linux-kernel - Re: [PATCH v2] [watchdog] combine nmi

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Message-Id: <20100415153251.590c91ca.randy.dunlap@oracle.com>
Date:	Thu, 15 Apr 2010 15:32:51 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	mingo@...e.hu, fweisbec@...il.com, peterz@...radead.org,
	gorcunov@...il.com, aris@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] [watchdog] combine nmi_watchdog and softlockup

On Thu, 15 Apr 2010 17:25:10 -0400 Don Zickus wrote:

>  arch/x86/kernel/apic/hw_nmi.c |    2 +-
>  include/linux/sched.h         |    6 +
>  init/Kconfig                  |    1 +
>  kernel/Makefile               |    4 +-
>  kernel/sysctl.c               |    9 +
>  kernel/watchdog.c             |  570 +++++++++++++++++++++++++++++++++++++++++
>  lib/Kconfig.debug             |   21 +-
>  7 files changed, 605 insertions(+), 8 deletions(-)
>  create mode 100644 kernel/watchdog.c

Updates to Documentation/kernel-parameters.txt ??


> +static int __init no_watchdog_setup(char *str)
> +{
> +	no_watchdog = 1;
> +	return 1;
> +}
> +__setup("no_watchdog", no_watchdog_setup);

New, please document.

> +/* deprecated */
> +static int __init nosoftlockup_setup(char *str)
> +{
> +	no_watchdog = 1;
> +	return 1;
> +}

That's not marked as deprecated anywhere?

> +__setup("nosoftlockup", nosoftlockup_setup);
> +static int __init nonmi_watchdog_setup(char *str)
> +{
> +	no_watchdog = 1;
> +	return 1;
> +}
> +__setup("nonmi_watchdog", nonmi_watchdog_setup);

New, please document.


> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index e2e73cc..280794a 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -171,15 +171,24 @@ config DETECT_SOFTLOCKUP
>  	   support it.)
>  
>  config NMI_WATCHDOG
> -	bool "Detect Hard Lockups with an NMI Watchdog"
> -	depends on DEBUG_KERNEL && PERF_EVENTS && PERF_EVENTS_NMI
> +	bool "Detect Hard and Soft Lockups"
> +	depends on DEBUG_KERNEL
> +	default DETECT_SOFTLOCKUP
>  	help
>  	  Say Y here to enable the kernel to use the NMI as a watchdog
> -	  to detect hard lockups.  This is useful when a cpu hangs for no

	                                  preferably:    CPU

> -	  reason but can still respond to NMIs.  A backtrace is displayed
> -	  for reviewing and reporting.
> +	  to detect hard and soft lockups.
> +
> +	  Softlockups are bugs that cause the kernel to loop in kernel
> +	  mode for more than 60 seconds, without giving other tasks a
> +	  chance to run.  The current stack trace is displayed upon
> +	  detection and the system will stay locked up.
> +
> +	  Hardlockups are bugs that cause the cpu to loop in kernel mode

ditto

> +	  for more than 60 seconds, without letting other interrupts a

	                                                             have a

> +	  chance to run.  The current stack trace is displayed upon detection
> +	  and the system will stay locked up.
>  
> -	  The overhead should be minimal, just an extra NMI every few
> +	  The overhead should me minimal, just an extra NMI every few

	                      be

>  	  seconds.
>  
>  config BOOTPARAM_SOFTLOCKUP_PANIC


---
~Randy
--
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