[tip:perf/core] perf tools: Fix jump label always changing during tracing

tip-bot for Adrian Hunter
2014-07-28T08:24:03Z

Commit-ID: deaff8b659cf4d34181c087b8cdf74f1eb17b02b
Gitweb: http://git.kernel.org/tip/deaff8b659cf4d34181c087b8cdf74f1eb17b02b
Author: Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Tue, 22 Jul 2014 16:17:10 +0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 23 Jul 2014 11:12:59 -0300

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@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1406035081-14301-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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,