perf tools: Convert to BACKTRACE_SUPPORT

For building perf without stack backtrace debug, we can set
NO_BACKTRACE=1 as a argument of make.  It then defines NO_BACKTRACE
macro for C code to do the proper handling.  However it usually used in
a negative semantics - e.g. #ifndef - so we saw double negations which
can be misleading.  Convert it to a positive form to make it more
readable and add _SUPPORT suffix for consistency.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Irina Tirdea <irina.tirdea@gmail.com>
Cc: Irina Tirdea <irina.tirdea@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1349109171-1942-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile

@@ -45,6 +45,8 @@ include config/utilities.mak
 #
 # Define NO_LIBUNWIND if you do not want libunwind dependency for dwarf
 # backtrace post unwind.
+#
+# Define NO_BACKTRACE if you do not want stack backtrace debug feature
 
 $(OUTPUT)PERF-VERSION-FILE: .FORCE-PERF-VERSION-FILE
 	@$(SHELL_PATH) util/PERF-VERSION-GEN $(OUTPUT)
@@ -749,11 +751,9 @@ ifndef NO_STRLCPY
 	endif
 endif
 
-ifdef NO_BACKTRACE
-       BASIC_CFLAGS += -DNO_BACKTRACE
-else
-       ifneq ($(call try-cc,$(SOURCE_BACKTRACE),),y)
-               BASIC_CFLAGS += -DNO_BACKTRACE
+ifndef NO_BACKTRACE
+       ifeq ($(call try-cc,$(SOURCE_BACKTRACE),),y)
+               BASIC_CFLAGS += -DBACKTRACE_SUPPORT
        endif
 endif
 

tools/perf/util/util.c

@@ -1,7 +1,7 @@
 #include "../perf.h"
 #include "util.h"
 #include <sys/mman.h>
-#ifndef NO_BACKTRACE
+#ifdef BACKTRACE_SUPPORT
 #include <execinfo.h>
 #endif
 #include <stdio.h>
@@ -165,7 +165,7 @@ size_t hex_width(u64 v)
 }
 
 /* Obtain a backtrace and print it to stdout. */
-#ifndef NO_BACKTRACE
+#ifdef BACKTRACE_SUPPORT
 void dump_stack(void)
 {
 	void *array[16];