From aeeae86859f4319de0a4946b44771d9926eeed54 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 7 Apr 2009 07:59:41 -0700
Subject: [PATCH] Fix build errors due to CONFIG_BRANCH_TRACER=y
The code that enables branch tracing for all (non-constant) branches
plays games with the preprocessor and #define's the C 'if ()' construct
to do tracing.
That's all fine, but it fails for some unusual but valid C code that is
sometimes used in macros, notably by the intel-iommu code:
if (i=drhd->iommu, drhd->ignored) ..
because now the preprocessor complains about multiple arguments to the
'if' macro.
So make the macro expansion of this particularly horrid trick use
varargs, and handle the case of comma-expressions in if-statements. Use
another macro to do it cleanly in just one place.
This replaces a patch by David (and acked by Steven) that did this all
inside that one already-too-horrid macro.
Tested-by: Ingo Molnar <mingo@elte.hu>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/compiler.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 6faa7e549de4c..cebfdcd3dbddc 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -114,7 +114,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
* "Define 'is'", Bill Clinton
* "Define 'if'", Steven Rostedt
*/
-#define if(cond) if (__builtin_constant_p((cond)) ? !!(cond) : \
+#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
+#define __trace_if(cond) \
+ if (__builtin_constant_p((cond)) ? !!(cond) : \
({ \
int ______r; \
static struct ftrace_branch_data \
--
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