Re: [PATCH 7/9] watchdog: enable the new user interface of the watchdog mechanism

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

On Thu,  5 Feb 2015 15:40:23 -0500 Don Zickus <dzickus@redhat.com> wrote:

> From: Ulrich Obergfell <uobergfe@redhat.com>
> 
> With the current user interface of the watchdog mechanism it is only
> possible to disable or enable both lockup detectors at the same time.
> This series introduces new kernel parameters and changes the semantics
> of some existing kernel parameters, so that the hard lockup detector
> and the soft lockup detector can be disabled or enabled individually.
> With this series applied, the user interface is as follows.
> 
> - parameters in /proc/sys/kernel
> 
>   . soft_watchdog
>     This is a new parameter to control and examine the run state of
>     the soft lockup detector.
> 
>   . nmi_watchdog
>     The semantics of this parameter have changed. It can now be used
>     to control and examine the run state of the hard lockup detector.
> 
>   . watchdog
>     This parameter is still available to control the run state of both
>     lockup detectors at the same time. If this parameter is examined,
>     it shows the logical OR of soft_watchdog and nmi_watchdog.
> 
>   . watchdog_thresh
>     The semantics of this parameter are not affected by the patch.
> 
> - kernel command line parameters
> 
>   . nosoftlockup
>     The semantics of this parameter have changed. It can now be used
>     to disable the soft lockup detector at boot time.
> 
>   . nmi_watchdog=0 or nmi_watchdog=1
>     Disable or enable the hard lockup detector at boot time. The patch
>     introduces '=1' as a new option.
> 
>   . nowatchdog
>     The semantics of this parameter are not affected by the patch. It
>     is still available to disable both lockup detectors at boot time.

So we need a whole bunch of updates and additions to Documentation/?

Are all these changes back-compatible with previous kernel versions?