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Re: [PATCH 01/31] Add hard/soft lockup debugger entry points

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On 1/28/16, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 28 Jan 2016, Jeffrey Merkey wrote:
>
>> This patch series adds an export which can be set by system debuggers to
>> direct the hard lockup and soft lockup detector to trigger a breakpoint
>> exception and enter a debugger if one is active.  It is assumed that if
>> someone sets this variable, then an breakpoint handler of some sort will
>> be actively loaded or registered via the notify die handler chain.
>>
>> This addition is extremely useful for debugging hard and soft lockups
>> real time and quickly from a console debugger.
>
> Why do we need an extra breakpoint instruction in the code to enter a
> debugger? Don't have debuggers mechanisms to install breakpoints?
>
> I'm probably missing something obvious here.
>
> Thanks,
>
> 	tglx
>
>
>

It's a pain in the butt to grep around through assembly language in a
function in watchdog.c that has everything declared static with no
symbols.  It's a lot easier just to insert an INT3 in the section of
code that has the mouse caught in the trap (inside a function that
triggers the hard lockup) -- after all -- that's what the instruction
is for.

Jeff

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Thread

[PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-28 20:50 +0100
  Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Thomas Gleixner <tglx@linutronix.de> - 2016-01-28 21:00 +0100
    Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-28 21:10 +0100
      Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Thomas Gleixner <tglx@linutronix.de> - 2016-01-28 22:00 +0100
        Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-28 22:00 +0100
          Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Thomas Gleixner <tglx@linutronix.de> - 2016-01-28 23:10 +0100
            Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-28 23:30 +0100
          Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Ingo Molnar <mingo@kernel.org> - 2016-01-29 09:20 +0100
            Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-29 17:30 +0100
            Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-29 17:40 +0100
              Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-29 18:20 +0100
            Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-30 03:50 +0100
  Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Jeffrey Merkey <jeffmerkey@gmail.com> - 2016-01-28 21:50 +0100
  Re: [PATCH 01/31] Add hard/soft lockup debugger entry points Chris Metcalf <cmetcalf@ezchip.com> - 2016-01-28 23:20 +0100

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