xpcom/threads/nsThreadPool.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
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  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 "nsIProxyObjectManager.h"
  40 #include "nsIClassInfoImpl.h"
  41 #include "nsThreadPool.h"
  42 #include "nsThreadManager.h"
  43 #include "nsThread.h"
  44 #include "nsMemory.h"
  45 #include "nsAutoPtr.h"
  46 #include "nsAutoLock.h"
  47 #include "prinrval.h"
  48 #include "prlog.h"
  49
  50 #ifdef PR_LOGGING
  51 static PRLogModuleInfo *sLog = PR_NewLogModule("nsThreadPool");
  52 #endif
  53 #define LOG(args) PR_LOG(sLog, PR_LOG_DEBUG, args)
  54
  55 // DESIGN:
  56 //  o  Allocate anonymous threads.
  57 //  o  Use nsThreadPool::Run as the main routine for each thread.
  58 //  o  Each thread waits on the event queue's monitor, checking for
  59 //     pending events and rescheduling itself as an idle thread.
  60
  61 #define DEFAULT_THREAD_LIMIT 4
  62 #define DEFAULT_IDLE_THREAD_LIMIT 1
  63 #define DEFAULT_IDLE_THREAD_TIMEOUT PR_SecondsToInterval(60)
  64
  65 NS_IMPL_THREADSAFE_ADDREF(nsThreadPool)
  66 NS_IMPL_THREADSAFE_RELEASE(nsThreadPool)
  67 NS_IMPL_QUERY_INTERFACE3_CI(nsThreadPool, nsIThreadPool, nsIEventTarget,
  68                             nsIRunnable)
  69 NS_IMPL_CI_INTERFACE_GETTER2(nsThreadPool, nsIThreadPool, nsIEventTarget)
  70
  71 nsThreadPool::nsThreadPool()
  72   : mThreadLimit(DEFAULT_THREAD_LIMIT)
  73   , mIdleThreadLimit(DEFAULT_IDLE_THREAD_LIMIT)
  74   , mIdleThreadTimeout(DEFAULT_IDLE_THREAD_TIMEOUT)
  75   , mIdleCount(0)
  76   , mShutdown(PR_FALSE)
  77 {
  78 }
  79
  80 nsThreadPool::~nsThreadPool()
  81 {
  82   Shutdown();
  83 }
  84
  85 nsresult
  86 nsThreadPool::PutEvent(nsIRunnable *event)
  87 {
  88   // Avoid spawning a new thread while holding the event queue lock...
  89
  90   PRBool spawnThread = PR_FALSE;
  91   {
  92     nsAutoMonitor mon(mEvents.Monitor());
  93
  94     LOG(("THRD-P(%p) put [%d %d %d]\n", this, mIdleCount, mThreads.Count(),
  95          mThreadLimit));
  96     NS_ASSERTION(mIdleCount <= (PRUint32) mThreads.Count(), "oops");
  97
  98     // Make sure we have a thread to service this event.
  99     if (mIdleCount == 0 && mThreads.Count() < (PRInt32) mThreadLimit)
 100       spawnThread = PR_TRUE;
 101
 102     mEvents.PutEvent(event);
 103   }
 104
 105   LOG(("THRD-P(%p) put [spawn=%d]\n", this, spawnThread));
 106   if (!spawnThread)
 107     return NS_OK;
 108
 109   nsCOMPtr<nsIThread> thread;
 110   nsThreadManager::get()->NewThread(0, getter_AddRefs(thread));
 111   NS_ENSURE_STATE(thread);
 112
 113   PRBool killThread = PR_FALSE;
 114   {
 115     nsAutoMonitor mon(mEvents.Monitor());
 116     if (mThreads.Count() < (PRInt32) mThreadLimit) {
 117       mThreads.AppendObject(thread);
 118     } else {
 119       killThread = PR_TRUE;  // okay, we don't need this thread anymore
 120     }
 121   }
 122   LOG(("THRD-P(%p) put [%p kill=%d]\n", this, thread.get(), killThread));
 123   if (killThread) {
 124     thread->Shutdown();
 125   } else {
 126     thread->Dispatch(this, NS_DISPATCH_NORMAL);
 127   }
 128
 129   return NS_OK;
 130 }
 131
 132 void
 133 nsThreadPool::ShutdownThread(nsIThread *thread)
 134 {
 135   LOG(("THRD-P(%p) shutdown async [%p]\n", this, thread));
 136
 137   // This method is responsible for calling Shutdown on |thread|.  This must be
 138   // done from some other thread, so we use the main thread of the application.
