linux-kernel - [RFC PATCH] dynamic_debug: Remove _

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Message-ID: <1337284958.17726.51.camel@joe2Laptop>
Date:	Thu, 17 May 2012 13:02:38 -0700
From:	Joe Perches <joe@...ches.com>
To:	Jason Baron <jbaron@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH] dynamic_debug: Remove __used attribute from metadata

The __used attribute in the declaration of the
dynamic_debug metadata stops the compiler from
optimizing and eliminating constant tests and
the metadata declaration used in things like:

   #define DEBUG_LEVEL 0
   if (DEBUG_LEVEL > 1)
   	pr_debug("foo...");

This is a common construct for debugging macros
with a constant "level" test.

When dynamic_debug is not configured, this is
pr_debug and format string is eliminated unless
DEBUG_LEVEL is greater than 1.

Remove the unnecessary __used attribute so the
even the dynamic_debug use of pr_debug can be
appropriately optimized away completely.

Signed-off-by: Joe Perches <joe@...ches.com>
---
 include/linux/dynamic_debug.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 7e3c53a..85cee11 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -58,7 +58,7 @@ int __dynamic_netdev_dbg(struct _ddebug *descriptor,
 			 const char *fmt, ...);
 
 #define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt)		\
-	static struct _ddebug __used __aligned(8)		\
+	static struct _ddebug __aligned(8)			\
 	__attribute__((section("__verbose"))) name = {		\
 		.modname = KBUILD_MODNAME,			\
 		.function = __func__,				\


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