[PATCH v3] 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 | 6 ++++++
 tools/perf/util/cloexec.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 6da965b..85b5238 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;
 
+int __weak sched_getcpu(void)
+{
+	errno = ENOSYS;
+	return -1;
+}
+
 static int perf_flag_probe(void)
 {
 	/* use 'safest' configuration as used in perf_evsel__fallback() */
diff --git a/tools/perf/util/cloexec.h b/tools/perf/util/cloexec.h
index 94a5a7d..68888c2 100644
--- a/tools/perf/util/cloexec.h
+++ b/tools/perf/util/cloexec.h
@@ -3,4 +3,10 @@
 
 unsigned long perf_event_open_cloexec_flag(void);
 
+#ifdef __GLIBC_PREREQ
+#if !__GLIBC_PREREQ(2, 6)
+extern int sched_getcpu(void) __THROW;
+#endif
+#endif
+
 #endif /* __PERF_CLOEXEC_H */
-- 
1.8.2.1