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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  32  * decision by deleting the provisions above and replace them with the notice
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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_CLASSINFO(nsThreadPool, NULL, nsIClassInfo::THREADSAFE,
  68                   NS_THREADPOOL_CID)
  69 NS_IMPL_QUERY_INTERFACE3_CI(nsThreadPool, nsIThreadPool, nsIEventTarget,
  70                             nsIRunnable)
  71 NS_IMPL_CI_INTERFACE_GETTER2(nsThreadPool, nsIThreadPool, nsIEventTarget)
  72
  73 nsThreadPool::nsThreadPool()
  74   : mThreadLimit(DEFAULT_THREAD_LIMIT)
  75   , mIdleThreadLimit(DEFAULT_IDLE_THREAD_LIMIT)
  76   , mIdleThreadTimeout(DEFAULT_IDLE_THREAD_TIMEOUT)
  77   , mIdleCount(0)
  78   , mShutdown(PR_FALSE)
  79 {
  80 }
  81
  82 nsThreadPool::~nsThreadPool()
  83 {
  84   Shutdown();
  85 }
  86
  87 nsresult
  88 nsThreadPool::PutEvent(nsIRunnable *event)
  89 {
  90   // Avoid spawning a new thread while holding the event queue lock...
  91
  92   PRBool spawnThread = PR_FALSE;
  93   {
  94     nsAutoMonitor mon(mEvents.Monitor());
  95
  96     LOG(("THRD-P(%p) put [%d %d %d]\n", this, mIdleCount, mThreads.Count(),
  97          mThreadLimit));
  98     NS_ASSERTION(mIdleCount <= (PRUint32) mThreads.Count(), "oops");
  99
 100     // Make sure we have a thread to service this event.
 101     if (mIdleCount == 0 && mThreads.Count() < (PRInt32) mThreadLimit)
 102       spawnThread = PR_TRUE;
 103
 104     mEvents.PutEvent(event);
 105   }
 106
 107   LOG(("THRD-P(%p) put [spawn=%d]\n", this, spawnThread));
 108   if (!spawnThread)
 109     return NS_OK;
 110
 111   nsCOMPtr<nsIThread> thread;
 112   nsThreadManager::get()->NewThread(0, getter_AddRefs(thread));
 113   NS_ENSURE_STATE(thread);
 114
 115   PRBool killThread = PR_FALSE;
 116   {
 117     nsAutoMonitor mon(mEvents.Monitor());
 118     if (mThreads.Count() < (PRInt32) mThreadLimit) {
 119       mThreads.AppendObject(thread);
 120     } else {
 121       killThread = PR_TRUE;  // okay, we don't need this thread anymore
 122     }
 123   }
 124   LOG(("THRD-P(%p) put [%p kill=%d]\n", this, thread.get(), killThread));
 125   if (killThread) {
 126     thread->Shutdown();
 127   } else {
 128     thread->Dispatch(this, NS_DISPATCH_NORMAL);
 129   }
 130
 131   return NS_OK;
 132 }
 133
 134 void
 135 nsThreadPool::ShutdownThread(nsIThread *thread)
 136 {
 137   LOG(("THRD-P(%p) shutdown async [%p]\n", this, thread));
 138
 139   // This method is responsible for calling Shutdown on |thread|.  This must be
 140   // done from some other thread, so we use the main thread of the application.
