[patch 12/51] Fix for enabling branch profiling makes sparse unusable

Greg KH
2009-05-14T22:46:11Z

[-- Attachment #1: fix-for-enabling-branch-profiling-makes-sparse-unusable.patch --]
[-- Type: text/plain, Size: 2052 bytes --]

2.6.29-stable review patch. If anyone has any objections, please let us know.

------------------

From: Bart Van Assche <bart.vanassche@gmail.com>

commit d9ad8bc0ca823705413f75b50c442a88cc518b35 upstream.

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.

This patch is already included in 2.6.30-rc1 -- see also
http://lkml.org/lkml/2009/4/5/120.

Signed-off-by: Bart Van Assche <bart.vanassche@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <200904051620.02311.bart.vanassche@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/compiler.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -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)