- Add an OSThread structure which is the generic TLS structure for all C++

runtime/vm/thread_registry.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_THREAD_REGISTRY_H_
 #define VM_THREAD_REGISTRY_H_
 
 #include "vm/globals.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/stack_frame.h"
 #include "vm/thread.h"
 
 namespace dart {
 
 // Unordered collection of threads relating to a particular isolate.
 class ThreadRegistry {
  public:
   ThreadRegistry()
       : monitor_(new Monitor()),
-        entries_(),
+        active_list_(NULL),
+        free_list_(NULL),
+        mutator_thread_(NULL),
         in_rendezvous_(false),
         remaining_(0),
         round_(0) {}
 
   ~ThreadRegistry();
 
+  Thread* active_list() const { return active_list_; }
+
   // Bring all threads in this isolate to a safepoint. The caller is
   // expected to be implicitly at a safepoint. The threads will wait
   // until ResumeAllThreads is called. First participates in any
   // already pending rendezvous requested by another thread. Any
   // thread that tries to enter this isolate during rendezvous will
   // wait in RestoreStateTo. Nesting is not supported: the caller must
   // call ResumeAllThreads before making further calls to
   // SafepointThreads.
   void SafepointThreads();
 
   // Unblocks all threads participating in the rendezvous that was organized
   // by a prior call to SafepointThreads.
   // TODO(koda): Consider adding a scope helper to avoid omitting this call.
   void ResumeAllThreads();
 
   // Indicate that the current thread is at a safepoint, and offer to wait for
   // any pending rendezvous request (if none, returns immediately).
   void CheckSafepoint() {
     MonitorLocker ml(monitor_);
     CheckSafepointLocked();
   }
 
-  bool RestoreStateTo(Thread* thread, Thread::State* state,
-                      bool bypass_safepoint) {
-    MonitorLocker ml(monitor_);
-    // Wait for any rendezvous in progress.
-    while (!bypass_safepoint && in_rendezvous_) {
-      ml.Wait(Monitor::kNoTimeout);
-    }
-    Entry* entry = FindEntry(thread);
-    if (entry != NULL) {
-      Thread::State st = entry->state;
-      // TODO(koda): Support same thread re-entering same isolate with
-      // Dart frames in between. For now, just assert it doesn't happen.
-      if (st.top_exit_frame_info != thread->top_exit_frame_info()) {
-        ASSERT(thread->top_exit_frame_info() == 0 ||
-               thread->top_exit_frame_info() > st.top_exit_frame_info);
-      }
-      ASSERT(!entry->scheduled);
-      entry->scheduled = true;
-#if defined(DEBUG)
-      // State field is not in use, so zap it.
-      memset(&entry->state, 0xda, sizeof(entry->state));
-#endif
-      *state = st;
-      return true;
-    }
-    Entry new_entry;
-    new_entry.thread = thread;
-    new_entry.scheduled = true;
-#if defined(DEBUG)
-    // State field is not in use, so zap it.
-    memset(&new_entry.state, 0xda, sizeof(new_entry.state));
-#endif
-    entries_.Add(new_entry);
-    return false;
-  }
-
-  void SaveStateFrom(Thread* thread, const Thread::State& state,
-                     bool bypass_safepoint) {
-    MonitorLocker ml(monitor_);
-    Entry* entry = FindEntry(thread);
-    ASSERT(entry != NULL);
-    ASSERT(entry->scheduled);
-    entry->scheduled = false;
-    entry->state = state;
-    if (!bypass_safepoint && in_rendezvous_) {
-      // Don't wait for this thread.
-      ASSERT(remaining_ > 0);
-      if (--remaining_ == 0) {
-        ml.NotifyAll();
-      }
-    }
-  }
-
-  bool Contains(Thread* thread) {
-    MonitorLocker ml(monitor_);
-    return (FindEntry(thread) != NULL);
-  }
-
-  void CheckNotScheduled(Isolate* isolate) {
-    MonitorLocker ml(monitor_);
-    for (int i = 0; i < entries_.length(); ++i) {
-      const Entry& entry = entries_[i];
-      if (entry.scheduled) {
-        FATAL3("Isolate %p still scheduled on %p (whose isolate_ is %p)\n",
-               isolate,
-               entry.thread,
-               entry.thread->isolate());
-      }
-    }
-  }
-
-  void VisitObjectPointers(ObjectPointerVisitor* visitor,
-                           bool validate_frames) {
-    MonitorLocker ml(monitor_);
-    for (int i = 0; i < entries_.length(); ++i) {
-      const Entry& entry = entries_[i];
-      const Thread::State& state =
-          entry.scheduled ? entry.thread->state_ : entry.state;
-      if (state.zone != NULL) {
-        state.zone->VisitObjectPointers(visitor);
-      }
-      if (entry.scheduled) {
-        ASSERT(entry.thread != NULL);
-        entry.thread->VisitObjectPointers(visitor);
-      }
-      // Iterate over all the stack frames and visit objects on the stack.
-      StackFrameIterator frames_iterator(state.top_exit_frame_info,
-                                         validate_frames);
-      StackFrame* frame = frames_iterator.NextFrame();
-      while (frame != NULL) {
-        frame->VisitObjectPointers(visitor);
-        frame = frames_iterator.NextFrame();
-      }
-    }
-  }
-
-  void PruneThread(Thread* thread);
-
-  void ReclaimTimelineBlocks();
-
-  struct Entry {
-    // NOTE: |thread| is deleted automatically when the thread exits.
-    // In other words, it is not safe to dereference |thread| unless you are on
-    // the thread itself.
-    Thread* thread;
-    bool scheduled;
-    Thread::State state;
-  };
-
-  class EntryIterator {
-   public:
-    explicit EntryIterator(ThreadRegistry* registry);
-    ~EntryIterator();
-
-    // Returns false when there are no more entries.
-    bool HasNext() const;
-
-    // Returns the next entry and moves forward.
-    const Entry& Next();
-
-   private:
-    void Reset(ThreadRegistry* registry);
-
-    intptr_t index_;
-    ThreadRegistry* registry_;
-  };
+  Thread* Schedule(Isolate* isolate, bool is_mutator, bool bypass_safepoint);
+  void Unschedule(Thread* thread, bool is_mutator, bool bypass_safepoint);
+  void VisitObjectPointers(ObjectPointerVisitor* visitor, bool validate_frames);
 
