Add full SetThreadPriority support to Windows.

base/threading/platform_thread_posix.cc

Index: base/threading/platform_thread_posix.cc
diff --git a/base/threading/platform_thread_posix.cc b/base/threading/platform_thread_posix.cc
index 5c5023b1c27a996b2b4c617653d7bbefd57ca904..7b20b854e6c277c287ea7defa42274041243460a 100644
--- a/base/threading/platform_thread_posix.cc
+++ b/base/threading/platform_thread_posix.cc
@@ -14,6 +14,7 @@
 #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"
@@ -232,12 +233,15 @@ void PlatformThread::Join(PlatformThreadHandle thread_handle) {
   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;
 
@@ -255,8 +259,38 @@ void PlatformThread::SetThreadPriority(PlatformThreadHandle handle,
     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