From ee3cfca651deae5c8af3e873f5d085074cde9fad Mon Sep 17 00:00:00 2001
From: Tom Madams <tom.ej.madams@gmail.com>
Date: Thu, 6 Jul 2017 15:59:13 -0700
Subject: [PATCH] Fix ThreadCPUUsage when running on RTEMS. (#414)

Change ThreadCPUUsage to call ProcessCPUUsage if __rtems__ is defined.

RTEMS real time OS doesn't support CLOCK_THREAD_CPUTIME_ID. See
https://github.com/RTEMS/rtems/blob/master/cpukit/posix/src/clockgettime.c#L58-L59

Prior to this change, ThreadCPUUsage would fail when running on RTEMS with:
  ERROR: clock_gettime(CLOCK_THREAD_CPUTIME_ID, ...) failed
---
 CONTRIBUTORS          | 1 +
 src/internal_macros.h | 2 ++
 src/timers.cc         | 4 ++++
 3 files changed, 7 insertions(+)

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 58f81fd3..9abb6086 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -51,6 +51,7 @@ Pierre Phaneuf <pphaneuf@google.com>
 Radoslav Yovchev <radoslav.tm@gmail.com>
 Ray Glover <ray.glover@uk.ibm.com>
 Shuo Chen <chenshuo@chenshuo.com>
+Tom Madams <tom.ej.madams@gmail.com> <tmadams@google.com>
 Yixuan Qiu <yixuanq@gmail.com>
 Yusuke Suzuki <utatane.tea@gmail.com>
 Tobias Ulvgård <tobias.ulvgard@dirac.se>
diff --git a/src/internal_macros.h b/src/internal_macros.h
index 8dd9f87b..94288745 100644
--- a/src/internal_macros.h
+++ b/src/internal_macros.h
@@ -45,6 +45,8 @@
 #define BENCHMARK_OS_NACL 1
 #elif defined(EMSCRIPTEN)
 #define BENCHMARK_OS_EMSCRIPTEN 1
+#elif defined(__rtems__)
+#define BENCHMARK_OS_RTEMS 1
 #endif
 
 #if !__has_feature(cxx_exceptions) && !defined(__cpp_exceptions) \
diff --git a/src/timers.cc b/src/timers.cc
index 8d56e8ad..817272d0 100644
--- a/src/timers.cc
+++ b/src/timers.cc
@@ -158,6 +158,10 @@ double ThreadCPUUsage() {
 #elif defined(BENCHMARK_OS_EMSCRIPTEN)
   // Emscripten doesn't support traditional threads
   return ProcessCPUUsage();
+#elif defined(BENCHMARK_OS_RTEMS)
+  // RTEMS doesn't support CLOCK_THREAD_CPUTIME_ID. See
+  // https://github.com/RTEMS/rtems/blob/master/cpukit/posix/src/clockgettime.c
+  return ProcessCPUUsage();
 #elif defined(CLOCK_THREAD_CPUTIME_ID)
   struct timespec ts;
   if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) == 0) return MakeTime(ts);