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Subject[PATCH v3 0/2] Introduce arch specific nmi enable, disable handlers
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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.

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
http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1245427.html

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(-)

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