linux-kernel - [PATCH 01/52] perf tools: Fix jump label always changing during tracing

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Date:	Tue, 22 Jul 2014 16:17:10 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: [PATCH 01/52] perf tools: Fix jump label always changing during tracing

Intel PT decoding walks the object code to reconstruct
the trace.  A jump label change during tracing causes
decoding errors.

The "Enable close-on-exec flag on perf file descriptor"
patch caused there to be always a jump label change.

It was found that using a per-cpu context instead of a
per-thread context for the probe of the close-on-exec
feature, made the problem go away.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/util/cloexec.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index c5d05ec..6a37be5 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -1,3 +1,4 @@
+#include <sched.h>
 #include "util.h"
 #include "../perf.h"
 #include "cloexec.h"
@@ -14,9 +15,13 @@ static int perf_flag_probe(void)
 	};
 	int fd;
 	int err;
+	int cpu = sched_getcpu();
+
+	if (cpu < 0)
+		cpu = 0;
 
 	/* check cloexec flag */
-	fd = sys_perf_event_open(&attr, 0, -1, -1,
+	fd = sys_perf_event_open(&attr, -1, cpu, -1,
 				 PERF_FLAG_FD_CLOEXEC);
 	err = errno;
 
@@ -30,7 +35,7 @@ static int perf_flag_probe(void)
 		  err, strerror(err));
 
 	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
-	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
+	fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
 	err = errno;
 
 	if (WARN_ONCE(fd < 0,
-- 
1.8.3.2

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