linux-kernel - Re: [PATCH v2] Fix INT1 Exception with unregistered breakpoints

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Message-ID: <9ADACBE2-9CAA-4993-BF03-502DEF0D365D@zytor.com>
Date:	Mon, 14 Dec 2015 20:49:40 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeff Merkey <linux.mdb@...il.com>, linux-kernel@...r.kernel.org
CC:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	peterz@...radead.org, luto@...nel.org
Subject: Re: [PATCH v2] Fix INT1 Exception with unregistered breakpoints

On December 14, 2015 4:49:51 PM PST, Jeff Merkey <linux.mdb@...il.com> wrote:
>On 12/14/15, Jeff Merkey <linux.mdb@...il.com> wrote:
>> Please consider the attached patch.
>>
>> SUMMARY
>>
>> This patch corrects a hard lockup failure of the system kernel if the
>> operating system receives a breakpoint exception at a code execution
>> address which was not registered with the operating system.  The
>patch
>> allows kernel debuggers, application profiling and performance
>modules,
>> and external debugging tools to work better together at sharing the
>> breakpoint registers on the platform in a way that they do not cause
>> errors and system faults, and enables the full feature set in the
>> breakpoint API.  If a kernel application triggers a breakpoint
>> or programs one in error, this patch will catch the condition and
>report
>> it to the system log without the operating system experiencing a
>system
>> fault.  There are several consumers of the Linux Breakpoint API and
>all
>> of them can and sometimes do cause the condition this patch corrects.
>>
>
>Peter,
>
>Is that the type of summary that meets the standards.  I tried to be
>concise.
>
>Jeff

It would be good if you could be a bit more precise.  In particular, explain how and why the condition can appear rather than just explain that it can.
-- 
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