linux-kernel - Re: [PATCH v1 08/12] PM: sleep: stats: Use locking in dpm_save_failed

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Date: Thu, 25 Jan 2024 08:59:57 +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 08/12] PM: sleep: stats: Use locking in
 dpm_save_failed_dev()

On Mon, Jan 22, 2024 at 12:33:53PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Because dpm_save_failed_dev() may be called simultaneously by multiple
> failing device PM functions, the state of the suspend_stats fields
> updated by it may become inconsistent.
> 
> Prevent that from happening by using a lock in dpm_save_failed_dev().
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>

> ---
>  kernel/power/main.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> Index: linux-pm/kernel/power/main.c
> ===================================================================
> --- linux-pm.orig/kernel/power/main.c
> +++ linux-pm/kernel/power/main.c
> @@ -323,13 +323,18 @@ struct suspend_stats {
>  };
>  
>  static struct suspend_stats suspend_stats;
> +static DEFINE_MUTEX(suspend_stats_lock);
>  
>  void dpm_save_failed_dev(const char *name)
>  {
> +	mutex_lock(&suspend_stats_lock);
> +
>  	strscpy(suspend_stats.failed_devs[suspend_stats.last_failed_dev],
>  		name, sizeof(suspend_stats.failed_devs[0]));
>  	suspend_stats.last_failed_dev++;
>  	suspend_stats.last_failed_dev %= REC_FAILED_NUM;
> +
> +	mutex_unlock(&suspend_stats_lock);
>  }
>  
>  void dpm_save_failed_step(enum suspend_stat_step step)
> 
> 
> 
>