linux-kernel - Re: [PATCH] Add hard/soft lockup debugger entry points

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Message-ID: <CAO6TR8Um0A=XyTARjLVSxVCGBL3ZCC54BJ8Pfw90dws7KCSzWQ@mail.gmail.com>
Date:	Mon, 25 Jan 2016 19:58:03 -0700
From:	Jeff Merkey <linux.mdb@...il.com>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Don Zickus <dzickus@...hat.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Aaron Tomlin <atomlin@...hat.com>,
	Michal Hocko <mhocko@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Tejun Heo <tj@...nel.org>,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Subject: Re: [PATCH] Add hard/soft lockup debugger entry points

On 1/25/16, Chris Metcalf <cmetcalf@...hip.com> wrote:
> On 1/25/2016 9:36 PM, Jeff Merkey wrote:
>> This patch adds an export which can be set by system debuggers to direct
>> the hard lockup and soft lockup detector to trigger an INT3 exception
>> and enter a debugger if one is active.  It is assumed that if someone
>> sets this variable, then an int3 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.
>>
>> Signed-off-by: Jeff Merkey<linux.mdb@...il.com>
>> ---
>>   kernel/watchdog.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>
> Introducing Intel-specific assembly into generic code won't work. You would
> need to add a framework to allow platforms to specify a debugging
> instruction
> or maybe leverage some existing framework like arch_kgdb_breakpoint.
>
> --
> Chris Metcalf, EZChip Semiconductor
> http://www.ezchip.com
>
>

Yep.  I'll start on v2.

Jeff