 139
 140   NS_ASSERTION(!NS_IsMainThread(), "wrong thread");
 141
 142   nsCOMPtr<nsIThread> doomed;
 143   NS_GetProxyForObject(NS_PROXY_TO_MAIN_THREAD, NS_GET_IID(nsIThread), thread,
 144                        NS_PROXY_ASYNC, getter_AddRefs(doomed));
 145   if (doomed) {
 146     doomed->Shutdown();
 147   } else {
 148     NS_WARNING("failed to construct proxy to main thread");
 149   }
 150 }
 151
 152 NS_IMETHODIMP
 153 nsThreadPool::Run()
 154 {
 155   LOG(("THRD-P(%p) enter\n", this));
 156
 157   nsCOMPtr<nsIThread> current;
 158   nsThreadManager::get()->GetCurrentThread(getter_AddRefs(current));
 159
 160   PRBool shutdownThreadOnExit = PR_FALSE;
 161   PRBool exitThread = PR_FALSE;
 162   PRBool wasIdle = PR_FALSE;
 163   PRIntervalTime idleSince;
 164
 165   nsCOMPtr<nsIThreadPoolListener> listener;
 166   {
 167     nsAutoMonitor mon(mEvents.Monitor());
 168     listener = mListener;
 169   }
 170
 171   if (listener) {
 172     listener->OnThreadCreated();
 173   }
 174
 175   do {
 176     nsCOMPtr<nsIRunnable> event;
 177     {
 178       nsAutoMonitor mon(mEvents.Monitor());
 179       if (!mEvents.GetPendingEvent(getter_AddRefs(event))) {
 180         PRIntervalTime now     = PR_IntervalNow();
 181         PRIntervalTime timeout = PR_MillisecondsToInterval(mIdleThreadTimeout);
 182
 183         // If we are shutting down, then don't keep any idle threads
 184         if (mShutdown) {
 185           exitThread = PR_TRUE;
 186         } else {
 187           if (wasIdle) {
 188             // if too many idle threads or idle for too long, then bail.
 189             if (mIdleCount > mIdleThreadLimit || (now - idleSince) >= timeout)
 190               exitThread = PR_TRUE;
 191           } else {
 192             // if would be too many idle threads...
 193             if (mIdleCount == mIdleThreadLimit) {
 194               exitThread = PR_TRUE;
 195             } else {
 196               ++mIdleCount;
 197               idleSince = now;
 198               wasIdle = PR_TRUE;
 199             }
 200           }
 201         }
 202
 203         if (exitThread) {
 204           if (wasIdle)
 205             --mIdleCount;
 206           shutdownThreadOnExit = mThreads.RemoveObject(current);
 207         } else {
 208           PRIntervalTime delta = timeout - (now - idleSince);
 209           LOG(("THRD-P(%p) waiting [%d]\n", this, delta));
 210           mon.Wait(delta);
 211         }
 212       } else if (wasIdle) {
 213         wasIdle = PR_FALSE;
 214         --mIdleCount;
 215       }
 216     }
 217     if (event) {
 218       LOG(("THRD-P(%p) running [%p]\n", this, event.get()));
 219       event->Run();
 220     }
 221   } while (!exitThread);
 222
 223   if (listener) {
 224     listener->OnThreadShuttingDown();
 225   }
 226
 227   if (shutdownThreadOnExit) {
 228     ShutdownThread(current);
 229   }
 230
 231   LOG(("THRD-P(%p) leave\n", this));
 232   return NS_OK;
 233 }
 234
 235 NS_IMETHODIMP
 236 nsThreadPool::Dispatch(nsIRunnable *event, PRUint32 flags)
 237 {
 238   LOG(("THRD-P(%p) dispatch [%p %x]\n", this, event, flags));
 239
 240   NS_ENSURE_STATE(!mShutdown);
 241
 242   if (flags & DISPATCH_SYNC) {
 243     nsCOMPtr<nsIThread> thread;
 244     nsThreadManager::get()->GetCurrentThread(getter_AddRefs(thread));
 245     NS_ENSURE_STATE(thread);
 246
 247     nsRefPtr<nsThreadSyncDispatch> wrapper =
 248         new nsThreadSyncDispatch(thread, event);
 249     PutEvent(wrapper);
 250
 251     while (wrapper->IsPending())
 252       NS_ProcessNextEvent(thread);
 253   } else {
 254     NS_ASSERTION(flags == NS_DISPATCH_NORMAL, "unexpected dispatch flags");
 255     PutEvent(event);
 256   }
 257   return NS_OK;
 258 }
 259
 260 NS_IMETHODIMP
 261 nsThreadPool::IsOnCurrentThread(PRBool *result)
 262 {
 263   // No one should be calling this method.  If this assertion gets hit, then we
 264   // need to think carefully about what this method should be returning.
