linux-kernel - Re: [PATCH 2/2] jump label: disable due to compiler bug

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Message-ID: <4CCB08EB.8070004@caviumnetworks.com>
Date:	Fri, 29 Oct 2010 10:48:27 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>, Jason Baron <jbaron@...hat.com>,
	rth@...hat.com, "H. Peter Anvin" <hpa@...or.com>,
	tglx@...utronix.de, andi@...stfloor.org, roland@...hat.com,
	masami.hiramatsu.pt@...achi.com, fweisbec@...il.com,
	avi@...hat.com, davem@...emloft.net, vgoyal@...hat.com,
	sam@...nborg.org, tony@...eyournoodle.com, dsd@...top.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] jump label: disable due to compiler bug

On 10/29/2010 10:33 AM, Steven Rostedt wrote:
> On Fri, 2010-10-29 at 10:18 -0700, David Daney wrote:
>
>> I hate to continue beating a dead horse, but RTH just committed the GCC
>> patch, and it will be part of GCC-4.5.2 and later.
>
> Great!
>
>>
>> Should this knowledge be builtin to the jump label enabling calculus?
>
> No, because we can't trust versions. We never know what home grown gcc a
> kernel developer is using (and what has been backported or not). Thus
> the only option is to have a builtin test we can do at compile time to
> determine if the bug exists or not and decide then.
>

The test case is in the GCC bug report, and is quite small:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46226

Perhaps it could be integrated with the current checks for the presence 
of 'asm goto'

> Note, I'm currently running my last set of patches through ktest. When
> it finishes (presumably with no issues), I'll post a pull request.
>
> -- Steve
>
>

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