linux-kernel - Re: [PATCH -tip 5/7] perf probe: Query basic types from debuginfo

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Date:	Mon, 29 Mar 2010 18:05:03 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...radead.org>
CC:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH -tip 5/7] perf probe: Query basic types from debuginfo



Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 29, 2010 at 05:22:00PM -0400, Masami Hiramatsu escreveu:
>> Arnaldo Carvalho de Melo wrote:
>>> Em Mon, Mar 29, 2010 at 04:38:29PM -0400, Masami Hiramatsu escreveu:
>>> Question, should we use the equivalent to panic'ing the kernel in the
>>> userspace bits in tools/?
> 
>>> I tend to see all code there as potentially part of a library, i.e. to
>>> be callable by some unantecipated new tool or library that would rather
>>> receive a return value telling it that the operation can't be performed
>>> for some reason so that it can inform the user instead of having the
>>> whole tool exit to the command line.
>>
>> OK, so that you want to see 
>>
>> ret = library_func();
>> if (ret < 0)	/* Something wrong happened */
>> 	return ret;
>>
>> instead of 
>>
>> library_func();
>> hopefully_executed_next_func();
> 
> Exactly. That was my _suggestion_ :-)
>  
>>> It may well be that some specific operation needs lots of resources but
>>> many other don't, panic'c because the one that requires lots of
>>> resources can't be performed, bringing down a gui/tui is really nasty.
>>
>> Hmm, agreed. But I'd like to have some API for storing dying^H^H^H^H^Herror
>> message. (maybe can we use setjump/longjump approach - like try/cache - for die()?)
> 
> Can't we do just as we do in the kernel and propagate the error back to
> callers? All the way to userspace, that in this case would be the user
> instead of an app started by a user?  :-)
> 
> Wrt api for storing messages, we have pr_{warning,error,debug}, etc, in
> the TUI mode it is even redirected to the bottom line and I plan to have
> them get into something browseable if the user wants to see the last pr_
> messages.

Ah, that's very nice:)
OK, I'll try to use it and remove all 'die()'s.

Thank you!

> 
> IOW, just act like you're writing kernel code, that will make it more
> likely that people that are used to writing code like that will feel at
> ease while hacking tools/.
> 
> - Arnaldo
> --
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-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
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