 265   NS_NOTREACHED("implement me");
 266
 267   *result = PR_FALSE;
 268   return NS_OK;
 269 }
 270
 271 NS_IMETHODIMP
 272 nsThreadPool::Shutdown()
 273 {
 274   nsCOMArray<nsIThread> threads;
 275   nsCOMPtr<nsIThreadPoolListener> listener;
 276   {
 277     nsAutoMonitor mon(mEvents.Monitor());
 278     mShutdown = PR_TRUE;
 279     mon.NotifyAll();
 280
 281     threads.AppendObjects(mThreads);
 282     mThreads.Clear();
 283
 284     // Swap in a null listener so that we release the listener at the end of
 285     // this method. The listener will be kept alive as long as the other threads
 286     // that were created when it was set.
 287     mListener.swap(listener);
 288   }
 289
 290   // It's important that we shutdown the threads while outside the event queue
 291   // monitor.  Otherwise, we could end up dead-locking.
 292
 293   for (PRInt32 i = 0; i < threads.Count(); ++i)
 294     threads[i]->Shutdown();
 295
 296   return NS_OK;
 297 }
 298
 299 NS_IMETHODIMP
 300 nsThreadPool::GetThreadLimit(PRUint32 *value)
 301 {
 302   *value = mThreadLimit;
 303   return NS_OK;
 304 }
 305
 306 NS_IMETHODIMP
 307 nsThreadPool::SetThreadLimit(PRUint32 value)
 308 {
 309   nsAutoMonitor mon(mEvents.Monitor());
 310   mThreadLimit = value;
 311   if (mIdleThreadLimit > mThreadLimit)
 312     mIdleThreadLimit = mThreadLimit;
 313   mon.NotifyAll();  // wake up threads so they observe this change
 314   return NS_OK;
 315 }
 316
 317 NS_IMETHODIMP
 318 nsThreadPool::GetIdleThreadLimit(PRUint32 *value)
 319 {
 320   *value = mIdleThreadLimit;
 321   return NS_OK;
 322 }
 323
 324 NS_IMETHODIMP
 325 nsThreadPool::SetIdleThreadLimit(PRUint32 value)
 326 {
 327   nsAutoMonitor mon(mEvents.Monitor());
 328   mIdleThreadLimit = value;
 329   if (mIdleThreadLimit > mThreadLimit)
 330     mIdleThreadLimit = mThreadLimit;
 331   mon.NotifyAll();  // wake up threads so they observe this change
 332   return NS_OK;
 333 }
 334
 335 NS_IMETHODIMP
 336 nsThreadPool::GetIdleThreadTimeout(PRUint32 *value)
 337 {
 338   *value = mIdleThreadTimeout;
 339   return NS_OK;
 340 }
 341
 342 NS_IMETHODIMP
 343 nsThreadPool::SetIdleThreadTimeout(PRUint32 value)
 344 {
 345   nsAutoMonitor mon(mEvents.Monitor());
 346   mIdleThreadTimeout = value;
 347   mon.NotifyAll();  // wake up threads so they observe this change
 348   return NS_OK;
 349 }
 350
 351 NS_IMETHODIMP
 352 nsThreadPool::GetListener(nsIThreadPoolListener** aListener)
 353 {
 354   nsAutoMonitor mon(mEvents.Monitor());
 355   NS_IF_ADDREF(*aListener = mListener);
 356   return NS_OK;
 357 }
 358
 359 NS_IMETHODIMP
 360 nsThreadPool::SetListener(nsIThreadPoolListener* aListener)
 361 {
 362   nsCOMPtr<nsIThreadPoolListener> swappedListener(aListener);
 363   {
 364     nsAutoMonitor mon(mEvents.Monitor());
 365     mListener.swap(swappedListener);
 366   }
 367   return NS_OK;
 368 }