xpcom/threads/nsThreadManager.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* ***** BEGIN LICENSE BLOCK *****
   4  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   5  *
   6  * The contents of this file are subject to the Mozilla Public License Version
   7  * 1.1 (the "License"); you may not use this file except in compliance with
   8  * the License. You may obtain a copy of the License at
   9  * http://www.mozilla.org/MPL/
  10  *
  11  * Software distributed under the License is distributed on an "AS IS" basis,
  12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  13  * for the specific language governing rights and limitations under the
  14  * License.
  15  *
  16  * The Original Code is Mozilla code.
  17  *
  18  * The Initial Developer of the Original Code is Google Inc.
  19  * Portions created by the Initial Developer are Copyright (C) 2006
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *  Darin Fisher <darin@meer.net>
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #include "nsThreadManager.h"
  40 #include "nsThread.h"
  41 #include "nsThreadUtils.h"
  42 #include "nsIClassInfoImpl.h"
  43 #include "nsTArray.h"
  44 #include "nsAutoPtr.h"
  45 #include "nsAutoLock.h"
  46
  47 #ifdef XP_WIN
  48 #include <windows.h>
  49 DWORD gTLSIsMainThreadIndex = TlsAlloc();
  50 #elif defined(NS_TLS)
  51 NS_TLS bool gTLSIsMainThread = false;
  52 #endif
  53
  54 typedef nsTArray< nsRefPtr<nsThread> > nsThreadArray;
  55
  56 //-----------------------------------------------------------------------------
  57
  58 static void
  59 ReleaseObject(void *data)
  60 {
  61   static_cast<nsISupports *>(data)->Release();
  62 }
  63
  64 static PLDHashOperator
  65 AppendAndRemoveThread(const void *key, nsRefPtr<nsThread> &thread, void *arg)
  66 {
  67   nsThreadArray *threads = static_cast<nsThreadArray *>(arg);
  68   threads->AppendElement(thread);
  69   return PL_DHASH_REMOVE;
  70 }
  71
  72 //-----------------------------------------------------------------------------
  73
  74 nsThreadManager nsThreadManager::sInstance;
  75
  76 // statically allocated instance
  77 NS_IMETHODIMP_(nsrefcnt) nsThreadManager::AddRef() { return 2; }
  78 NS_IMETHODIMP_(nsrefcnt) nsThreadManager::Release() { return 1; }
  79 NS_IMPL_CLASSINFO(nsThreadManager, NULL,
  80                   nsIClassInfo::THREADSAFE | nsIClassInfo::SINGLETON,
  81                   NS_THREADMANAGER_CID)
  82 NS_IMPL_QUERY_INTERFACE1_CI(nsThreadManager, nsIThreadManager)
  83 NS_IMPL_CI_INTERFACE_GETTER1(nsThreadManager, nsIThreadManager)
  84
  85 //-----------------------------------------------------------------------------
  86
  87 nsresult
  88 nsThreadManager::Init()
  89 {
  90   mLock = PR_NewLock();
  91   if (!mLock)
  92     return NS_ERROR_OUT_OF_MEMORY;
  93
  94   if (!mThreadsByPRThread.Init())
  95     return NS_ERROR_OUT_OF_MEMORY;
  96
  97   if (PR_NewThreadPrivateIndex(&mCurThreadIndex, ReleaseObject) == PR_FAILURE)
  98     return NS_ERROR_FAILURE;
  99
 100   // Setup "main" thread
 101   mMainThread = new nsThread();
 102   if (!mMainThread)
 103     return NS_ERROR_OUT_OF_MEMORY;
 104
 105   nsresult rv = mMainThread->InitCurrentThread();
 106   if (NS_FAILED(rv)) {
 107     mMainThread = nsnull;
 108     return rv;
 109   }
 110
 111   // We need to keep a pointer to the current thread, so we can satisfy
 112   // GetIsMainThread calls that occur post-Shutdown.
 113   mMainThread->GetPRThread(&mMainPRThread);
 114
 115 #ifdef XP_WIN
 116   TlsSetValue(gTLSIsMainThreadIndex, (void*) 1);
 117 #elif defined(NS_TLS)
 118   gTLSIsMainThread = true;
 119 #endif
 120
 121   mInitialized = PR_TRUE;
 122   return NS_OK;
 123 }
 124
 125 void
 126 nsThreadManager::Shutdown()
 127 {
 128   NS_ASSERTION(NS_IsMainThread(), "shutdown not called from main thread");
 129
 130   // Prevent further access to the thread manager (no more new threads!)
 131   //
 132   // XXX What happens if shutdown happens before NewThread completes?
 133   //     Fortunately, NewThread is only called on the main thread for now.
 134   //
 135   mInitialized = PR_FALSE;
 136
 137   // Empty the main thread event queue before we begin shutting down threads.
 138   NS_ProcessPendingEvents(mMainThread);
 139
 140   // We gather the threads from the hashtable into a list, so that we avoid
 141   // holding the hashtable lock while calling nsIThread::Shutdown.
 142   nsThreadArray threads;
 143   {
 144     nsAutoLock lock(mLock);
 145     mThreadsByPRThread.Enumerate(AppendAndRemoveThread, &threads);
 146   }
 147
 148   // It's tempting to walk the list of threads here and tell them each to stop
 149   // accepting new events, but that could lead to badness if one of those
 150   // threads is stuck waiting for a response from another thread.  To do it
 151   // right, we'd need some way to interrupt the threads.
 152   //
 153   // Instead, we process events on the current thread while waiting for threads
 154   // to shutdown.  This means that we have to preserve a mostly functioning
 155   // world until such time as the threads exit.