 141
 142   NS_ASSERTION(!NS_IsMainThread(), "wrong thread");
 143
 144   nsCOMPtr<nsIThread> doomed;
 145   NS_GetProxyForObject(NS_PROXY_TO_MAIN_THREAD, NS_GET_IID(nsIThread), thread,
 146                        NS_PROXY_ASYNC, getter_AddRefs(doomed));
 147   if (doomed) {
 148     doomed->Shutdown();
 149   } else {
 150     NS_WARNING("failed to construct proxy to main thread");
 151   }
 152 }
 153
 154 NS_IMETHODIMP
 155 nsThreadPool::Run()
 156 {
 157   LOG(("THRD-P(%p) enter\n", this));
 158
 159   nsCOMPtr<nsIThread> current;
 160   nsThreadManager::get()->GetCurrentThread(getter_AddRefs(current));
 161
 162   PRBool shutdownThreadOnExit = PR_FALSE;
 163   PRBool exitThread = PR_FALSE;
 164   PRBool wasIdle = PR_FALSE;
 165   PRIntervalTime idleSince;
 166
 167   nsCOMPtr<nsIThreadPoolListener> listener;
 168   {
 169     nsAutoMonitor mon(mEvents.Monitor());
 170     listener = mListener;
 171   }
 172
 173   if (listener) {
 174     listener->OnThreadCreated();
 175   }
 176
 177   do {
 178     nsCOMPtr<nsIRunnable> event;
 179     {
 180       nsAutoMonitor mon(mEvents.Monitor());
 181       if (!mEvents.GetPendingEvent(getter_AddRefs(event))) {
 182         PRIntervalTime now     = PR_IntervalNow();
 183         PRIntervalTime timeout = PR_MillisecondsToInterval(mIdleThreadTimeout);
 184
 185         // If we are shutting down, then don't keep any idle threads
 186         if (mShutdown) {
 187           exitThread = PR_TRUE;
 188         } else {
 189           if (wasIdle) {
 190             // if too many idle threads or idle for too long, then bail.
 191             if (mIdleCount > mIdleThreadLimit || (now - idleSince) >= timeout)
 192               exitThread = PR_TRUE;
 193           } else {
 194             // if would be too many idle threads...
 195             if (mIdleCount == mIdleThreadLimit) {
 196               exitThread = PR_TRUE;
 197             } else {
 198               ++mIdleCount;
 199               idleSince = now;
 200               wasIdle = PR_TRUE;
 201             }
 202           }
 203         }
 204
 205         if (exitThread) {
 206           if (wasIdle)
 207             --mIdleCount;
 208           shutdownThreadOnExit = mThreads.RemoveObject(current);
 209         } else {
 210           PRIntervalTime delta = timeout - (now - idleSince);
 211           LOG(("THRD-P(%p) waiting [%d]\n", this, delta));
 212           mon.Wait(delta);
 213         }
 214       } else if (wasIdle) {
 215         wasIdle = PR_FALSE;
 216         --mIdleCount;
 217       }
 218     }
 219     if (event) {
 220       LOG(("THRD-P(%p) running [%p]\n", this, event.get()));
 221       event->Run();
 222     }
 223   } while (!exitThread);
 224
 225   if (listener) {
 226     listener->OnThreadShuttingDown();
 227   }
 228
 229   if (shutdownThreadOnExit) {
 230     ShutdownThread(current);
 231   }
 232
 233   LOG(("THRD-P(%p) leave\n", this));
 234   return NS_OK;
 235 }
 236
 237 NS_IMETHODIMP
 238 nsThreadPool::Dispatch(nsIRunnable *event, PRUint32 flags)
 239 {
 240   LOG(("THRD-P(%p) dispatch [%p %x]\n", this, event, flags));
 241
 242   NS_ENSURE_STATE(!mShutdown);
 243
 244   if (flags & DISPATCH_SYNC) {
 245     nsCOMPtr<nsIThread> thread;
 246     nsThreadManager::get()->GetCurrentThread(getter_AddRefs(thread));
 247     NS_ENSURE_STATE(thread);
 248
 249     nsRefPtr<nsThreadSyncDispatch> wrapper =
 250         new nsThreadSyncDispatch(thread, event);
 251     PutEvent(wrapper);
 252
 253     while (wrapper->IsPending())
 254       NS_ProcessNextEvent(thread);
 255   } else {
 256     NS_ASSERTION(flags == NS_DISPATCH_NORMAL, "unexpected dispatch flags");
 257     PutEvent(event);
 258   }
 259   return NS_OK;
 260 }
 261
 262 NS_IMETHODIMP
 263 nsThreadPool::IsOnCurrentThread(PRBool *result)
 264 {
 265   // No one should be calling this method.  If this assertion gets hit, then we
 266   // need to think carefully about what this method should be returning.
