Re: [PATCH 3/5] driver core: async device shutdown infrastructure

[Maurizio Lombardi]

On Thu Mar 19, 2026 at 3:11 PM CET, David Jeffery wrote:
> Patterned after async suspend, allow devices to mark themselves as wanting
> to perform async shutdown. Devices using async shutdown wait only for their
> dependencies to shutdown before executing their shutdown routine.
>
> Sync shutdown devices are shut down one at a time and will only wait for an
> async shutdown device if the async device is a dependency.
>
> Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
> Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
> Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
> ---
>  drivers/base/base.h    |   2 +
>  drivers/base/core.c    | 104 ++++++++++++++++++++++++++++++++++++++++-
>  include/linux/device.h |  13 ++++++
>  3 files changed, 118 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/base.h b/drivers/base/base.h
> index 79d031d2d845..ea2a039e7907 100644
> --- a/drivers/base/base.h
> +++ b/drivers/base/base.h
> @@ -113,6 +113,7 @@ struct driver_type {
>   * @device - pointer back to the struct device that this structure is
>   * associated with.
>   * @driver_type - The type of the bound Rust driver.
> + * @complete - completion for device shutdown ordering
>   * @dead - This device is currently either in the process of or has been
>   *	removed from the system. Any asynchronous events scheduled for this
>   *	device should exit without taking any action.
> @@ -132,6 +133,7 @@ struct device_private {
>  #ifdef CONFIG_RUST
>  	struct driver_type driver_type;
>  #endif
> +	struct completion complete;
>  	u8 dead:1;
>  };
>  #define to_device_private_parent(obj)	\
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 2e9094f5c5aa..53568b820a13 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -9,6 +9,7 @@
>   */
>  
>  #include <linux/acpi.h>
> +#include <linux/async.h>
>  #include <linux/blkdev.h>
>  #include <linux/cleanup.h>
>  #include <linux/cpufreq.h>
> @@ -37,6 +38,10 @@
>  #include "physical_location.h"
>  #include "power/power.h"
>  
> +static bool async_shutdown = true;
> +module_param(async_shutdown, bool, 0644);
> +MODULE_PARM_DESC(async_shutdown, "Enable asynchronous device shutdown support");
> +
>  /* Device links support. */
>  static LIST_HEAD(deferred_sync);
>  static unsigned int defer_sync_state_count = 1;
> @@ -3538,6 +3543,7 @@ static int device_private_init(struct device *dev)
>  	klist_init(&dev->p->klist_children, klist_children_get,
>  		   klist_children_put);
>  	INIT_LIST_HEAD(&dev->p->deferred_probe);
> +	init_completion(&dev->p->complete);
>  	return 0;
>  }
>  
> @@ -4782,6 +4788,37 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
>  	return error;
>  }
>  
> +static bool wants_async_shutdown(struct device *dev)
> +{
> +	return async_shutdown && dev->async_shutdown;
> +}
> +
> +static int wait_for_device_shutdown(struct device *dev, void *data)
> +{
> +	bool async = *(bool *)data;
> +
> +	if (async || wants_async_shutdown(dev))
> +		wait_for_completion(&dev->p->complete);
> +
> +	return 0;
> +}
> +
> +static void wait_for_shutdown_dependencies(struct device *dev, bool async)
> +{
> +	struct device_link *link;
> +	int idx;
> +
> +	device_for_each_child(dev, &async, wait_for_device_shutdown);
> +
> +	idx = device_links_read_lock();
> +
> +	dev_for_each_link_to_consumer(link, dev)
> +		if (!device_link_flag_is_sync_state_only(link->flags))
> +			wait_for_device_shutdown(link->consumer, &async);
> +
> +	device_links_read_unlock(idx);
> +}
> +
>  static void __shutdown_one_device(struct device *dev)
