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Fix build errors due to CONFIG_BRANCH_TRACER=y

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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>
This commit is contained in:
Linus Torvalds 2009-04-07 07:59:41 -07:00
parent 985c0cd3f7
commit aeeae86859
1 changed files with 3 additions and 1 deletions
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4
include/linux/compiler.h
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@ -114,7 +114,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
* "Define 'is'", Bill Clinton * "Define 'is'", Bill Clinton
* "Define 'if'", Steven Rostedt * "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; \ int ______r; \
static struct ftrace_branch_data \ static struct ftrace_branch_data \