 267   NS_NOTREACHED("implement me");
 268
 269   *result = PR_FALSE;
 270   return NS_OK;
 271 }
 272
 273 NS_IMETHODIMP
 274 nsThreadPool::Shutdown()
 275 {
 276   nsCOMArray<nsIThread> threads;
 277   nsCOMPtr<nsIThreadPoolListener> listener;
 278   {
 279     nsAutoMonitor mon(mEvents.Monitor());
 280     mShutdown = PR_TRUE;
 281     mon.NotifyAll();
 282
 283     threads.AppendObjects(mThreads);
 284     mThreads.Clear();
 285
 286     // Swap in a null listener so that we release the listener at the end of
 287     // this method. The listener will be kept alive as long as the other threads
 288     // that were created when it was set.
 289     mListener.swap(listener);
 290   }
 291
 292   // It's important that we shutdown the threads while outside the event queue
 293   // monitor.  Otherwise, we could end up dead-locking.
 294
 295   for (PRInt32 i = 0; i < threads.Count(); ++i)
 296     threads[i]->Shutdown();
 297
 298   return NS_OK;
 299 }
 300
 301 NS_IMETHODIMP
 302 nsThreadPool::GetThreadLimit(PRUint32 *value)
 303 {
 304   *value = mThreadLimit;
 305   return NS_OK;
 306 }
 307
 308 NS_IMETHODIMP
 309 nsThreadPool::SetThreadLimit(PRUint32 value)
 310 {
 311   nsAutoMonitor mon(mEvents.Monitor());
 312   mThreadLimit = value;
 313   if (mIdleThreadLimit > mThreadLimit)
 314     mIdleThreadLimit = mThreadLimit;
 315   mon.NotifyAll();  // wake up threads so they observe this change
 316   return NS_OK;
 317 }
 318
 319 NS_IMETHODIMP
 320 nsThreadPool::GetIdleThreadLimit(PRUint32 *value)
 321 {
 322   *value = mIdleThreadLimit;
 323   return NS_OK;
 324 }
 325
 326 NS_IMETHODIMP
 327 nsThreadPool::SetIdleThreadLimit(PRUint32 value)
 328 {
 329   nsAutoMonitor mon(mEvents.Monitor());
 330   mIdleThreadLimit = value;
 331   if (mIdleThreadLimit > mThreadLimit)
 332     mIdleThreadLimit = mThreadLimit;
 333   mon.NotifyAll();  // wake up threads so they observe this change
 334   return NS_OK;
 335 }
 336
 337 NS_IMETHODIMP
 338 nsThreadPool::GetIdleThreadTimeout(PRUint32 *value)
 339 {
 340   *value = mIdleThreadTimeout;
 341   return NS_OK;
 342 }
 343
 344 NS_IMETHODIMP
 345 nsThreadPool::SetIdleThreadTimeout(PRUint32 value)
 346 {
 347   nsAutoMonitor mon(mEvents.Monitor());
 348   mIdleThreadTimeout = value;
 349   mon.NotifyAll();  // wake up threads so they observe this change
 350   return NS_OK;
 351 }
 352
 353 NS_IMETHODIMP
 354 nsThreadPool::GetListener(nsIThreadPoolListener** aListener)
 355 {
 356   nsAutoMonitor mon(mEvents.Monitor());
 357   NS_IF_ADDREF(*aListener = mListener);
 358   return NS_OK;
 359 }
 360
 361 NS_IMETHODIMP
 362 nsThreadPool::SetListener(nsIThreadPoolListener* aListener)
 363 {
 364   nsCOMPtr<nsIThreadPoolListener> swappedListener(aListener);
 365   {
 366     nsAutoMonitor mon(mEvents.Monitor());
 367     mListener.swap(swappedListener);
 368   }
 369   return NS_OK;
 370 }