Re: [PATCH v3 0/2] Introduce arch specific nmi enable, disable handlers

From: Don Zickus
Date: Tue Oct 18 2016 - 16:03:13 EST

On Tue, Oct 18, 2016 at 12:14:08PM -0700, Babu Moger wrote:
> During our testing we noticed that nmi watchdogs in sparc could not be disabled or
> enabled dynamically using sysctl/proc interface. Sparc uses its own arch specific
> nmi watchdogs. There is a sysctl and proc interface(proc/sys/kernel/nmi_watchdog)
> to enable/disable nmi watchdogs. However, that is not working for sparc. There
> is no interface to feed this parameter to arch specific nmi watchdogs.
> These patches extend the same sysctl/proc interface to enable or disable
> these arch specific nmi watchdogs dynamically. Introduced new functions
> arch_watchdog_nmi_enable and arch_watchdog_nmi_disable which can be implemented
> in arch specific handlers.
> If you think there is a better way to do this. Please advice.
> Tested on sparc. Compile tested on x86.

Thanks Babu!

Tested-and-Reviewed-by: Don Zickus <dzickus@xxxxxxxxxx>

> v3:
> Made one more change per Don Zickus comments.
> Moved failure path messages to into generic code inside watchdog_nmi_enable.
> Also added matching prints in sparc to warn about the failure.
> v2:
> a)Sam Ravnborg's comments about making the definitions visible.
> With the new approach we dont need those definitions((NMI_WATCHDOG_ENABLED,
> SOFT_WATCHDOG_ENABLED etc..) outside watchdog.c. So no action.
> b) Made changes per Don Zickus comments.
> Don, I could not use your patches as is. Reason is sparc does not define
> CONFIG_HARDLOCKUP_DETECTOR. So, defining default __weak function did not
> work for me. However, I have used your idea to define __weak functions
> arch_watchdog_nmi_enable and arch_watchdog_nmi_disable when CONFIG_HARDLOCKUP_DETECTOR
> is not defined. I feel this should have very less impact on the races you are
> concerned about. Please take a look. Feel free to suggest.
> Patch2 changes: I had to introduce new variable nmi_init_done to synchronize
> watchdog thread and kernel init thread.
> v1:
> Initial version. Discussion thread here
> Babu Moger (2):
> watchdog: Introduce arch_watchdog_nmi_enable and
> arch_watchdog_nmi_disable
> sparc: Implement arch_watchdog_nmi_enable and
> arch_watchdog_nmi_disable
> arch/sparc/kernel/nmi.c | 44 +++++++++++++++++++++++++++++-
> kernel/watchdog.c | 69 +++++++++++++++++++++++++++++++---------------
> 2 files changed, 89 insertions(+), 24 deletions(-)