>  {
>  	device_lock(dev);
> @@ -4805,6 +4842,8 @@ static void __shutdown_one_device(struct device *dev)
>  		dev->driver->shutdown(dev);
>  	}
>  
> +	complete_all(&dev->p->complete);
> +
>  	device_unlock(dev);
>  }
>  
> @@ -4823,6 +4862,58 @@ static void shutdown_one_device(struct device *dev)
>  	put_device(dev);
>  }
>  
> +static void async_shutdown_handler(void *data, async_cookie_t cookie)
> +{
> +	struct device *dev = data;
> +
> +	wait_for_shutdown_dependencies(dev, true);
> +	shutdown_one_device(dev);
> +}
> +
> +static bool shutdown_device_async(struct device *dev)
> +{
> +	if (async_schedule_dev_nocall(async_shutdown_handler, dev))
> +		return true;
> +	return false;
> +}
> +
> +
> +static void early_async_shutdown_devices(void)
> +{
> +	struct device *dev, *next, *needs_put = NULL;
> +
> +	if (!async_shutdown)
> +		return;
> +
> +	spin_lock(&devices_kset->list_lock);
> +
> +	list_for_each_entry_safe_reverse(dev, next, &devices_kset->list,
> +					 kobj.entry) {
> +		if (wants_async_shutdown(dev)) {
> +			get_device(dev->parent);
> +			get_device(dev);
> +
> +			if (shutdown_device_async(dev)) {
> +				list_del_init(&dev->kobj.entry);
> +			} else {
> +				/*
> +				 * async failed, clean up extra references
> +				 * and run from the standard shutdown loop
> +				 */
> +				needs_put = dev;
> +				break;
> +			}
> +		}
> +	}
> +
> +	spin_unlock(&devices_kset->list_lock);
> +
> +	if (needs_put) {
> +		put_device(needs_put->parent);
> +		put_device(needs_put);
> +	}
> +}
> +
>  /**
>   * device_shutdown - call ->shutdown() on each device to shutdown.
>   */
> @@ -4835,6 +4926,12 @@ void device_shutdown(void)
>  
>  	cpufreq_suspend();
>  
> +	/*
> +	 * Start async device threads where possible to maximize potential
> +	 * parallelism and minimize false dependency on unrelated sync devices
> +	 */
> +	early_async_shutdown_devices();
> +
>  	spin_lock(&devices_kset->list_lock);
>  	/*
>  	 * Walk the devices list backward, shutting down each in turn.
> @@ -4859,11 +4956,16 @@ void device_shutdown(void)
>  		list_del_init(&dev->kobj.entry);
>  		spin_unlock(&devices_kset->list_lock);
>  
> -		shutdown_one_device(dev);
> +		if (!wants_async_shutdown(dev) || !shutdown_device_async(dev)) {
> +			wait_for_shutdown_dependencies(dev, false);
> +			shutdown_one_device(dev);
> +		}
>  
>  		spin_lock(&devices_kset->list_lock);
>  	}
>  	spin_unlock(&devices_kset->list_lock);
> +
> +	async_synchronize_full();
>  }
>  
>  /*
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 0be95294b6e6..da1db7d235c9 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -551,6 +551,8 @@ struct device_physical_location {
>   * @dma_skip_sync: DMA sync operations can be skipped for coherent buffers.
>   * @dma_iommu: Device is using default IOMMU implementation for DMA and
>   *		doesn't rely on dma_ops structure.
> + * @async_shutdown: Device shutdown may be run asynchronously and in parallel
> + *		to the shutdown of unrelated devices
>   *
>   * At the lowest level, every device in a Linux system is represented by an
>   * instance of struct device. The device structure contains the information
> @@ -669,6 +671,7 @@ struct device {
>  #ifdef CONFIG_IOMMU_DMA
>  	bool			dma_iommu:1;
>  #endif
> +	bool			async_shutdown:1;
>  };
>  
>  /**
> @@ -824,6 +827,16 @@ static inline bool device_async_suspend_enabled(struct device *dev)
>  	return !!dev->power.async_suspend;
>  }
>  
> +static inline bool device_enable_async_shutdown(struct device *dev)
> +{
> +	return dev->async_shutdown = true;
> +}

Shouldn't this function just return void?

Maurizio