 156
 157   // Shutdown all threads that require it (join with threads that we created).
 158   for (PRUint32 i = 0; i < threads.Length(); ++i) {
 159     nsThread *thread = threads[i];
 160     if (thread->ShutdownRequired())
 161       thread->Shutdown();
 162   }
 163
 164   // In case there are any more events somehow...
 165   NS_ProcessPendingEvents(mMainThread);
 166
 167   // There are no more background threads at this point.
 168
 169   // Clear the table of threads.
 170   {
 171     nsAutoLock lock(mLock);
 172     mThreadsByPRThread.Clear();
 173   }
 174
 175   // Normally thread shutdown clears the observer for the thread, but since the
 176   // main thread is special we do it manually here after we're sure all events
 177   // have been processed.
 178   mMainThread->SetObserver(nsnull);
 179
 180   // Release main thread object.
 181   mMainThread = nsnull;
 182
 183   // Remove the TLS entry for the main thread.
 184   PR_SetThreadPrivate(mCurThreadIndex, nsnull);
 185
 186   // We don't need this lock anymore.
 187   PR_DestroyLock(mLock);
 188   mLock = nsnull;
 189 }
 190
 191 void
 192 nsThreadManager::RegisterCurrentThread(nsThread *thread)
 193 {
 194   NS_ASSERTION(thread->GetPRThread() == PR_GetCurrentThread(), "bad thread");
 195
 196   nsAutoLock lock(mLock);
 197
 198   mThreadsByPRThread.Put(thread->GetPRThread(), thread);  // XXX check OOM?
 199
 200   NS_ADDREF(thread);  // for TLS entry
 201   PR_SetThreadPrivate(mCurThreadIndex, thread);
 202 }
 203
 204 void
 205 nsThreadManager::UnregisterCurrentThread(nsThread *thread)
 206 {
 207   NS_ASSERTION(thread->GetPRThread() == PR_GetCurrentThread(), "bad thread");
 208
 209   nsAutoLock lock(mLock);
 210
 211   mThreadsByPRThread.Remove(thread->GetPRThread());
 212
 213   PR_SetThreadPrivate(mCurThreadIndex, nsnull);
 214   // Ref-count balanced via ReleaseObject
 215 }
 216
 217 nsThread *
 218 nsThreadManager::GetCurrentThread()
 219 {
 220   // read thread local storage
 221   void *data = PR_GetThreadPrivate(mCurThreadIndex);
 222   if (data)
 223     return static_cast<nsThread *>(data);
 224
 225   if (!mInitialized) {
 226     return nsnull;
 227   }
 228
 229   // OK, that's fine.  We'll dynamically create one :-)
 230   nsRefPtr<nsThread> thread = new nsThread();
 231   if (!thread || NS_FAILED(thread->InitCurrentThread()))
 232     return nsnull;
 233
 234   return thread.get();  // reference held in TLS
 235 }
 236
 237 NS_IMETHODIMP
 238 nsThreadManager::NewThread(PRUint32 creationFlags, nsIThread **result)
 239 {
 240   // No new threads during Shutdown
 241   NS_ENSURE_TRUE(mInitialized, NS_ERROR_NOT_INITIALIZED);
 242
 243   nsThread *thr = new nsThread();
 244   if (!thr)
 245     return NS_ERROR_OUT_OF_MEMORY;
 246   NS_ADDREF(thr);
 247
 248   nsresult rv = thr->Init();
 249   if (NS_FAILED(rv)) {
 250     NS_RELEASE(thr);
 251     return rv;
 252   }
 253
 254   // At this point, we expect that the thread has been registered in mThread;
 255   // however, it is possible that it could have also been replaced by now, so
 256   // we cannot really assert that it was added.
 257
 258   *result = thr;
 259   return NS_OK;
 260 }
 261
 262 NS_IMETHODIMP
 263 nsThreadManager::GetThreadFromPRThread(PRThread *thread, nsIThread **result)
 264 {
 265   // Keep this functioning during Shutdown
 266   NS_ENSURE_TRUE(mMainThread, NS_ERROR_NOT_INITIALIZED);
 267   NS_ENSURE_ARG_POINTER(thread);
 268
 269   nsRefPtr<nsThread> temp;
 270   {
 271     nsAutoLock lock(mLock);
 272     mThreadsByPRThread.Get(thread, getter_AddRefs(temp));
 273   }
 274
 275   NS_IF_ADDREF(*result = temp);
 276   return NS_OK;
 277 }
 278
 279 NS_IMETHODIMP
 280 nsThreadManager::GetMainThread(nsIThread **result)
 281 {
 282   // Keep this functioning during Shutdown
 283   NS_ENSURE_TRUE(mMainThread, NS_ERROR_NOT_INITIALIZED);
 284   NS_ADDREF(*result = mMainThread);
 285   return NS_OK;
 286 }
 287
 288 NS_IMETHODIMP
 289 nsThreadManager::GetCurrentThread(nsIThread **result)
 290 {
 291   // Keep this functioning during Shutdown
 292   NS_ENSURE_TRUE(mMainThread, NS_ERROR_NOT_INITIALIZED);
 293   *result = GetCurrentThread();
 294   if (!*result)
 295     return NS_ERROR_OUT_OF_MEMORY;
 296   NS_ADDREF(*result);
 297   return NS_OK;
 298 }
 299
 300 NS_IMETHODIMP
 301 nsThreadManager::GetIsMainThread(PRBool *result)
 302 {
 303   // This method may be called post-Shutdown
 304
 305   *result = (PR_GetCurrentThread() == mMainPRThread);
 306   return NS_OK;
 307 }