base: Implement GetCurrentThreadPriority.

base/threading/platform_thread_mac.mm

 // 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"
 
 #import <Foundation/Foundation.h>
 #include <mach/mach.h>
 #include <mach/mach_time.h>
 #include <mach/thread_policy.h>
 #include <stddef.h>
 #include <sys/resource.h>
 
 #include <algorithm>
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/mac/foundation_util.h"
 #include "base/mac/mach_logging.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/tracked_objects.h"
 #include "build/build_config.h"
 
 namespace base {
 
+namespace {
+NSString* const kThreadPriorityKey = @"CrThreadPriorityKey";
+}  // namespace
+
 // If Cocoa is to be used on more than one thread, it must know that the
 // application is multithreaded.  Since it's possible to enter Cocoa code
 // from threads created by pthread_thread_create, Cocoa won't necessarily
 // be aware that the application is multithreaded.  Spawning an NSThread is
 // enough to get Cocoa to set up for multithreaded operation, so this is done
 // if necessary before pthread_thread_create spawns any threads.
 //
 // http://developer.apple.com/documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/chapter_4_section_4.html
 void InitThreading() {
   static BOOL multithreaded = [NSThread isMultiThreaded];
@@ skipping 122 matching lines @@
 }  // anonymous namespace
 
 // static
 void PlatformThread::SetCurrentThreadPriority(ThreadPriority priority) {
   // Convert from pthread_t to mach thread identifier.
   mach_port_t mach_thread_id =
       pthread_mach_thread_np(PlatformThread::CurrentHandle().platform_handle());
 
   switch (priority) {
     case ThreadPriority::NORMAL:
+    case ThreadPriority::BACKGROUND:
+    case ThreadPriority::DISPLAY:
+      // Add support for non-NORMAL thread priorities. https://crbug.com/554651
       SetPriorityNormal(mach_thread_id);
       break;
     case ThreadPriority::REALTIME_AUDIO:
       SetPriorityRealtimeAudio(mach_thread_id);
       break;
-    default:
-      NOTREACHED() << "Unknown priority.";
-      break;
   }
+
+  [[[NSThread currentThread] threadDictionary]
+      setObject:@(static_cast<int>(priority))
+         forKey:kThreadPriorityKey];
 }
 
 // static
 ThreadPriority PlatformThread::GetCurrentThreadPriority() {
-  NOTIMPLEMENTED();
-  return ThreadPriority::NORMAL;
+  NSNumber* priority = base::mac::ObjCCast<NSNumber>([[[NSThread currentThread]
+      threadDictionary] objectForKey:kThreadPriorityKey]);
+
+  if (!priority)
+    return ThreadPriority::NORMAL;
+
+  ThreadPriority thread_priority =
+      static_cast<ThreadPriority>(priority.intValue);
+  switch (thread_priority) {
+    case ThreadPriority::BACKGROUND:
+    case ThreadPriority::NORMAL:
+    case ThreadPriority::DISPLAY:
+    case ThreadPriority::REALTIME_AUDIO:
+      return thread_priority;
+    default:
+      NOTREACHED() << "Unknown priority.";
+      return ThreadPriority::NORMAL;

[gab, 2016/03/15 02:37:07]

nit: Prefer putting these two lines outside the switch statement and removing
the "default" statement. That way if a new ThreadPriority is added, clang will
throw an error when compiling the switch instead of silently providing an
undesired implementation.

+  }
 }
 
 size_t GetDefaultThreadStackSize(const pthread_attr_t& attributes) {
 #if defined(OS_IOS)
   return 0;
 #else
   // The Mac OS X default for a pthread stack size is 512kB.
   // Libc-594.1.4/pthreads/pthread.c's pthread_attr_init uses
   // DEFAULT_STACK_SIZE for this purpose.
   //
@@ skipping 21 matching lines @@
                  static_cast<size_t>(stack_rlimit.rlim_cur));
   }
   return default_stack_size;
 #endif
 }
 
 void TerminateOnThread() {
 }
 
 }  // namespace base