chromium/base: Port thread support to OS/2.

Needed for #3.

chromium/base/BUILD.gn

@@ -839,6 +839,7 @@ jumbo_component("base") {
     "threading/platform_thread_android.cc",
     "threading/platform_thread_linux.cc",
     "threading/platform_thread_mac.mm",
+    "threading/platform_thread_os2.cc",
     "threading/platform_thread_win.cc",
     "threading/platform_thread_win.h",
     "threading/post_task_and_reply_impl.cc",
@@ -1870,7 +1871,7 @@ jumbo_component("base") {
     ]
   }
 
-  if (is_posix && !is_mac && !is_ios && !is_nacl) {
+  if (is_posix && !is_mac && !is_ios && !is_nacl && !is_os2) {
     sources += [
       "posix/can_lower_nice_to.cc",
       "posix/can_lower_nice_to.h",

chromium/base/threading/platform_thread_internal_posix.h

@@ -32,6 +32,7 @@ int ThreadPriorityToNiceValue(ThreadPriority priority);
 // specific implementation of kThreadPriorityToNiceValueMap.
 BASE_EXPORT ThreadPriority NiceValueToThreadPriority(int nice_value);
 
+#if !defined(OS_OS2)
 // If non-nullopt, this return value will be used as the platform-specific
 // result of CanIncreaseThreadPriority().
 Optional<bool> CanIncreaseCurrentThreadPriorityForPlatform(
@@ -46,6 +47,7 @@ bool SetCurrentThreadPriorityForPlatform(ThreadPriority priority);
 // If non-null, this return value will be used as the platform-specific result
 // of CanIncreaseThreadPriority().
 Optional<ThreadPriority> GetCurrentThreadPriorityForPlatform();
+#endif
 
 #if defined(OS_LINUX)
 // Current thread id is cached in thread local storage for performance reasons.

chromium/base/threading/platform_thread_os2.cc

@@ -0,0 +1,38 @@
+// Copyright 2020 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 "base/threading/platform_thread_internal_posix.h"
+#include "base/threading/thread_id_name_manager.h"
+
+namespace base {
+
+namespace internal {
+
+// kLIBC maps nice values to OS/2 priorities in __libc_back_priorityOS2FromUnix,
+// consult it for details.
+const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
+    {ThreadPriority::BACKGROUND, 20}, // PRTYC_IDLETIME + 0
+    {ThreadPriority::NORMAL, 0}, // PRTYC_REGULAR + 0
+    {ThreadPriority::DISPLAY, -10}, // PRTYC_FOREGROUNDSERVER + 0
+    {ThreadPriority::REALTIME_AUDIO, -18}, // PRTYC_TIMECRITICAL + 0
+};
+
+}  // namespace internal
+
+void InitThreading() {}
+
+void TerminateOnThread() {}
+
+size_t GetDefaultThreadStackSize(const pthread_attr_t& attributes) {
+  return 0;
+}
+
+// static
+void PlatformThread::SetName(const std::string& name) {
+  ThreadIdNameManager::GetInstance()->SetName(name);
+}
+
+}  // namespace base

chromium/base/threading/platform_thread_posix.cc

@@ -6,7 +6,9 @@
 
 #include <errno.h>
 #include <pthread.h>
+#if !defined(OS_OS2)
 #include <sched.h>
+#endif
 #include <stddef.h>
 #include <stdint.h>
 #include <sys/time.h>
@@ -216,7 +218,12 @@ PlatformThreadHandle PlatformThread::CurrentHandle() {
 
 // static
 void PlatformThread::YieldCurrentThread() {
+#if defined(OS_OS2)
+  // Under OS/2 this will end up in DosSleep(0) which does yielding.
+  pthread_yield();
+#else
   sched_yield();
+#endif
 }
 
 // static
@@ -290,6 +297,8 @@ void PlatformThread::Detach(PlatformThreadHandle thread_handle) {
 bool PlatformThread::CanIncreaseThreadPriority(ThreadPriority priority) {
 #if defined(OS_NACL)
   return false;
+#elif defined(OS_OS2)
+  return true;
 #else
   auto platform_specific_ability =
       internal::CanIncreaseCurrentThreadPriorityForPlatform(priority);
@@ -306,8 +315,10 @@ void PlatformThread::SetCurrentThreadPriorityImpl(ThreadPriority priority) {
 #if defined(OS_NACL)
   NOTIMPLEMENTED();
 #else
+#if !defined(OS_OS2)
   if (internal::SetCurrentThreadPriorityForPlatform(priority))
     return;
+#endif
 
   // setpriority(2) should change the whole thread group's (i.e. process)
   // priority. However, as stated in the bugs section of
@@ -329,11 +340,13 @@ ThreadPriority PlatformThread::GetCurrentThreadPriority() {
   NOTIMPLEMENTED();
   return ThreadPriority::NORMAL;
 #else
+#if !defined(OS_OS2)
   // Mirrors SetCurrentThreadPriority()'s implementation.
   auto platform_specific_priority =
       internal::GetCurrentThreadPriorityForPlatform();
   if (platform_specific_priority)
     return platform_specific_priority.value();
+#endif
 
   // Need to clear errno before calling getpriority():
   // http://man7.org/linux/man-pages/man2/getpriority.2.html
@@ -353,9 +366,13 @@ ThreadPriority PlatformThread::GetCurrentThreadPriority() {
 
 // static
 size_t PlatformThread::GetDefaultThreadStackSize() {
+#if !defined(OS_OS2)
   pthread_attr_t attributes;
   pthread_attr_init(&attributes);
   return base::GetDefaultThreadStackSize(attributes);
+#else
+  return 0;
+#endif
 }
 
 }  // namespace base