linux-kernel - [PATCH] perf tools: rework of handling lack of sched

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Date:	Tue, 19 May 2015 15:20:47 +0200
From:	Petr Holasek <pholasek@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Petr Holasek <pholasek@...hat.com>
Subject: [PATCH] perf tools: rework of handling lack of sched_getcpu in old glibc

Commit e1e455f4f4d3 ("perf tools: Work around lack of sched_getcpu in
glibc < 2.6.") introduced weak function sched_getcpu() which should
be overridden by sched_getcpu() provided by glibc >= 2.6. Unfortunately,
the weak function was linked to sched_getcpu() used in perf bench numa
and made the benchmark heavily relying on this function unusable.

This patch alternates weak function magic for preprocessor defines.

Signed-off-by: Petr Holasek <pholasek@...hat.com>
---
 tools/perf/util/cloexec.c | 13 +++++++++++--
 tools/perf/util/cloexec.h |  6 ------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 85b5238..23b8aa9 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -7,11 +7,20 @@
 
 static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
 
-int __weak sched_getcpu(void)
+#ifdef __GLIBC_PREREQ
+#if !__GLIBC_PREREQ(2, 6)
+static int do_sched_getcpu(void)
 {
 	errno = ENOSYS;
 	return -1;
 }
+#else
+static int do_sched_getcpu(void)
+{
+	return sched_getcpu();
+}
+#endif
+#endif
 
 static int perf_flag_probe(void)
 {
@@ -27,7 +36,7 @@ static int perf_flag_probe(void)
 	pid_t pid = -1;
 	char sbuf[STRERR_BUFSIZE];
 
-	cpu = sched_getcpu();
+	cpu = do_sched_getcpu();
 	if (cpu < 0)
 		cpu = 0;
 
diff --git a/tools/perf/util/cloexec.h b/tools/perf/util/cloexec.h
index 68888c2..94a5a7d 100644
--- a/tools/perf/util/cloexec.h
+++ b/tools/perf/util/cloexec.h
@@ -3,10 +3,4 @@
 
 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 */
-- 
2.1.0

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