Refactor Thread lifecycle interface, add Thread::Enter/ExitIsolate.

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
===================================================================
--- runtime/vm/thread.cc	(revision 44762)
+++ runtime/vm/thread.cc	(working copy)
@@ -6,6 +6,8 @@
 
 #include "vm/isolate.h"
 #include "vm/os_thread.h"
+#include "vm/profiler.h"
+#include "vm/thread_interrupter.h"
 
 
 namespace dart {
@@ -27,4 +29,62 @@
   OSThread::SetThreadLocal(thread_key_, reinterpret_cast<uword>(current));
 }
 
+
+void Thread::EnsureInit() {
+  if (Thread::Current() == NULL) {
+    SetCurrent(new Thread());
+  }
+}
+
+
+void Thread::CleanUp() {
+  // We currently deallocate the Thread, to ensure that embedder threads don't
+  // leak the Thread structure. An alternative approach would be to clear and
+  // reuse it, but register a destructor at the OS level.
+  Thread* current = Current();
+  if (current != NULL) {
+    delete current;
+  }
+  SetCurrent(NULL);
+}
+
+
+void Thread::EnterIsolate(Isolate* isolate) {
+  EnsureInit();
+  Thread* thread = Thread::Current();
+  ASSERT(thread->isolate() == NULL);
+  ASSERT(isolate->mutator_thread() == NULL);
+  isolate->set_mutator_thread(thread);
+  // TODO(koda): Migrate thread_state_ and profile_data_ to Thread, to allow
+  // helper threads concurrent with mutator.
+  ASSERT(isolate->thread_state() == NULL);
+  InterruptableThreadState* thread_state =
+      ThreadInterrupter::GetCurrentThreadState();
+#if defined(DEBUG)
+  Isolate::CheckForDuplicateThreadState(thread_state);
+#endif
+  ASSERT(thread_state != NULL);
+  Profiler::BeginExecution(isolate);
+  isolate->set_thread_state(thread_state);
+  isolate->set_vm_tag(VMTag::kVMTagId);
+  thread->isolate_ = isolate;
+}
+
+
+void Thread::ExitIsolate() {
+  Thread* thread = Thread::Current();
+  // TODO(koda): Audit callers; they should know whether they're in an isolate.
+  if (thread == NULL) return;
+  Isolate* isolate = thread->isolate();
+  ASSERT(isolate != NULL);
+  isolate->set_vm_tag(VMTag::kIdleTagId);
+  isolate->set_thread_state(NULL);
+  Profiler::EndExecution(isolate);
+  isolate->set_mutator_thread(NULL);
+  thread->isolate_ = NULL;
+  ASSERT(Isolate::Current() == NULL);
+  CleanUp();
+}
+
+
 }  // namespace dart