watchdog: enable the new user interface of the watchdog mechanism

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.

Also, remove the proc_dowatchdog() function which is no longer needed.

[dzickus@redhat.com: wrote changelog]
[dzickus@redhat.com: update documentation for kernel params and sysctl]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 01aa47d3b6ab..71eecb263250 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2236,8 +2236,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
 			Format: [panic,][nopanic,][num]
-			Valid num: 0
+			Valid num: 0 or 1
 			0 - turn nmi_watchdog off
+			1 - turn nmi_watchdog on
 			When panic is specified, panic when an NMI watchdog
 			timeout occurs (or 'nopanic' to override the opposite
 			default).
@@ -2464,7 +2465,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nousb		[USB] Disable the USB subsystem
 
-	nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
+	nowatchdog	[KNL] Disable both lockup detectors, i.e.
+                        soft-lockup and NMI watchdog (hard-lockup).
 
 	nowb		[ARM]