Add full SetThreadPriority support to Windows.

base/threading/platform_thread_posix.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 <pthread.h>
 #include <sched.h>
 #include <sys/resource.h>
 #include <sys/time.h>
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/safe_strerror_posix.h"
+#include "base/scoped_clear_errno.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread_internal_posix.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/tracked_objects.h"
 
 #if defined(OS_LINUX)
 #include <sys/syscall.h>
 #elif defined(OS_ANDROID)
 #include <sys/types.h>
@@ skipping 198 matching lines @@
 
 // static
 void PlatformThread::Join(PlatformThreadHandle thread_handle) {
   // Joining another thread may block the current thread for a long time, since
   // the thread referred to by |thread_handle| may still be running long-lived /
   // blocking tasks.
   base::ThreadRestrictions::AssertIOAllowed();
   CHECK_EQ(0, pthread_join(thread_handle.handle_, NULL));
 }
 
-// Mac has its own SetThreadPriority() implementation.
+// Mac has its own Set/GetThreadPriority() implementations.
 #if !defined(OS_MACOSX)
+
 // static
 void PlatformThread::SetThreadPriority(PlatformThreadHandle handle,
                                        ThreadPriority priority) {
-#if !defined(OS_NACL)
+#if defined(OS_NACL)
+  NOTIMPLEMENTED();
+#else
   if (internal::HandleSetThreadPriorityForPlatform(handle, priority))
     return;
 
   // setpriority(2) should change the whole thread group's (i.e. process)
   // priority. However, as stated in the bugs section of
   // http://man7.org/linux/man-pages/man2/getpriority.2.html: "under the current
   // Linux/NPTL implementation of POSIX threads, the nice value is a per-thread
   // attribute". Also, 0 is prefered to the current thread id since it is
   // equivalent but makes sandboxing easier (https://crbug.com/399473).
   DCHECK_NE(handle.id_, kInvalidThreadId);
   const int nice_setting = internal::ThreadPriorityToNiceValue(priority);
   const PlatformThreadId current_id = PlatformThread::CurrentId();
   if (setpriority(PRIO_PROCESS, handle.id_ == current_id ? 0 : handle.id_,
                   nice_setting)) {
     DVPLOG(1) << "Failed to set nice value of thread (" << handle.id_ << ") to "
               << nice_setting;
   }
+#endif  // defined(OS_NACL)
+}
+
+// static
+ThreadPriority PlatformThread::GetThreadPriority(PlatformThreadHandle handle) {
+#if defined(OS_NACL)
+  NOTIMPLEMENTED();
+  return kThreadPriority_Normal;
+#else
+  // Mirrors SetThreadPriority()'s implementation.
+  ThreadPriority platform_specific_priority;
+  if (internal::HandleGetThreadPriorityForPlatform(
+          handle, &platform_specific_priority)) {
+    return platform_specific_priority;
+  }
+
+  DCHECK_NE(handle.id_, kInvalidThreadId);
+  const PlatformThreadId current_id = PlatformThread::CurrentId();
+  // Need to clear errno before calling getpriority():
+  // http://man7.org/linux/man-pages/man2/getpriority.2.html
+  ScopedClearErrno clear_errno;

[rvargas (doing something else), 2015/03/19 22:19:21]

errno = 0 instead?

[gab, 2015/03/30 20:14:45]

I don't know much about Chromium POSIX development, assumed that it was perhaps
prefered not to clobber errno here as a base/ citizen, but I don't care either
way, up to you.

[rvargas (doing something else), 2015/03/30 22:31:22]

There is no contract on base to preserve errno (or last error). All that the API
you're calling requires is for it to be zero beforehand.

[gab, 2015/03/31 14:02:33]

Done.

+  int nice_value =
+      getpriority(PRIO_PROCESS, handle.id_ == current_id ? 0 : handle.id_);
+  if (errno != 0) {
+    DVPLOG(1) << "Failed to get nice value of thread (" << handle.id_ << ")";
+    return kThreadPriority_Normal;
+  }
+
+  return internal::NiceValueToThreadPriority(nice_value);
 #endif  // !defined(OS_NACL)
 }
+
 #endif  // !defined(OS_MACOSX)
 
 }  // namespace base