linux-kernel - Re: [PATCH 1/3] KGDB: Major refactoring

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Date:	Thu, 07 Feb 2008 08:47:55 +0100
From:	Jan Kiszka <jan.kiszka@....de>
To:	Jason Wessel <jason.wessel@...driver.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kgdb-bugreport@...ts.sourceforge.net,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 1/3] KGDB: Major refactoring

Jason Wessel wrote:
> Ingo Molnar wrote:
>> * Jan Kiszka <jan.kiszka@....de> wrote:
>>
>>   
>>> As most changes are tightly coupled, this refactoring patch for
>>> KGDB_8250 as well as the core and the new KGDBOC driver comes as a
>>> single chunk. The changes are:
>>>  - Reorganized configuration: I/O drivers can be independently
>>>    configured as module or built-in
>>>  - Dynamic reconfiguration for KGDB_8250 (just like for KGDBOC)
>>>  - Reworked KGDB_8250 configuration string format
>>>  - attachwait removed, arming the debugger via assigning an I/O driver
>>>    implies "attachwait"
>>>  - Cleaned up I/O driver managment of the core
>>>  - Matured the various boot-up, configure, unconfigure code paths for
>>>    both I/O drivers
>>>  - IRQ vs. KGDB_CONSOLE-output SMP race fixed for KGDB_8250
>>>  - Reduced and cleaned up hooks into serial_core/8250
>>>  - Kconfig cleanups
>>>     
>> great stuff! I've picked these cleanups up into x86.git. (will pick up 
>> Jason's commits too)
>>
>> Could you try something else too perhaps, which would be way useful for 
>> me: to add a sysctl flag (or something like that) to change kgdboc to 
>> accept a Ctrl-C and break into kgdb mode? [this means a simple Ctrl-C on 
>> a kgdboc line would break into KGDB as well - but that would be an 
>> acceptable price.] Right now kgdboc just hangs when gdb attaches - i 
>> have to generate a SysRq sequence via a terminal emulator to break it 
>> into KGDB mode.
>>   
> 
> FYI, even if you were to hack in a control-c vs sysrq, gdb will still

And quite a bit of "hacking" would be required here, because the sysrq
hook is built upon the assumption that a hardware break starts the
sequence, not that just a single special character comes in. Changing
this means changing the drivers, not just some central hook function.

> hang on connect because it does not issue a break of any kind when it
> connects.  It assumes the connection is in a usable state.
> 
> The proxy spliter automatically sends the break (or in the current case
> the sysrq g)
>> This would make kgdboc way more practical without having to resort to a 
>> protocol splitting proxy, etc.
>>
>> 	Ingo
>>   
> 
> 
> Jason.

Jan


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