[driver-core,v9,2/9] device core: Consolidate locking and unlocking of parent and device
diff mbox series

Message ID 154466190393.9126.148371211828405339.stgit@ahduyck-desk1.jf.intel.com
State Superseded
Headers show
Series
  • Add NUMA aware async_schedule calls
Related show

Commit Message

Alexander Duyck Dec. 13, 2018, 12:45 a.m. UTC
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.

This patch should produce no functional changes, it is meant to be a code
clean-up/consolidation only.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
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   |   95 ++++++++++++++++++++++++++++++++++++++++-----------
 3 files changed, 81 insertions(+), 39 deletions(-)

Comments

Rafael J. Wysocki Dec. 14, 2018, 10:40 a.m. UTC | #1
somOn Thu, Dec 13, 2018 at 1:45 AM Alexander Duyck
<alexander.h.duyck@linux.intel.com> wrote:
>
> 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.
>
> This patch should produce no functional changes, it is meant to be a code
> clean-up/consolidation only.
>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> 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   |   95 ++++++++++++++++++++++++++++++++++++++++-----------
>  3 files changed, 81 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 b886b15cb53b..74054481007d 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 */
> @@ -771,13 +761,8 @@ 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 74c194ac99df..f07c16277ed9 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -867,6 +867,64 @@ 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_unlock - 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 device has been removed or someone has already successfully
> +        * bound a driver before us just skip the driver probe call.
> +        */
> +       if (!dev->dead && !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;
> @@ -894,14 +952,7 @@ 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->dead && !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 +983,11 @@ static void __device_release_driver(struct device *dev, struct device *parent)
>         drv = dev->driver;
>         if (drv) {
>                 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

This change will clash with
https://patchwork.kernel.org/patch/10729571/ somewhat which really
should go it first as a stable-candidate fix.

I would suggest rebasing on top of that one, unless Greg has different
plans here.

> @@ -993,16 +1040,12 @@ 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 +1070,18 @@ 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.
>
Alexander Duyck Dec. 17, 2018, 4:31 p.m. UTC | #2
On Fri, 2018-12-14 at 11:40 +0100, Rafael J. Wysocki wrote:
>  somOn Thu, Dec 13, 2018 at 1:45 AM Alexander Duyck
> <alexander.h.duyck@linux.intel.com> wrote:
> > 
> > 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.
> > 
> > This patch should produce no functional changes, it is meant to be a code
> > clean-up/consolidation only.
> > 
> > Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> > 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   |   95 ++++++++++++++++++++++++++++++++++++++++-----------
> >  3 files changed, 81 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 b886b15cb53b..74054481007d 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 */
> > @@ -771,13 +761,8 @@ 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 74c194ac99df..f07c16277ed9 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -867,6 +867,64 @@ 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_unlock - 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 device has been removed or someone has already successfully
> > +        * bound a driver before us just skip the driver probe call.
> > +        */
> > +       if (!dev->dead && !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;
> > @@ -894,14 +952,7 @@ 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->dead && !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 +983,11 @@ static void __device_release_driver(struct device *dev, struct device *parent)
> >         drv = dev->driver;
> >         if (drv) {
> >                 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
> 
> This change will clash with
> https://patchwork.kernel.org/patch/10729571/ somewhat which really
> should go it first as a stable-candidate fix.
> 
> I would suggest rebasing on top of that one, unless Greg has different
> plans here.

Greg, any opinion here? From what I can tell the patch pointed out and
this one both address the same issue. The only real difference is that
the patch called out would be a better stable-candidate fix.

I'm just wondering if the patch set is good as is or if I need to be
submitting a v10 w/ rebase on top of this patch.

Thanks.

- Alex

Patch
diff mbox series

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 b886b15cb53b..74054481007d 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 */
@@ -771,13 +761,8 @@  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 74c194ac99df..f07c16277ed9 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -867,6 +867,64 @@  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_unlock - 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 device has been removed or someone has already successfully
+	 * bound a driver before us just skip the driver probe call.
+	 */
+	if (!dev->dead && !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;
@@ -894,14 +952,7 @@  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->dead && !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 +983,11 @@  static void __device_release_driver(struct device *dev, struct device *parent)
 	drv = dev->driver;
 	if (drv) {
 		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 +1040,12 @@  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 +1070,18 @@  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.