Re: [PATCH] suspend: enable freeze timeout configuration through sysctl

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 29 Jan 2013 10:58:20 +0800
fli24 <fei.li@intel.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.