[PATCH] perf tools: Work around lack of sched_getcpu in glibc < 2.6.

[Vinson Lee <vlee@twopensource.com>]

From: Vinson Lee <vlee@twitter.com>

This patch fixes this build error with glibc < 2.6.

  CC       util/cloexec.o
cc1: warnings being treated as errors
util/cloexec.c: In function ‘perf_flag_probe’:
util/cloexec.c:24: error: implicit declaration of function
‘sched_getcpu’
util/cloexec.c:24: error: nested extern declaration of ‘sched_getcpu’
make: *** [util/cloexec.o] Error 1

Cc: stable@vger.kernel.org # 3.18+
Signed-off-by: Vinson Lee <vlee@twitter.com>
---
 tools/perf/util/cloexec.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 47b78b3..3738924 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -7,6 +7,12 @@
 
 static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
 
+#ifdef __GLIBC_PREREQ
+#if __GLIBC_PREREQ(2, 6)
+#define HAVE_SCHED_GETCPU
+#endif
+#endif
+
 static int perf_flag_probe(void)
 {
 	/* use 'safest' configuration as used in perf_evsel__fallback() */
@@ -21,9 +27,13 @@ static int perf_flag_probe(void)
 	pid_t pid = -1;
 	char sbuf[STRERR_BUFSIZE];
 
+#ifdef HAVE_SCHED_GETCPU
 	cpu = sched_getcpu();
 	if (cpu < 0)
 		cpu = 0;
+#else
+	cpu = 0;
+#endif
 
 	while (1) {
 		/* check cloexec flag */
-- 
1.8.2.1