Have content/ create and destroy its own threads.

content/browser/browser_thread_impl.cc

 // Copyright (c) 2011 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 "content/browser/browser_thread_impl.h"
 
+#include "base/atomicops.h"
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/message_loop.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/thread_restrictions.h"
 
+namespace content {
+
 namespace {
 
 // Friendly names for the well-known threads.
-static const char* browser_thread_names[content::BrowserThread::ID_COUNT] = {
+static const char* g_browser_thread_names[BrowserThread::ID_COUNT] = {
   "",  // UI (name assembled in browser_main.cc).
   "Chrome_DBThread",  // DB
   "Chrome_WebKitThread",  // WEBKIT
   "Chrome_FileThread",  // FILE
   "Chrome_ProcessLauncherThread",  // PROCESS_LAUNCHER
   "Chrome_CacheThread",  // CACHE
   "Chrome_IOThread",  // IO
 #if defined(OS_CHROMEOS)
   "Chrome_WebSocketproxyThread",  // WEB_SOCKET_PROXY
 #endif
 };
 
-}  // namespace
-
-namespace content {
-
-namespace {
-
-// This lock protects |g_browser_threads|.  Do not read or modify that array
-// without holding this lock.  Do not block while holding this lock.
+// This lock protects |g_browser_threads|.  Do not read or modify that
+// array without holding this lock.  Do not block while holding this
+// lock.
 base::LazyInstance<base::Lock,
                    base::LeakyLazyInstanceTraits<base::Lock> >
     g_lock = LAZY_INSTANCE_INITIALIZER;
 
+// This array is protected by |g_lock|.  The threads are not owned by this
+// array. Typically, the threads are owned on the UI thread by
+// content::BrowserMainLoop.  BrowserThreadImpl objects remove
+// themselves from this array upon destruction.
+static BrowserThreadImpl* g_browser_threads[BrowserThread::ID_COUNT];
 
-// An array of the BrowserThread objects.  This array is protected by |g_lock|.
-// The threads are not owned by this array.  Typically, the threads are owned
-// on the UI thread by the g_browser_process object.  BrowserThreads remove
-// themselves from this array upon destruction.
-BrowserThread* g_browser_threads[BrowserThread::ID_COUNT];
+// Only atomic operations are used on this array.  The delegates are
+// not owned by this array, rather by whoever calls
+// BrowserThread::SetDelegate.
+static BrowserThreadDelegate* g_browser_thread_delegates[
+    BrowserThread::ID_COUNT];
 
 }  // namespace
 
-BrowserThreadImpl::BrowserThreadImpl(BrowserThread::ID identifier)
-    : BrowserThread(identifier) {
+BrowserThreadImpl::BrowserThreadImpl(ID identifier)
+    : Thread(g_browser_thread_names[identifier]),
+      identifier_(identifier) {
+  Initialize();
 }
 
-BrowserThreadImpl::BrowserThreadImpl(BrowserThread::ID identifier,
+BrowserThreadImpl::BrowserThreadImpl(ID identifier,
                                      MessageLoop* message_loop)
-    : BrowserThread(identifier, message_loop) {
+    : Thread(message_loop->thread_name().c_str()),
+      identifier_(identifier) {
+  set_message_loop(message_loop);
+  Initialize();
+}
+
+void BrowserThreadImpl::Init() {
+  using base::subtle::AtomicWord;
+  AtomicWord* storage =
+      reinterpret_cast<AtomicWord*>(&g_browser_thread_delegates[identifier_]);
+  AtomicWord stored_pointer = base::subtle::NoBarrier_Load(storage);
+  BrowserThreadDelegate* delegate =
+      reinterpret_cast<BrowserThreadDelegate*>(stored_pointer);
+  if (delegate)
+    delegate->Init();
+}
+
+void BrowserThreadImpl::CleanUp() {
+  using base::subtle::AtomicWord;
+  AtomicWord* storage =
+      reinterpret_cast<AtomicWord*>(&g_browser_thread_delegates[identifier_]);
+  AtomicWord stored_pointer = base::subtle::NoBarrier_Load(storage);
+  BrowserThreadDelegate* delegate =
+      reinterpret_cast<BrowserThreadDelegate*>(stored_pointer);
+
+  // Note that we could remove the delegate pointer from
+  // g_browser_thread_delegates after calling CleanUp on it, but this
+  // would defeat the DCHECK in SetDelegate below that checks if a
+  // delegate was previously registered for the thread.
+  if (delegate)
+    delegate->CleanUp();
+}
+
+void BrowserThreadImpl::Initialize() {
+  base::AutoLock lock(g_lock.Get());
+  DCHECK(identifier_ >= 0 && identifier_ < ID_COUNT);
+  DCHECK(g_browser_threads[identifier_] == NULL);
+  g_browser_threads[identifier_] = this;
 }
 
