commit 355ff8c7c15310df1159e2a9290c50d24317c600
author Hridya Valsaraju <hridya@google.com> Sat Sep 12 15:37:39 2020 -0700
committer Hridya Valsaraju <hridya@google.com> Mon Sep 14 20:04:43 2020 +0000
tree 4266986481cd15d9f69e3273f8d83668b8c09dce
parent 72a0f10f518a981d67612c6832a86f03c586c877

libcutils must check /sys/kernel/tracing for tracefs first

Currently it falls back to /sys/kernel/tracing if debugfs is not found.
/sys/kernel/tracing must be checked first since debugfs is not allowed
to be mounted in user builds starting with Android R launching devices.

Test: manual
Change-Id: I2fb5ec91bbf7d5304a1a6efcb06530969485e78f

libcutils/trace-dev.cpp

diff --git a/libcutils/trace-dev.cpp b/libcutils/trace-dev.cpp
index 5a09a2d..1ab63dc 100644
--- a/libcutils/trace-dev.cpp
+++ b/libcutils/trace-dev.cpp
@@ -30,9 +30,9 @@
 
 static void atrace_init_once()
 {
-    atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
+    atrace_marker_fd = open("/sys/kernel/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
     if (atrace_marker_fd == -1) {
-        atrace_marker_fd = open("/sys/kernel/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
+        atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
     }
 
     if (atrace_marker_fd == -1) {