Bug 10804

Summary:	/proc/sys/kernel/nmi_watchdog controls nmi_watchdog_enabled and not nmi_watchdog
Product:	Process Management	Reporter:	Ralph Corderoy (ralph)
Component:	Other	Assignee:	platform_i386
Status:	CLOSED DOCUMENTED
Severity:	normal	CC:	akpm, alan, chandragorentla, mingo
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.23	Subsystem:
Regression:	No	Bisected commit-id:

Description Ralph Corderoy 2008-05-27 03:15:12 UTC

nmi.c has two variables, nmi_watchdog and nmi_watchdog_enabled.  The
former can be set on the boot command line.  However, there's also a
/proc/sys/kernel/nmi_watchdog but confusingly this edits
nmi_watchdog_enabled and not the command line nmi_watchdog.  Can the
sysctl filename be changed to nmi_watchdog_enabled to match the code
and make it clear that the boot-time nmi_watchdog isn't being changed?

Frequent advice to users suffering hard hang-ups is to enable the
nmi_watchdog, there's evidence that them, and me, have to then puzzle
over why writing 2 to /proc/sys/kernel/nmi_watchdog isn't working.

Comment 1 Andrew Morton 2008-05-27 10:23:39 UTC

I'll reassign this to  platform_i386@kernel-bugs.osdl.org.

We'd prefer not to change the filename - it's now part of the
kernel->userspace interface and changing that is a big deal.

Is there some other way?

Comment 2 Ralph Corderoy 2008-05-28 07:25:25 UTC

OK, fair enough.  Is the boot command line more flexible in changing?  Perhaps its nmi_watchdog and the underlying nmi.c:nmi_watchdog variable could be renamed but I suspect not, in which case I can't see anything that can be done apart from user education.

Comment 3 Ingo Molnar 2008-05-28 12:27:35 UTC

there are two separate concepts here:

nmi_watchdog_enabled is the "user wish".

nmi_watchdog is the reality the kernel is able to offer.

Sometimes the two differ: user wants to set nmi_watchdog=1 but that's not possible. Ideally it should be possible to enable all NMI watchdog variants both from the command line and from the sysctl - patches are welcome. (and it's not a matter of changing a variable name)

Comment 4 Chandra 2008-08-26 01:34:04 UTC

(In reply to comment #3)
> there are two separate concepts here:
> 
> nmi_watchdog_enabled is the "user wish".
> 
> nmi_watchdog is the reality the kernel is able to offer.
> 
> Sometimes the two differ: user wants to set nmi_watchdog=1 but that's not
> possible. Ideally it should be possible to enable all NMI watchdog variants
> both from the command line and from the sysctl - patches are welcome. (and
> it's
> not a matter of changing a variable name)
> 

Is anybody working on this?  If not I want work on this.

Comment 5 Alan 2010-01-19 17:43:30 UTC

Closing old stale bugs