 BrowserThreadImpl::~BrowserThreadImpl() {
+  // All Thread subclasses must call Stop() in the destructor. This is
+  // doubly important here as various bits of code check they are on
+  // the right BrowserThread.
   Stop();
+
+  base::AutoLock lock(g_lock.Get());
+  g_browser_threads[identifier_] = NULL;
+#ifndef NDEBUG
+  // Double check that the threads are ordered correctly in the enumeration.
+  for (int i = identifier_ + 1; i < ID_COUNT; ++i) {
+    DCHECK(!g_browser_threads[i]) <<
+        "Threads must be listed in the reverse order that they die";
+  }
+#endif
 }
 
 // static
 bool BrowserThreadImpl::PostTaskHelper(
     BrowserThread::ID identifier,
     const tracked_objects::Location& from_here,
     Task* task,
     int64 delay_ms,
     bool nestable) {
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
   // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
   // order of lifetime.  So no need to lock if we know that the other thread
   // outlives this one.
   // Note: since the array is so small, ok to loop instead of creating a map,
   // which would require a lock because std::map isn't thread safe, defeating
   // the whole purpose of this optimization.
   BrowserThread::ID current_thread;
   bool guaranteed_to_outlive_target_thread =
       GetCurrentThreadIdentifier(&current_thread) &&
-      current_thread >= identifier;
+      current_thread <= identifier;
 
   if (!guaranteed_to_outlive_target_thread)
     g_lock.Get().Acquire();
 
   MessageLoop* message_loop = g_browser_threads[identifier] ?
       g_browser_threads[identifier]->message_loop() : NULL;
   if (message_loop) {
     if (nestable) {
       message_loop->PostDelayedTask(from_here, task, delay_ms);
     } else {
@@ skipping 20 matching lines @@
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
   // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
   // order of lifetime.  So no need to lock if we know that the other thread
   // outlives this one.
   // Note: since the array is so small, ok to loop instead of creating a map,
   // which would require a lock because std::map isn't thread safe, defeating
   // the whole purpose of this optimization.
   BrowserThread::ID current_thread;
   bool guaranteed_to_outlive_target_thread =
       GetCurrentThreadIdentifier(&current_thread) &&
-      current_thread >= identifier;
+      current_thread <= identifier;
 
   if (!guaranteed_to_outlive_target_thread)
     g_lock.Get().Acquire();
 
   MessageLoop* message_loop = g_browser_threads[identifier] ?
       g_browser_threads[identifier]->message_loop() : NULL;
   if (message_loop) {
     if (nestable) {
       message_loop->PostDelayedTask(from_here, task, delay_ms);
     } else {
       message_loop->PostNonNestableDelayedTask(from_here, task, delay_ms);
     }
   }
 
   if (!guaranteed_to_outlive_target_thread)
     g_lock.Get().Release();
 
   return !!message_loop;
 }
 
-// TODO(joi): Remove
-DeprecatedBrowserThread::DeprecatedBrowserThread(BrowserThread::ID identifier)
-    : BrowserThread(identifier) {
-}
-DeprecatedBrowserThread::DeprecatedBrowserThread(BrowserThread::ID identifier,
-                                                 MessageLoop* message_loop)
-    : BrowserThread(identifier, message_loop) {
-}
-DeprecatedBrowserThread::~DeprecatedBrowserThread() {
-  Stop();
-}
-
 // An implementation of MessageLoopProxy to be used in conjunction
 // with BrowserThread.
 class BrowserThreadMessageLoopProxy : public base::MessageLoopProxy {
  public:
   explicit BrowserThreadMessageLoopProxy(BrowserThread::ID identifier)
       : id_(identifier) {
   }
 
