linux-kernel - RE: [PATCH] suspend: enable freeze timeout configuration through sysctl

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Message-ID: <BEC9F67575FA1E429CA7CF5AE9BE36343F06BF@SHSMSX102.ccr.corp.intel.com>
Date:	Wed, 30 Jan 2013 06:23:11 +0000
From:	"Li, Fei" <fei.li@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"rjw@...k.pl" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Subject: RE: [PATCH] suspend: enable freeze timeout configuration through
 sysctl

Hello Andrew,
   Thanks for your feedback.
   Your suggestion are all accepted, and will be updated in V2 as below:
1> The newly added attribute will be /sys/power/pm_freeze_timeout;
2> Documentation/power/freezing-of-tasks.txt will be updated to record such attribute;
3> Unit of millisecond will be used for the attribute. 

Best Regards,
Li Fei

-----Original Message-----
From: Andrew Morton [mailto:akpm@...ux-foundation.org] 
Sent: Wednesday, January 30, 2013 8:37 AM
To: Li, Fei
Cc: rjw@...k.pl; linux-kernel@...r.kernel.org; linux-pm@...r.kernel.org; Liu, Chuansheng
Subject: Re: [PATCH] suspend: enable freeze timeout configuration through sysctl

On Tue, 29 Jan 2013 10:58:20 +0800
fli24 <fei.li@...el.com> wrote:

> At present, the timeout value for freezing tasks is fixed as 20s,
> which is too long for handheld device usage, especially for mobile
> phone.
> 
> In order to improve user experience, we enable freeze timeout
> configuration through sysctl, so that we can tune the value easily
> for concrete usage, such as smaller value for handheld device such
> as mobile phone.
> 
> ...
>

The patch looks nice - it does everything right in places where things
are frequently done wrongly.  Except..

It forgot to document the sysctl.  Documentation/sysctl/kernel.txt, I
guess.

Is /proc/sys/kernel the most appropriate place for this?  Perhaps a
PM-specific place would be better.  Maybe not.

> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -13,6 +13,11 @@ extern bool pm_freezing;		/* PM freezing in effect */
>  extern bool pm_nosig_freezing;		/* PM nosig freezing in effect */
>  
>  /*
> + * Timeout for stopping processes
> + */
> +extern unsigned int sysctl_freeze_process_timeout_secs;

I suggest the use of milliseconds here.  Someone might want a
half-second timeout and it's pretty pointless to design the interface
in a way which rules that out.

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