From e044a7def7f6aa61d3bb2a75a1ef597a4724441b Mon Sep 17 00:00:00 2001

From: William Cohen <wcohen@redhat.com>

Date: Mon, 18 Jun 2018 16:47:00 -0400

Subject: [PATCH] Initialize the trans structure fields to values unused by

 perf samples

On newer 4.14 kernel operf was crashing because the kernel commit

1d953111b648e ("perf/core: Don't report zero PIDs for exiting tasks")

made perf samples have TID/PID of -1 for exiting processes.  OProfile

used this same value internally to indicate the that field had not

been initialized.  As a result operf would incorrectly attempt to run

some bookkeeping code due to an invalid match. The initialization of

the trans tgid field is now changed to a value that is unsed by the

perf samples to ensure that these invalid matches do not occur.

Signed-off-by: William Cohen <wcohen@redhat.com>

---

 libperf_events/operf_utils.cpp | 9 ++++++++-

 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/libperf_events/operf_utils.cpp b/libperf_events/operf_utils.cpp

index 58c50a6..057692d 100644

--- a/libperf_events/operf_utils.cpp

+++ b/libperf_events/operf_utils.cpp

@@ -73,7 +73,14 @@ static inline void update_trans_last(struct operf_transient * trans)

 static inline void clear_trans(struct operf_transient * trans)

 {

-	trans->tgid = ~0U;

+	/* ~0U (-1) could be used by the kernel perf samples

+	 * for the TID/PID of exiting processes. To avoid

+	 * confusing the oprofile logic use ~1U as the

+	 * initialization value for tgid field to avoid

+	 * possibly matching the TID/PID values for exiting

+	 * processes.

+	 */

+	trans->tgid = ~1U;

 	trans->cur_procinfo = NULL;

 }

-- 

1.8.3.1