From 5cdb5d4619e271f4d4f39cc17e7bc6d9d83f22da Mon Sep 17 00:00:00 2001
From: Hridya Valsaraju <hridya@google.com>
Date: Fri, 7 Feb 2020 10:43:12 -0800
Subject: [PATCH] trace-container: Check /sys/kernel/tracing for tracefs

tracefs will be mounted at /sys/kernel/tracing when debugfs
is not mounted.

Bug: 134669095
Test: atest AtraceHostTest
Change-Id: I8178babaa6928ac3796622bdb08f123428ccd191
---
 libcutils/trace-container.cpp | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/libcutils/trace-container.cpp b/libcutils/trace-container.cpp
index c23d5e2bd..f7eed48aa 100644
--- a/libcutils/trace-container.cpp
+++ b/libcutils/trace-container.cpp
@@ -87,24 +87,28 @@ void atrace_set_tracing_enabled(bool enabled)
 
 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 < 0) {
-        // We're in container, ftrace may be disabled. In such case, we use the
-        // socket to write trace event.
+        // try debugfs
+        atrace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_WRONLY | O_CLOEXEC);
+        if (atrace_marker_fd < 0) {
+            // We're in container, ftrace may be disabled. In such case, we use the
+            // socket to write trace event.
 
-        // Protect the initialization of container socket from
-        // atrace_set_tracing_enabled.
-        pthread_mutex_lock(&atrace_enabling_mutex);
-        atrace_use_container_sock = true;
-        bool success = false;
-        if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
-            success = atrace_init_container_sock();
-        }
-        pthread_mutex_unlock(&atrace_enabling_mutex);
+            // Protect the initialization of container socket from
+            // atrace_set_tracing_enabled.
+            pthread_mutex_lock(&atrace_enabling_mutex);
+            atrace_use_container_sock = true;
+            bool success = false;
+            if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
+                success = atrace_init_container_sock();
+            }
+            pthread_mutex_unlock(&atrace_enabling_mutex);
 
-        if (!success) {
-            atrace_enabled_tags = 0;
-            goto done;
+            if (!success) {
+                atrace_enabled_tags = 0;
+                goto done;
+            }
         }
     }
     atrace_enabled_tags = atrace_get_property();