linux-kernel - Re: [RFC PATCH 0/4] Clean up watchdog handlers

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Date:   Tue, 1 Nov 2016 09:58:02 -0500
From:   Babu Moger <babu.moger@...cle.com>
To:     Don Zickus <dzickus@...hat.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, bp@...e.de,
        bywxiaobai@....com, cmetcalf@...lanox.com, keescook@...omium.org,
        ebiederm@...ssion.com, huawei.libin@...wei.com,
        ralf@...ux-mips.org, dvyukov@...gle.com,
        linux-kernel@...r.kernel.org, sam@...nborg.org
Subject: Re: [RFC PATCH 0/4] Clean up watchdog handlers


On 11/1/2016 8:20 AM, Don Zickus wrote:
> On Mon, Oct 31, 2016 at 04:30:59PM -0500, Babu Moger wrote:
>> On 10/31/2016 4:00 PM, Don Zickus wrote:
>>> On Wed, Oct 26, 2016 at 09:02:19AM -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 is the previous discussion
>>>> http://www.spinics.net/lists/sparclinux/msg16441.html
>>> Hi Babu,
>>>
>>> I finally got some cycles to poke at this today.  Good work.  A couple of
>>> suggestions.  For bisectability, I am thinking patch2 should be first and
>>> patch1 and patch3 should be combined.  Also watchdog_hld.c is going to need
>>> up top:
>>>
>>> #define pr_fmt(fmt) "NMI watchdog: " fmt
>>>
>>> otherwise the error messages miss the header.
>>>
>>> Though I don't think watchdog.c and watchdog_hld.c should have the same
>>> header.  A good solution isn't coming to me right now.  I will try to run
>>> some tests on this tomorrow.
>> Don, Thanks for the feedback. Let me know if you run into problems with your
>> tests.
> Hi Babu,
>
> My tests passed.  I just have to tweak the expected output lines as they
> constantly change. :-(
>
> I am going to play with different config options to see if things break from
> a compile perspective.

Don, Great. Thanks for the update.  I had couple of compilation issues 
with different config options.

1. 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.  Thinking of moving the 
definition of hrtimer_interrupts and is_hardlockup
into watchdog.c as softlockup code does most of the work here.

2. 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.
Will post the v2 version soon with all the comments included.

Thanks
Babu
>
>> I will start working on the comments.
> Great.
>
> Cheers,
> Don
>
>> Thanks
>> Babu
>>
>>> Cheers,
>>> Don
>>>
>>>> Babu Moger (4):
>>>>    watchdog: Remove hardlockup handler references
>>>>    watchdog: Move shared definitions to nmi.h
>>>>    watchdog: Move hardlockup detector in separate file
>>>>    sparc: Implement watchdog_nmi_enable and watchdog_nmi_disable
>>>>
>>>>   arch/sparc/kernel/nmi.c |   44 ++++++++-
>>>>   include/linux/nmi.h     |   19 ++++
>>>>   kernel/Makefile         |    1 +
>>>>   kernel/watchdog.c       |  276 ++---------------------------------------------
>>>>   kernel/watchdog_hld.c   |  238 ++++++++++++++++++++++++++++++++++++++++
>>>>   5 files changed, 312 insertions(+), 266 deletions(-)
>>>>   create mode 100644 kernel/watchdog_hld.c
>>>>