Re: [driver-core PATCH v9 2/9] device core: Consolidate locking and unlocking of parent and device

From: Rafael J. Wysocki
Date: Fri Dec 14 2018 - 05:40:40 EST

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somOn Thu, Dec 13, 2018 at 1:45 AM Alexander Duyck
<alexander.h.duyck@xxxxxxxxxxxxxxx> 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@xxxxxxxxxx>
> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> ---
> 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.
>

Next message: Claudiu.Beznea: "[PATCH v2] net: macb: restart tx after tx used bit read"
Previous message: Geert Uytterhoeven: "Re: [PATCH] i2c: sh_mobile: Add support for r8a774c0 (RZ/G2E)"
In reply to: Alexander Duyck: "[driver-core PATCH v9 2/9] device core: Consolidate locking and unlocking of parent and device"
Next in thread: Alexander Duyck: "[driver-core PATCH v9 4/9] workqueue: Provide queue_work_node to queue work near a given NUMA node"
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