linux-kernel - Re: [PATCH 4/5 V2] usb: call pm_runtime_put_sync in pm_runtime_get

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Date:	Thu, 28 Feb 2013 10:17:02 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Li Fei <fei.li@...el.com>
cc:	gregkh@...uxfoundation.org, <tianyu.lan@...el.com>,
	<sarah.a.sharp@...ux.intel.com>, <rjw@...k.pl>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<chuansheng.liu@...el.com>
Subject: Re: [PATCH 4/5 V2] usb: call pm_runtime_put_sync in pm_runtime_get_sync
 failed case

On Thu, 28 Feb 2013, Li Fei wrote:

> 
> Even in failed case of pm_runtime_get_sync, the usage_count
> is incremented. In order to keep the usage_count with correct
> value and runtime power management to behave correctly, call
> pm_runtime_put(_sync) in such case.
> 
> Signed-off-by Liu Chuansheng <chuansheng.liu@...el.com>
> Signed-off-by: Li Fei <fei.li@...el.com>
> ---
>  drivers/usb/core/hub.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 5480352..f72dede 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3148,12 +3148,13 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>  
>  	if (port_dev->did_runtime_put) {
>  		status = pm_runtime_get_sync(&port_dev->dev);
> -		port_dev->did_runtime_put = false;
>  		if (status < 0) {
>  			dev_dbg(&udev->dev, "can't resume usb port, status %d\n",
>  					status);
> +			pm_runtime_put_sync(&port_dev->dev);
>  			return status;
>  		}
> +		port_dev->did_runtime_put = false;
>  	}

I don't see much point in this.  After a failed resume, the port's 
runtime PM status is undefined.  Whether or not you do a 
pm_runtime_put_sync won't make any difference.

Alan Stern

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