlocking of parent and device
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Try to consolidate all of the locking and unlocking of both the parent and
device when attaching or removing a driver from a given device.

To do that I first consolidated the lock pattern into two functions
__device_driver_lock and __device_driver_unlock. After doing that I then
created functions specific to attaching and detaching the driver while
acquiring these locks. By doing this I was able to reduce the number of
spots where we touch need_parent_lock from 12 down to 4.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
drivers/base/base.h | 2 +
drivers/base/bus.c | 23 ++-----------
drivers/base/dd.c | 91 ++++++++++++++++++++++++++++++++++++++++-----------
3 files changed, 77 insertions(+), 39 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index 7a419a7a6235..3f22ebd6117a 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -124,6 +124,8 @@ extern int driver_add_groups(struct device_driver *drv,
const struct attribute_group **groups);
extern void driver_remove_groups(struct device_driver *drv,
const struct attribute_group **groups);
+int device_driver_attach(struct device_driver *drv, struct device *dev);
+void device_driver_detach(struct device *dev);

extern char *make_class_name(const char *name, struct kobject *kobj);

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 8bfd27ec73d6..8a630f9bd880 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -184,11 +184,7 @@ static ssize_t unbind_store(struct device_driver *drv, const char *buf,

dev = bus_find_device_by_name(bus, NULL, buf);
if (dev && dev->driver == drv) {
- if (dev->parent && dev->bus->need_parent_lock)
- device_lock(dev->parent);
- device_release_driver(dev);
- if (dev->parent && dev->bus->need_parent_lock)
- device_unlock(dev->parent);
+ device_driver_detach(dev);
err = count;
}
put_device(dev);
@@ -211,13 +207,7 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,

dev = bus_find_device_by_name(bus, NULL, buf);
if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
- if (dev->parent && bus->need_parent_lock)
- device_lock(dev->parent);
- device_lock(dev);
- err = driver_probe_device(drv, dev);
- device_unlock(dev);
- if (dev->parent && bus->need_parent_lock)
- device_unlock(dev->parent);
+ err = device_driver_attach(drv, dev);

if (err > 0) {
/* success */
@@ -769,13 +759,8 @@ EXPORT_SYMBOL_GPL(bus_rescan_devices);
*/
int device_reprobe(struct device *dev)
{
- if (dev->driver) {
- if (dev->parent && dev->bus->need_parent_lock)
- device_lock(dev->parent);
- device_release_driver(dev);
- if (dev->parent && dev->bus->need_parent_lock)
- device_unlock(dev->parent);
- }
+ if (dev->driver)
+ device_driver_detach(dev);
return bus_rescan_devices_helper(dev, NULL);
}
EXPORT_SYMBOL_GPL(device_reprobe);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 169412ee4ae8..76c40fe69463 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -864,6 +864,60 @@ void device_initial_probe(struct device *dev)
__device_attach(dev, true);
}

+/*
+ * __device_driver_lock - acquire locks needed to manipulate dev->drv
+ * @dev: Device we will update driver info for
+ * @parent: Parent device. Needed if the bus requires parent lock
+ *
+ * This function will take the required locks for manipulating dev->drv.
+ * Normally this will just be the @dev lock, but when called for a USB
+ * interface, @parent lock will be held as well.
+ */
+static void __device_driver_lock(struct device *dev, struct device *parent)
+{
+ if (parent && dev->bus->need_parent_lock)
+ device_lock(parent);
+ device_lock(dev);
+}
+
+/*
+ * __device_driver_lock - release locks needed to manipulate dev->drv
+ * @dev: Device we will update driver info for
+ * @parent: Parent device. Needed if the bus requires parent lock
+ *
+ * This function will release the required locks for manipulating dev->drv.
+ * Normally this will just be the the @dev lock, but when called for a
+ * USB interface, @parent lock will be released as well.
+ */
+static void __device_driver_unlock(struct device *dev, struct device *parent)
+{
+ device_unlock(dev);
+ if (parent && dev->bus->need_parent_lock)
+ device_unlock(parent);
+}
+
+/**
+ * device_driver_attach - attach a specific driver to a specific device
+ * @drv: Driver to attach
+ * @dev: Device to attach it to
+ *
+ * Manually attach driver to a device. Will acquire both @dev lock and
+ * @dev->parent lock if needed.
+ */
+int device_driver_attach(struct device_driver *drv, struct device *dev)
+{
+ int ret = 0;
+
+ __device_driver_lock(dev, dev->parent);
+
+ if (!dev->driver)
+ ret = driver_probe_device(drv, dev);
+
+ __device_driver_unlock(dev, dev->parent);
+
+ return ret;
+}
+
static int __driver_attach(struct device *dev, void *data)
{
struct device_driver *drv = data;
@@ -891,14 +945,7 @@ static int __driver_attach(struct device *dev, void *data)
return ret;
} /* ret > 0 means positive match */

- if (dev->parent && dev->bus->need_parent_lock)
- device_lock(dev->parent);
- device_lock(dev);
- if (!dev->driver)
- driver_probe_device(drv, dev);
- device_unlock(dev);
- if (dev->parent && dev->bus->need_parent_lock)
- device_unlock(dev->parent);
+ device_driver_attach(drv, dev);

return 0;
}
@@ -932,15 +979,11 @@ static void __device_release_driver(struct device *dev, struct device *parent)
async_synchronize_full();

while (device_links_busy(dev)) {
- device_unlock(dev);
- if (parent)
- device_unlock(parent);
+ __device_driver_unlock(dev, parent);

device_links_unbind_consumers(dev);
- if (parent)
- device_lock(parent);

- device_lock(dev);
+ __device_driver_lock(dev, parent);
/*
* A concurrent invocation of the same function might
* have released the driver successfully while this one
@@ -993,16 +1036,12 @@ void device_release_driver_internal(struct device *dev,
struct device_driver *drv,
struct device *parent)
{
- if (parent && dev->bus->need_parent_lock)
- device_lock(parent);
+ __device_driver_lock(dev, parent);

- device_lock(dev);
if (!drv || drv == dev->driver)
__device_release_driver(dev, parent);

- device_unlock(dev);
- if (parent && dev->bus->need_parent_lock)
- device_unlock(parent);
+ __device_driver_unlock(dev, parent);
}

/**
@@ -1027,6 +1066,18 @@ void device_release_driver(struct device *dev)
}
EXPORT_SYMBOL_GPL(device_release_driver);

+/**
+ * device_driver_detach - detach driver from a specific device
+ * @dev: device to detach driver from
+ *
+ * Detach driver from device. Will acquire both @dev lock and @dev->parent
+ * lock if needed.
+ */
+void device_driver_detach(struct device *dev)
+{
+ device_release_driver_internal(dev, NULL, dev->parent);
+}
+
/**
* driver_detach - detach driver from all devices it controls.
* @drv: driver.
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