linux-kernel - Re: [2.6.29] Fix for enabling branch profiling makes sparse unusable

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Message-ID: <e2e108260904081029u621e46bbmc95cff280f70085c@mail.gmail.com>
Date:	Wed, 8 Apr 2009 19:29:38 +0200
From:	Bart Van Assche <bart.vanassche@...il.com>
To:	Steven Rostedt <srostedt@...hat.com>, Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.29] Fix for enabling branch profiling makes sparse unusable

On Sun, Apr 5, 2009 at 4:20 PM, Bart Van Assche
<bart.vanassche@...il.com> wrote:
> One of the changes between kernels 2.6.28 and 2.6.29 is that a branch profiler
> has been added for if() statements. Unfortunately this patch makes the sparse
> output unusable with CONFIG_TRACE_BRANCH_PROFILING=y: when branch profiling is
> enabled, sparse prints so much false positives that the real issues are no
> longer visible. This behavior can be reproduced as follows:
> * enable CONFIG_TRACE_BRANCH_PROFILING, e.g. by running make allyesconfig or
>  make allmodconfig.
> * run make C=2
>
> Result: a huge number of the following sparse warnings.
> ...
> include/linux/cpumask.h:547:2: warning: symbol '______r' shadows an earlier one
> include/linux/cpumask.h:547:2: originally declared here
> ...
>
> The patch below fixes this by disabling branch profiling while analyzing the
> kernel code with sparse.
>
> See also:
> * http://lkml.org/lkml/2008/11/21/18
> * http://bugzilla.kernel.org/show_bug.cgi?id=12925
>
> Signed-off-by: Bart Van Assche <bart.vanassche@...il.com>
>
> --- orig/linux-2.6.29/include/linux/compiler.h  2009-03-23 19:12:14.000000000 -0400
> +++ linux-2.6.29/include/linux/compiler.h       2009-03-24 08:46:46.000000000 -0400
> @@ -75,7 +75,8 @@ struct ftrace_branch_data {
>  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
>  * to disable branch tracing on a per file basis.
>  */
> -#if defined(CONFIG_TRACE_BRANCH_PROFILING) && !defined(DISABLE_BRANCH_PROFILING)
> +#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
> +    && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
>  void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
>
>  #define likely_notrace(x)      __builtin_expect(!!(x), 1)

(ping)

Hello,

Is there any chance the above patch will get included in the 2.6.30 kernel ?

Bart.
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