linux-kernel - Re: [PATCH v2 0/3] Clean up watchdog handlers

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Message-ID: <20161104162523.GU35881@redhat.com>
Date:   Fri, 4 Nov 2016 12:25:23 -0400
From:   Don Zickus <dzickus@...hat.com>
To:     Babu Moger <babu.moger@...cle.com>
Cc:     mingo@...nel.org, akpm@...ux-foundation.org, ak@...ux.intel.com,
        jkosina@...e.cz, baiyaowei@...s.chinamobile.com,
        atomlin@...hat.com, uobergfe@...hat.com, tj@...nel.org,
        hidehiro.kawai.ez@...achi.com, johunt@...mai.com,
        davem@...emloft.net, sparclinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, sam@...nborg.org
Subject: Re: [PATCH v2 0/3] Clean up watchdog handlers

On Tue, Nov 01, 2016 at 02:13:43PM -0700, Babu Moger wrote:
> This is an attempt to cleanup watchdog handlers. Right now,
> kernel/watchdog.c implements both softlockup and hardlockup detectors.
> Softlockup code is generic. Hardlockup code is arch specific. Some
> architectures don't use hardlockup detectors. They use their own watchdog
> detectors. To make both these combination work, we have numerous #ifdefs
> in kernel/watchdog.c.
> 
> We are trying here to make these handlers independent of each other.
> Also provide an interface for architectures to implement their own
> handlers. watchdog_nmi_enable and watchdog_nmi_disable will be defined
> as weak such that architectures can override its definitions.
> 
> Thanks to Don Zickus for his suggestions.
> Here are our previous discussions
> http://www.spinics.net/lists/sparclinux/msg16543.html
> http://www.spinics.net/lists/sparclinux/msg16441.html
> 

Hi Babu,

Thanks for the patches.  It passes my panic/reboot testing.  The patches
look good for now.  Though this change has me thinking about other cleanup
changes I can make on top of this.  But I am going to hold off for now until
we are sure nothing really broke.  As this should be a straight forward
split.

The only odd thing for me is I am having trouble disabling
CONFIG_HARDLOCKUP_DETECTOR.  For some reason def_bool y, is forcing the
option on despite my repeated attempts to disable it.  I had to rename the
option to do some test compiling and verify it doesn't regress when
disabled.  Probably my environment..

Thanks for the work Babu!

Acked-by: Don Zickus <dzickus@...hat.com>


> v2:
>   Addressed few comments from Don Zickus.
>   1. Took care of bisectability issue. Previous patch2 is patch1 now.
>      Combined patch 1 and 3. Patch 4 is now patch 3.
>   2. Added pr_fmt back in watchdog_hld.c
>   3. Tweaked the file headers for watchdog.c and watchdog_hld.c.
> 
>   4. Took care of couple of config compile issues.
> 
>    drivers/edac/edac_device.o:(.discard+0x0): multiple definition of `__pcpu_unique_hrtimer_interrupts'
>    drivers/edac/edac_mc.o:(.discard+0x0): first defined here
>    This was a problem with uni processor config. Moved the definition of hrtimer_interrupts and
>    is_hardlockup into watchdog.c as softlockup code does most of the work here.
>    is_hardlockup kind of generic most part.
> 
>    kernel/built-in.o: In function `watchdog_overflow_callback':
>    watchdog_hld.c:(.text+0x56940): undefined reference to `sysctl_hardlockup_all_cpu_backtrace'
>    Moved this definition to nmi.h.
> 
> v1:
>   Initial version
> Babu Moger (3):
>   watchdog: Move shared definitions to nmi.h
>   watchdog: Move hardlockup detector to separate file
>   sparc: Implement watchdog_nmi_enable and watchdog_nmi_disable
> 
>  arch/sparc/kernel/nmi.c |   44 ++++++++-
>  include/linux/nmi.h     |   24 ++++
>  kernel/Makefile         |    1 +
>  kernel/watchdog.c       |  270 +++--------------------------------------------
>  kernel/watchdog_hld.c   |  227 +++++++++++++++++++++++++++++++++++++++
>  5 files changed, 310 insertions(+), 256 deletions(-)
>  create mode 100644 kernel/watchdog_hld.c
>