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

Maurizio Lombardi
2026-03-23T10:10:31Z

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@redhat.com>
> Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
> Tested-by: Laurence Oberman <loberman@redhat.com>
> ---
> 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