linux-kernel - Re: [PATCH v2 08/10] PM: sleep: Move some assignments from under a lock

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Date: Tue, 30 Jan 2024 08:21:30 +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 v2 08/10] PM: sleep: Move some assignments from under a
 lock

On Mon, Jan 29, 2024 at 05:27:33PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The async_error and pm_transition variables are set under dpm_list_mtx
> in multiple places in the system-wide device PM core code, which is
> unnecessary and confusing, so rearrange the code so that the variables
> in question are set before acquiring the lock.
> 
> While at it, add some empty code lines around locking to improve the
> consistency of the code.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>

> ---
> 
> v1 -> v2: No changes.
> 
> ---
>  drivers/base/power/main.c |   28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> Index: linux-pm/drivers/base/power/main.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/main.c
> +++ linux-pm/drivers/base/power/main.c
> @@ -707,9 +707,9 @@ static void dpm_noirq_resume_devices(pm_
>  	trace_suspend_resume(TPS("dpm_resume_noirq"), state.event, true);
>  
>  	async_error = 0;
> +	pm_transition = state;
>  
>  	mutex_lock(&dpm_list_mtx);
> -	pm_transition = state;
>  
>  	/*
>  	 * Trigger the resume of "async" devices upfront so they don't have to
> @@ -847,9 +847,9 @@ void dpm_resume_early(pm_message_t state
>  	trace_suspend_resume(TPS("dpm_resume_early"), state.event, true);
>  
>  	async_error = 0;
> +	pm_transition = state;
>  
>  	mutex_lock(&dpm_list_mtx);
> -	pm_transition = state;
>  
>  	/*
>  	 * Trigger the resume of "async" devices upfront so they don't have to
> @@ -1012,10 +1012,11 @@ void dpm_resume(pm_message_t state)
>  	trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>  	might_sleep();
>  
> -	mutex_lock(&dpm_list_mtx);
>  	pm_transition = state;
>  	async_error = 0;
>  
> +	mutex_lock(&dpm_list_mtx);
> +
>  	/*
>  	 * Trigger the resume of "async" devices upfront so they don't have to
>  	 * wait for the "non-async" ones they don't depend on.
> @@ -1294,10 +1295,12 @@ static int dpm_noirq_suspend_devices(pm_
>  	int error = 0;
>  
>  	trace_suspend_resume(TPS("dpm_suspend_noirq"), state.event, true);
> -	mutex_lock(&dpm_list_mtx);
> +
>  	pm_transition = state;
>  	async_error = 0;
>  
> +	mutex_lock(&dpm_list_mtx);
> +
>  	while (!list_empty(&dpm_late_early_list)) {
>  		struct device *dev = to_device(dpm_late_early_list.prev);
>  
> @@ -1320,7 +1323,9 @@ static int dpm_noirq_suspend_devices(pm_
>  		if (error || async_error)
>  			break;
>  	}
> +
>  	mutex_unlock(&dpm_list_mtx);
> +
>  	async_synchronize_full();
>  	if (!error)
>  		error = async_error;
> @@ -1470,11 +1475,14 @@ int dpm_suspend_late(pm_message_t state)
>  	int error = 0;
>  
>  	trace_suspend_resume(TPS("dpm_suspend_late"), state.event, true);
> -	wake_up_all_idle_cpus();
> -	mutex_lock(&dpm_list_mtx);
> +
>  	pm_transition = state;
>  	async_error = 0;
>  
> +	wake_up_all_idle_cpus();
> +
> +	mutex_lock(&dpm_list_mtx);
> +
>  	while (!list_empty(&dpm_suspended_list)) {
>  		struct device *dev = to_device(dpm_suspended_list.prev);
>  
> @@ -1498,7 +1506,9 @@ int dpm_suspend_late(pm_message_t state)
>  		if (error || async_error)
>  			break;
>  	}
> +
>  	mutex_unlock(&dpm_list_mtx);
> +
>  	async_synchronize_full();
>  	if (!error)
>  		error = async_error;
> @@ -1745,9 +1755,11 @@ int dpm_suspend(pm_message_t state)
>  	devfreq_suspend();
>  	cpufreq_suspend();
>  
> -	mutex_lock(&dpm_list_mtx);
>  	pm_transition = state;
>  	async_error = 0;
> +
> +	mutex_lock(&dpm_list_mtx);
> +
>  	while (!list_empty(&dpm_prepared_list)) {
>  		struct device *dev = to_device(dpm_prepared_list.prev);
>  
> @@ -1771,7 +1783,9 @@ int dpm_suspend(pm_message_t state)
>  		if (error || async_error)
>  			break;
>  	}
> +
>  	mutex_unlock(&dpm_list_mtx);
> +
>  	async_synchronize_full();
>  	if (!error)
>  		error = async_error;
> 
> 
> 
>