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

[Babu Moger]

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