base: Support setting thread priorities generically.

base/threading/platform_thread_android.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/threading/platform_thread.h"
+
+#include <errno.h>
+#include <sys/resource.h>
+
+#include "base/android/jni_android.h"
+#include "base/android/thread_utils.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "jni/ThreadUtils_jni.h"
+
+namespace base {
+
+namespace {
+int ThreadNiceValue(ThreadPriority priority) {
+  // These nice values are taken from Android, which uses nice
+  // values like linux, but defines some preset nice values.
+  //   Process.THREAD_PRIORITY_AUDIO = -16
+  //   Process.THREAD_PRIORITY_BACKGROUND = 10
+  //   Process.THREAD_PRIORITY_DEFAULT = 0;
+  //   Process.THREAD_PRIORITY_DISPLAY = -4;
+  //   Process.THREAD_PRIORITY_FOREGROUND = -2;
+  //   Process.THREAD_PRIORITY_LESS_FAVORABLE = 1;
+  //   Process.THREAD_PRIORITY_LOWEST = 19;
+  //   Process.THREAD_PRIORITY_MORE_FAVORABLE = -1;
+  //   Process.THREAD_PRIORITY_URGENT_AUDIO = -19;
+  //   Process.THREAD_PRIORITY_URGENT_DISPLAY = -8;
+  // We use -6 for display, but we may want to split this
+  // into urgent (-8) and non-urgent (-4).
+  static const int threadPriorityAudio = -16;
+  static const int threadPriorityBackground = 10;
+  static const int threadPriorityDefault = 0;
+  static const int threadPriorityDisplay = -6;
+  switch (priority) {
+    case kThreadPriority_RealtimeAudio:
+      return threadPriorityAudio;
+    case kThreadPriority_Background:
+      return threadPriorityBackground;
+    case kThreadPriority_Normal:
+      return threadPriorityDefault;
+    case kThreadPriority_Display:
+      return threadPriorityDisplay;
+    default:
+      NOTREACHED() << "Unknown priority.";
+      return 0;
+  }
+}
+} // namespace
+
+//static
+void PlatformThread::SetThreadPriority(PlatformThreadHandle,
+                                       PlatformThreadId id,
+                                       ThreadPriority priority) {
+  // On Android, we set the Audio priority through JNI as Audio priority
+  // will also allow the process to run while it is backgrounded.
+  if (priority == kThreadPriority_RealtimeAudio) {
+    JNIEnv* env = base::android::AttachCurrentThread();
+    Java_ThreadUtils_setThreadPriorityAudio(env, PlatformThread::CurrentId());
+    return;
+  }
+
+  // setpriority(2) will set a thread's priority if it is passed a tid as
+  // the 'process identifier', not affecting the rest of the threads in the
+  // process. Setting this priority will only succeed if the user has been
+  // granted permission to adjust nice values on the system.
+  DCHECK_NE(id, kInvalidThreadId);
+  int kNiceSetting = ThreadNiceValue(priority);
+  if (setpriority(PRIO_PROCESS, id, kNiceSetting))
+    LOG(ERROR) << "Failed to set nice value of thread to " << kNiceSetting;
+}
+
+void InitOnThread() {
+  // Threads on linux/android may inherit their priority from the thread
+  // where they were created. This sets all new threads to the default.
+  PlatformThread::SetThreadPriority(pthread_self(),
+                                    PlatformThread::CurrentId(),
+                                    kThreadPriority_Normal);
+}
+
+void TerminateOnThread() {
+  base::android::DetachFromVM();
+}
+
+bool RegisterThreadUtils(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+}  // namespace base