   // MessageLoopProxy implementation.
   virtual bool PostTask(const tracked_objects::Location& from_here,
@@ skipping 44 matching lines @@
 
   virtual bool BelongsToCurrentThread() {
     return BrowserThread::CurrentlyOn(id_);
   }
 
  private:
   BrowserThread::ID id_;
   DISALLOW_COPY_AND_ASSIGN(BrowserThreadMessageLoopProxy);
 };
 
-BrowserThread::BrowserThread(ID identifier)
-    : Thread(browser_thread_names[identifier]),
-      identifier_(identifier) {
-  Initialize();
-}
-
-BrowserThread::BrowserThread(ID identifier,
-                             MessageLoop* message_loop)
-    : Thread(message_loop->thread_name().c_str()),
-      identifier_(identifier) {
-  set_message_loop(message_loop);
-  Initialize();
-}
-
-void BrowserThread::Initialize() {
-  base::AutoLock lock(g_lock.Get());
-  DCHECK(identifier_ >= 0 && identifier_ < ID_COUNT);
-  DCHECK(g_browser_threads[identifier_] == NULL);
-  g_browser_threads[identifier_] = this;
-}
-
-BrowserThread::~BrowserThread() {
-  // Stop the thread here, instead of the parent's class destructor.  This is so
-  // that if there are pending tasks that run, code that checks that it's on the
-  // correct BrowserThread succeeds.
-  Stop();
-
-  base::AutoLock lock(g_lock.Get());
-  g_browser_threads[identifier_] = NULL;
-#ifndef NDEBUG
-  // Double check that the threads are ordered correctly in the enumeration.
-  for (int i = identifier_ + 1; i < ID_COUNT; ++i) {
-    DCHECK(!g_browser_threads[i]) <<
-        "Threads must be listed in the reverse order that they die";
-  }
-#endif
-}
-
 // static
 bool BrowserThread::IsWellKnownThread(ID identifier) {
   base::AutoLock lock(g_lock.Get());
   return (identifier >= 0 && identifier < ID_COUNT &&
           g_browser_threads[identifier]);
 }
 
 // static
 bool BrowserThread::CurrentlyOn(ID identifier) {
   // We shouldn't use MessageLoop::current() since it uses LazyInstance which
@@ skipping 120 matching lines @@
 
 // static
 scoped_refptr<base::MessageLoopProxy>
 BrowserThread::GetMessageLoopProxyForThread(
     ID identifier) {
   scoped_refptr<base::MessageLoopProxy> proxy(
       new BrowserThreadMessageLoopProxy(identifier));
   return proxy;
 }
 
+base::Thread* BrowserThread::UnsafeGetBrowserThread(ID identifier) {
+  base::AutoLock lock(g_lock.Get());
+  base::Thread* thread = g_browser_threads[identifier];
+  DCHECK(thread);
+  return thread;
+}
+
+void BrowserThread::SetDelegate(ID identifier,
+                                BrowserThreadDelegate* delegate) {
+  DCHECK(delegate);
+
+  using base::subtle::AtomicWord;
+  AtomicWord* storage = reinterpret_cast<AtomicWord*>(
+      &g_browser_thread_delegates[identifier]);
+  AtomicWord old_pointer = base::subtle::NoBarrier_AtomicExchange(
+      storage, reinterpret_cast<AtomicWord>(delegate));
+
+  // This catches registration when previously registered.
+  DCHECK(!old_pointer);
+}
+
 }  // namespace content