base: Support setting thread priorities generically.

base/threading/platform_thread_linux.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 <sched.h>
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/safe_strerror_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/prctl.h>
+#include <sys/resource.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <unistd.h>
+#endif
+
+namespace base {
+
+namespace {
+int ThreadNiceValue(ThreadPriority priority) {
+  static const int threadPriorityAudio = -10;
+  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::SetName(const char* name) {
+  ThreadIdNameManager::GetInstance()->SetName(CurrentId(), name);
+  tracked_objects::ThreadData::InitializeThreadContext(name);
+
+  // On linux we can get the thread names to show up in the debugger by setting
+  // the process name for the LWP.  We don't want to do this for the main
+  // thread because that would rename the process, causing tools like killall
+  // to stop working.
+  if (PlatformThread::CurrentId() == getpid())
+    return;
+
+  // http://0pointer.de/blog/projects/name-your-threads.html
+  // Set the name for the LWP (which gets truncated to 15 characters).
+  // Note that glibc also has a 'pthread_setname_np' api, but it may not be
+  // available everywhere and it's only benefit over using prctl directly is
+  // that it can set the name of threads other than the current thread.
+  int err = prctl(PR_SET_NAME, name);
+  // We expect EPERM failures in sandboxed processes, just ignore those.
+  if (err < 0 && errno != EPERM)
+    DPLOG(ERROR) << "prctl(PR_SET_NAME)";
+}
+
+// static
+void PlatformThread::SetThreadPriority(PlatformThreadHandle,
+                                       PlatformThreadId id,
+                                       ThreadPriority priority) {
+  // 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;
+}
+
+}  // namespace base