Merge "simpleperf: write -1 to perf_event_paranoid when running as root." am: 668878b3b7

am: df104e1ed8

Change-Id: I56f126547cac5741c93513b9a2581be551da6034

1 files changed, 5 insertions, 2 deletions

diff --git a/simpleperf/environment.cpp b/simpleperf/environment.cpp
index d0cb8351..7fff85f1 100644
--- a/simpleperf/environment.cpp
+++ b/simpleperf/environment.cpp
@@ -361,8 +361,11 @@ static const char* GetLimitLevelDescription(int limit_level) {
 }
 
 bool CheckPerfEventLimit() {
-  // root is not limited by /proc/sys/kernel/perf_event_paranoid.
-  if (IsRoot()) {
+  // Root is not limited by /proc/sys/kernel/perf_event_paranoid. However, the monitored threads
+  // may create child processes not running as root. To make sure the child processes have
+  // enough permission to create inherited tracepoint events, write -1 to perf_event_paranoid.
+  // See http://b/62230699.
+  if (IsRoot() && android::base::WriteStringToFile("-1", "/proc/sys/kernel/perf_event_paranoid")) {
     return true;
   }
   int limit_level;