  private:
-  // Returns Entry corresponding to thread in registry or NULL.
-  // Note: Lock should be taken before this function is called.
-  // TODO(koda): Add method Monitor::IsOwnedByCurrentThread.
-  Entry* FindEntry(Thread* thread) {
-    for (int i = 0; i < entries_.length(); ++i) {
-      if (entries_[i].thread == thread) {
-        return &entries_[i];
-      }
-    }
-    return NULL;
-  }
+  Thread* GetThreadFromFreelist(Isolate* isolate);
+  void ReturnThreadToFreelist(Thread* thread);
 
   // Note: Lock should be taken before this function is called.
   void CheckSafepointLocked();
 
   // Returns the number threads that are scheduled on this isolate.
   // Note: Lock should be taken before this function is called.
   intptr_t CountScheduledLocked();
 
   Monitor* monitor_;  // All access is synchronized through this monitor.
-  MallocGrowableArray<Entry> entries_;
+  Thread* active_list_;  // List of active threads in the isolate.
+  Thread* free_list_;  // Free list of Thread objects that can be reused.
+  // TODO(asiva): Currently we treat a mutator thread as a special thread
+  // and always schedule execution of Dart code on the same mutator thread
+  // object. This is because ApiState is still an object associated with
+  // the isolate and switching execution to another thread causes problems.
+  // Once ApiState is made a per Thread object it should be possible to
+  // free a mutator thread like all other threads and continue running on
+  // a different thread.
+  Thread* mutator_thread_;
 
   // Safepoint rendezvous state.
   bool in_rendezvous_;    // A safepoint rendezvous request is in progress.
   intptr_t remaining_;    // Number of threads yet to reach their safepoint.
   int64_t round_;         // Counter, to prevent missing updates to remaining_
                           // (see comments in CheckSafepointLocked).
 
   DISALLOW_COPY_AND_ASSIGN(ThreadRegistry);
 };
 
 }  // namespace dart
 
 #endif  // VM_THREAD_REGISTRY_H_