Fix thread names for android traces

Summary: Collecting traces from Android devices do not correctly show thread names for threads manually created outside of the JVM.   This change will correctly set the Java thread name to match the posix thread name.

Reviewed By: dreiss

Differential Revision: D20293251

fbshipit-source-id: 35b95c653ff1fd79e339dd2a854be8aaaa604ce2

first-party/fbjni/cxx/fbjni/detail/Environment.cpp

@@ -16,6 +16,10 @@
 
 #include <fbjni/fbjni.h>
 
+#ifdef __ANDROID__
+#include <sys/prctl.h>
+#endif // __ANDROID__
+
 #include <functional>
 #ifndef _WIN32
 #include <pthread.h>
@@ -65,8 +69,33 @@ struct AttachTraits<jint(JavaVM::*)(void**, void*)> {
   using EnvType = void*;
 };
 
+std::string getThreadName() {
+#ifdef _WIN32
+  return "";
+#else // _WIN32
+  constexpr int kMaxThreadNameSize = 100;
+  int ret = 0;
+  char threadName[kMaxThreadNameSize];
+#ifdef __ANDROID__
+  ret = prctl(PR_GET_NAME, threadName);
+#else
+  ret = pthread_getname_np(pthread_self(), threadName, sizeof(threadName));
+#endif
+  if (ret != 0) {
+    return "";
+  }
+  return threadName;
+#endif // _WIN32
+}
+
 JNIEnv* attachCurrentThread() {
   JavaVMAttachArgs args{JNI_VERSION_1_6, nullptr, nullptr};
+
+  const auto threadName = getThreadName();
+  if (threadName.size()) {
+    args.name = threadName.c_str();
+  }
+
   using AttachEnvType =
       typename AttachTraits<decltype(&JavaVM::AttachCurrentThread)>::EnvType;
   AttachEnvType env;