perf tools: Use __maybe_used for unused variables

perf defines both __used and __unused variables to use for marking
unused variables. The variable __used is defined to
__attribute__((__unused__)), which contradicts the kernel definition to
__attribute__((__used__)) for new gcc versions. On Android, __used is
also defined in system headers and this leads to warnings like: warning:
'__used__' attribute ignored

__unused is not defined in the kernel and is not a standard definition.
If __unused is included everywhere instead of __used, this leads to
conflicts with glibc headers, since glibc has a variables with this name
in its headers.

The best approach is to use __maybe_unused, the definition used in the
kernel for __attribute__((unused)). In this way there is only one
definition in perf sources (instead of 2 definitions that point to the
same thing: __used and __unused) and it works on both Linux and Android.
This patch simply replaces all instances of __used and __unused with
__maybe_unused.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1347315303-29906-7-git-send-email-irina.tirdea@intel.com
[ committer note: fixed up conflict with a116e05 in builtin-sched.c ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bench/bench.h

@@ -3,7 +3,8 @@
 
 extern int bench_sched_messaging(int argc, const char **argv, const char *prefix);
 extern int bench_sched_pipe(int argc, const char **argv, const char *prefix);
-extern int bench_mem_memcpy(int argc, const char **argv, const char *prefix __used);
+extern int bench_mem_memcpy(int argc, const char **argv,
+			    const char *prefix __maybe_unused);
 extern int bench_mem_memset(int argc, const char **argv, const char *prefix);
 
 #define BENCH_FORMAT_DEFAULT_STR	"default"

tools/perf/bench/mem-memcpy.c

@@ -177,7 +177,7 @@ static double do_memcpy_gettimeofday(memcpy_t fn, size_t len, bool prefault)
 	} while (0)
 
 int bench_mem_memcpy(int argc, const char **argv,
-		     const char *prefix __used)
+		     const char *prefix __maybe_unused)
 {
 	int i;
 	size_t len;

tools/perf/bench/mem-memset.c

@@ -171,7 +171,7 @@ static double do_memset_gettimeofday(memset_t fn, size_t len, bool prefault)
 	} while (0)
 
 int bench_mem_memset(int argc, const char **argv,
-		     const char *prefix __used)
+		     const char *prefix __maybe_unused)
 {
 	int i;
 	size_t len;

tools/perf/bench/sched-messaging.c

@@ -267,7 +267,7 @@ static const char * const bench_sched_message_usage[] = {
 };
 
 int bench_sched_messaging(int argc, const char **argv,
-		    const char *prefix __used)
+		    const char *prefix __maybe_unused)
 {
 	unsigned int i, total_children;
 	struct timeval start, stop, diff;

tools/perf/bench/sched-pipe.c

@@ -43,7 +43,7 @@ static const char * const bench_sched_pipe_usage[] = {
 };
 
 int bench_sched_pipe(int argc, const char **argv,
-		     const char *prefix __used)
+		     const char *prefix __maybe_unused)
 {
 	int pipe_1[2], pipe_2[2];
 	int m = 0, i;
@@ -55,8 +55,8 @@ int bench_sched_pipe(int argc, const char **argv,
 	 * discarding returned value of read(), write()
 	 * causes error in building environment for perf
 	 */
-	int __used ret, wait_stat;
-	pid_t pid, retpid __used;
+	int __maybe_unused ret, wait_stat;
+	pid_t pid, retpid __maybe_unused;
 
 	argc = parse_options(argc, argv, options,
 			     bench_sched_pipe_usage, 0);