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>

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index c5d05ec..6a37be5 100644 (file)
--- 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,