Messages in this thread | | | Date | Tue, 24 Feb 2015 10:46:33 -0500 | From | Don Zickus <> | Subject | Re: [PATCH 7/9] watchdog: enable the new user interface of the watchdog mechanism |
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On Mon, Feb 23, 2015 at 01:19:46PM -0800, Andrew Morton wrote: > 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/?
Ok.
> > Are all these changes back-compatible with previous kernel versions?
I believe so. The motivation for some of the change was the ambiguity of the /proc/sys/kerne/watchdog variable. This patchset clears that up. So if it breaks backward compatibility, it is because it was misinterpreted from its original intention.
Old definition of the proc/sys/kernel variable:
watchdog == nmi_watchdog_enabled
New definition:
watchdog == nmi_watchdog_enabled | softlockup_enabled
Cheers, Don
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