linux-kernel - Re: [PATCH v1 11/12] PM: sleep: Move devices to new lists earlier in each suspend phase

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Date: Thu, 25 Jan 2024 09:00:47 +0100
From: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1 11/12] PM: sleep: Move devices to new lists earlier in
 each suspend phase

On Mon, Jan 22, 2024 at 12:42:46PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> During a system-wide suspend of devices, dpm_noirq_suspend_devices(),
> dpm_suspend_late() and dpm_suspend() move devices from one list to
> another.  They do it with each device after its PM callback in the
> given suspend phase has run or has been scheduled for asynchronous
> execution, in case it is deleted from the current list in the
> meantime.
> 
> However, devices can be moved to a new list before invoking their PM
> callbacks (which usually is the case for the devices whose callbacks
> are executed asynchronously anyway), because doing so does not affect
> the ordering of that list.  In either case, each device is moved to
> the new list after the previous device has been moved to it or gone
> away, and if a device is removed, it does not matter which list it is
> in at that point, because deleting an entry from a list does not change
> the ordering of the other entries in it.
> 
> Accordingly, modify the functions mentioned above to move devices to
> new lists without waiting for their PM callbacks to run regardless of
> whether or not they run asynchronously.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>

> ---
>  drivers/base/power/main.c |   24 +++---------------------
>  1 file changed, 3 insertions(+), 21 deletions(-)
> 
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -1304,18 +1304,12 @@ static int dpm_noirq_suspend_devices(pm_
>  	while (!list_empty(&dpm_late_early_list)) {
>  		struct device *dev = to_device(dpm_late_early_list.prev);
>  
> +		list_move(&dev->power.entry, &dpm_noirq_list);
>  		get_device(dev);
>  		mutex_unlock(&dpm_list_mtx);
>  
>  		error = device_suspend_noirq(dev);
>  
> -		mutex_lock(&dpm_list_mtx);
> -
> -		if (!error && !list_empty(&dev->power.entry))
> -			list_move(&dev->power.entry, &dpm_noirq_list);
> -
> -		mutex_unlock(&dpm_list_mtx);
> -
>  		put_device(dev);
>  
>  		mutex_lock(&dpm_list_mtx);
> @@ -1486,19 +1480,13 @@ int dpm_suspend_late(pm_message_t state)
>  	while (!list_empty(&dpm_suspended_list)) {
>  		struct device *dev = to_device(dpm_suspended_list.prev);
>  
> +		list_move(&dev->power.entry, &dpm_late_early_list);
>  		get_device(dev);
>  
>  		mutex_unlock(&dpm_list_mtx);
>  
>  		error = device_suspend_late(dev);
>  
> -		mutex_lock(&dpm_list_mtx);
> -
> -		if (!list_empty(&dev->power.entry))
> -			list_move(&dev->power.entry, &dpm_late_early_list);
> -
> -		mutex_unlock(&dpm_list_mtx);
> -
>  		put_device(dev);
>  
>  		mutex_lock(&dpm_list_mtx);
> @@ -1763,19 +1751,13 @@ int dpm_suspend(pm_message_t state)
>  	while (!list_empty(&dpm_prepared_list)) {
>  		struct device *dev = to_device(dpm_prepared_list.prev);
>  
> +		list_move(&dev->power.entry, &dpm_suspended_list);
>  		get_device(dev);
>  
>  		mutex_unlock(&dpm_list_mtx);
>  
>  		error = device_suspend(dev);
>  
> -		mutex_lock(&dpm_list_mtx);
> -
> -		if (!error && !list_empty(&dev->power.entry))
> -			list_move(&dev->power.entry, &dpm_suspended_list);
> -
> -		mutex_unlock(&dpm_list_mtx);
> -
>  		put_device(dev);
>  
>  		mutex_lock(&dpm_list_mtx);
> 
> 
> 
>