[PATCH V4] PM / core: fix deferred probe breaking suspend resume order

[Rafael J. Wysocki]

On Wednesday, April 11, 2018 1:57:06 AM CEST Feng Kan wrote:
> When bridge and its endpoint is enumerated the devices are added to the
> dpm list. Afterward, the bridge defers probe when IOMMU is not ready.
> This causes the bridge to be moved to the end of the dpm list when
> deferred probe kicks in. The order of the dpm list for bridge and
> endpoint is reversed.
> 
> Add reordering code to move the bridge and its children and consumers to
> the end of the pm list so the order for suspend and resume is not altered.
> The code also move device and its children and consumers to the tail of
> device_kset list if it is registered.
> 
> Signed-off-by: Feng Kan <fkan at apm.com>
> Signed-off-by: Toan Le <toanle at apm.com>

I'm going to queue this up for 4.18-rc1.

If anyone, and Greg in particular, has any objections of concerns regarding
that, please let me know.

> ---
>  V4:
> 	1. additional comment change from Rafael
>  V3:
> 	1. additional code comment changes
>  V2:
>         1. change patch title from "move device and its children..."
>         2. move define based on Bjorn's comment
>         3. rename function name and comment content
> 
>  drivers/base/base.h |  3 +++
>  drivers/base/core.c | 20 ++++++++++++++++++++
>  drivers/base/dd.c   |  4 +---
>  3 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/base.h b/drivers/base/base.h
> index d800de6..a75c302 100644
> --- a/drivers/base/base.h
> +++ b/drivers/base/base.h
> @@ -161,3 +161,6 @@ static inline void module_remove_driver(struct device_driver *drv) { }
>  extern void device_links_no_driver(struct device *dev);
>  extern bool device_links_busy(struct device *dev);
>  extern void device_links_unbind_consumers(struct device *dev);
> +
> +/* device pm support */
> +void device_pm_move_to_tail(struct device *dev);
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 110230d..eaa5d9f 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -148,6 +148,26 @@ static int device_reorder_to_tail(struct device *dev, void *not_used)
>  }
>  
>  /**
> + * device_pm_move_to_tail - Move set of devices to the end of device lists
> + * @dev: Device to move
> + *
> + * This is a device_reorder_to_tail() wrapper taking the requisite locks.
> + *
> + * It moves the @dev along with all of its children and all of its consumers
> + * to the ends of the device_kset and dpm_list, recursively.
> + */
> +void device_pm_move_to_tail(struct device *dev)
> +{
> +	int idx;
> +
> +	idx = device_links_read_lock();
> +	device_pm_lock();
> +	device_reorder_to_tail(dev, NULL);
> +	device_pm_unlock();
> +	device_links_read_unlock(idx);
> +}
> +
> +/**
>   * device_link_add - Create a link between two devices.
>   * @consumer: Consumer end of the link.
>   * @supplier: Supplier end of the link.
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 2c964f5..96fab29 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -123,9 +123,7 @@ static void deferred_probe_work_func(struct work_struct *work)
>  		 * the list is a good order for suspend but deferred
>  		 * probe makes that very unsafe.
>  		 */
> -		device_pm_lock();
> -		device_pm_move_last(dev);
> -		device_pm_unlock();
> +		device_pm_move_to_tail(dev);
>  
>  		dev_dbg(dev, "Retrying from deferred list\n");
>  		if (initcall_debug && !initcalls_done)
>