From: Rafael J. Wysocki <[email protected]>
Notice that devices can be moved to dpm_prepared_list before running
their resume callbacks, in analogy with dpm_noirq_resume_devices() and
dpm_resume_early(), because doing so will not affect the final ordering
of that list.
Namely, if a device is the first dpm_suspended_list entry while
dpm_list_mtx is held, it has not been removed so far and it cannot be
removed until dpm_list_mtx is released, so moving it to dpm_prepared_list
at that point is valid. If it is removed later, while its resume
callback is running, it will be deleted from dpm_prepared_list without
changing the ordering of the other devices in that list.
Accordingly, rearrange the while () loop in dpm_resume() to move
devices to dpm_prepared_list before running their resume callbacks and
implify the locking and device reference counting in it.
No intentional functional impact.
Signed-off-by: Rafael J. Wysocki <[email protected]>
---
drivers/base/power/main.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -1017,25 +1017,19 @@ void dpm_resume(pm_message_t state)
while (!list_empty(&dpm_suspended_list)) {
dev = to_device(dpm_suspended_list.next);
-
- get_device(dev);
+ list_move_tail(&dev->power.entry, &dpm_prepared_list);
if (!dev->power.async_in_progress) {
+ get_device(dev);
+
mutex_unlock(&dpm_list_mtx);
device_resume(dev, state, false);
+ put_device(dev);
+
mutex_lock(&dpm_list_mtx);
}
-
- if (!list_empty(&dev->power.entry))
- list_move_tail(&dev->power.entry, &dpm_prepared_list);
-
- mutex_unlock(&dpm_list_mtx);
-
- put_device(dev);
-
- mutex_lock(&dpm_list_mtx);
}
mutex_unlock(&dpm_list_mtx);
async_synchronize_full();
On Mon, Jan 22, 2024 at 12:22:38PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <[email protected]>
>
> Notice that devices can be moved to dpm_prepared_list before running
> their resume callbacks, in analogy with dpm_noirq_resume_devices() and
> dpm_resume_early(), because doing so will not affect the final ordering
> of that list.
>
> Namely, if a device is the first dpm_suspended_list entry while
> dpm_list_mtx is held, it has not been removed so far and it cannot be
> removed until dpm_list_mtx is released, so moving it to dpm_prepared_list
> at that point is valid. If it is removed later, while its resume
> callback is running, it will be deleted from dpm_prepared_list without
> changing the ordering of the other devices in that list.
>
> Accordingly, rearrange the while () loop in dpm_resume() to move
> devices to dpm_prepared_list before running their resume callbacks and
> implify the locking and device reference counting in it.
>
> No intentional functional impact.
>
> Signed-off-by: Rafael J. Wysocki <[email protected]>
Reviewed-by: Stanislaw Gruszka <[email protected]>
> ---
> drivers/base/power/main.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -1017,25 +1017,19 @@ void dpm_resume(pm_message_t state)
>
> while (!list_empty(&dpm_suspended_list)) {
> dev = to_device(dpm_suspended_list.next);
> -
> - get_device(dev);
> + list_move_tail(&dev->power.entry, &dpm_prepared_list);
>
> if (!dev->power.async_in_progress) {
> + get_device(dev);
> +
> mutex_unlock(&dpm_list_mtx);
>
> device_resume(dev, state, false);
>
> + put_device(dev);
> +
> mutex_lock(&dpm_list_mtx);
> }
> -
> - if (!list_empty(&dev->power.entry))
> - list_move_tail(&dev->power.entry, &dpm_prepared_list);
> -
> - mutex_unlock(&dpm_list_mtx);
> -
> - put_device(dev);
> -
> - mutex_lock(&dpm_list_mtx);
> }
> mutex_unlock(&dpm_list_mtx);
> async_synchronize_full();
>
>
>