linux-kernel - Re: [PATCH v1 1/2] PM: runtime: Do not call __rpm_callback() from rpm

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Date:   Mon, 5 Dec 2022 09:45:06 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Tushar Nimkar <quic_tnimkar@...cinc.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Nitin Rawat <quic_nitirawa@...cinc.com>,
        Peter Wang <peter.wang@...iatek.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1 1/2] PM: runtime: Do not call __rpm_callback() from
 rpm_idle()

On 2/12/22 16:30, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Calling __rpm_callback() from rpm_idle() after adding device links
> support to the former is a clear mistake.
> 
> Not only it causes rpm_idle() to carry out unnecessary actions, but it
> is also against the assumption regarding the stability of PM-runtime
> status accross __rpm_callback() invocations, because rpm_suspend() and

accross -> across

> rpm_resume() may run in parallel with __rpm_callback() when it is called
> by rpm_idle() and the device's PM-runtime status can be updated by any
> of them.
> 
> Fixes: 21d5c57b3726 ("PM / runtime: Use device links")

Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>

> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/base/power/runtime.c |   12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -484,7 +484,17 @@ static int rpm_idle(struct device *dev,
>  
>  	dev->power.idle_notification = true;
>  
> -	retval = __rpm_callback(callback, dev);
> +	if (dev->power.irq_safe)
> +		spin_unlock(&dev->power.lock);
> +	else
> +		spin_unlock_irq(&dev->power.lock);
> +
> +	retval = callback(dev);
> +
> +	if (dev->power.irq_safe)
> +		spin_lock(&dev->power.lock);
> +	else
> +		spin_lock_irq(&dev->power.lock);
>  
>  	dev->power.idle_notification = false;
>  	wake_up_all(&dev->power.wait_queue);
> 
> 
>