DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (d38398e5144e)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsThreadManager.h"
#include "nsThread.h"
#include "nsThreadUtils.h"
#include "nsIClassInfoImpl.h"
#include "nsTArray.h"
#include "nsAutoPtr.h"
#include "mozilla/ThreadLocal.h"
#ifdef MOZ_CANARY
#include <fcntl.h>
#include <unistd.h>
#endif

#include "MainThreadIdlePeriod.h"

using namespace mozilla;

static MOZ_THREAD_LOCAL(bool) sTLSIsMainThread;

bool
NS_IsMainThread()
{
  return sTLSIsMainThread.get();
}

void
NS_SetMainThread()
{
  if (!sTLSIsMainThread.init()) {
    MOZ_CRASH();
  }
  sTLSIsMainThread.set(true);
  MOZ_ASSERT(NS_IsMainThread());
}

typedef nsTArray<NotNull<RefPtr<nsThread>>> nsThreadArray;

//-----------------------------------------------------------------------------

static void
ReleaseObject(void* aData)
{
  static_cast<nsISupports*>(aData)->Release();
}

// statically allocated instance
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::AddRef()
{
  return 2;
}
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::Release()
{
  return 1;
}
NS_IMPL_CLASSINFO(nsThreadManager, nullptr,
                  nsIClassInfo::THREADSAFE | nsIClassInfo::SINGLETON,
                  NS_THREADMANAGER_CID)
NS_IMPL_QUERY_INTERFACE_CI(nsThreadManager, nsIThreadManager)
NS_IMPL_CI_INTERFACE_GETTER(nsThreadManager, nsIThreadManager)

//-----------------------------------------------------------------------------

nsresult
nsThreadManager::Init()
{
  // Child processes need to initialize the thread manager before they
  // initialize XPCOM in order to set up the crash reporter. This leads to
  // situations where we get initialized twice.
  if (mInitialized) {
    return NS_OK;
  }

  if (PR_NewThreadPrivateIndex(&mCurThreadIndex, ReleaseObject) == PR_FAILURE) {
    return NS_ERROR_FAILURE;
  }


#ifdef MOZ_CANARY
  const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NONBLOCK;
  const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
  char* env_var_flag = getenv("MOZ_KILL_CANARIES");
  sCanaryOutputFD =
    env_var_flag ? (env_var_flag[0] ? open(env_var_flag, flags, mode) :
                                      STDERR_FILENO) :
                   0;
#endif

  // Setup "main" thread
  mMainThread = new nsThread(nsThread::MAIN_THREAD, 0);

  nsresult rv = mMainThread->InitCurrentThread();
  if (NS_FAILED(rv)) {
    mMainThread = nullptr;
    return rv;
  }

  {
    nsCOMPtr<nsIIdlePeriod> idlePeriod = new MainThreadIdlePeriod();
    mMainThread->RegisterIdlePeriod(idlePeriod.forget());
  }

  // We need to keep a pointer to the current thread, so we can satisfy
  // GetIsMainThread calls that occur post-Shutdown.
  mMainThread->GetPRThread(&mMainPRThread);

  mInitialized = true;
  return NS_OK;
}

void
nsThreadManager::Shutdown()
{
  MOZ_ASSERT(NS_IsMainThread(), "shutdown not called from main thread");

  // Prevent further access to the thread manager (no more new threads!)
  //
  // What happens if shutdown happens before NewThread completes?
  // We Shutdown() the new thread, and return error if we've started Shutdown
  // between when NewThread started, and when the thread finished initializing
  // and registering with ThreadManager.
  //
  mInitialized = false;

  // Empty the main thread event queue before we begin shutting down threads.
  NS_ProcessPendingEvents(mMainThread);

  // We gather the threads from the hashtable into a list, so that we avoid
  // holding the hashtable lock while calling nsIThread::Shutdown.
  nsThreadArray threads;
  {
    OffTheBooksMutexAutoLock lock(mLock);
    for (auto iter = mThreadsByPRThread.Iter(); !iter.Done(); iter.Next()) {
      RefPtr<nsThread>& thread = iter.Data();
      threads.AppendElement(WrapNotNull(thread));
      iter.Remove();
    }
  }

  // It's tempting to walk the list of threads here and tell them each to stop
  // accepting new events, but that could lead to badness if one of those
  // threads is stuck waiting for a response from another thread.  To do it
  // right, we'd need some way to interrupt the threads.
  //
  // Instead, we process events on the current thread while waiting for threads
  // to shutdown.  This means that we have to preserve a mostly functioning
  // world until such time as the threads exit.

  // Shutdown all threads that require it (join with threads that we created).
  for (uint32_t i = 0; i < threads.Length(); ++i) {
    NotNull<nsThread*> thread = threads[i];
    if (thread->ShutdownRequired()) {
      thread->Shutdown();
    }
  }

  // NB: It's possible that there are events in the queue that want to *start*
  // an asynchronous shutdown. But we have already shutdown the threads above,
  // so there's no need to worry about them. We only have to wait for all
  // in-flight asynchronous thread shutdowns to complete.
  mMainThread->WaitForAllAsynchronousShutdowns();

  // In case there are any more events somehow...
  NS_ProcessPendingEvents(mMainThread);

  // There are no more background threads at this point.

  // Clear the table of threads.
  {
    OffTheBooksMutexAutoLock lock(mLock);
    mThreadsByPRThread.Clear();
  }

  // Normally thread shutdown clears the observer for the thread, but since the
  // main thread is special we do it manually here after we're sure all events
  // have been processed.
  mMainThread->SetObserver(nullptr);
  mMainThread->ClearObservers();

  // Release main thread object.
  mMainThread = nullptr;

  // Remove the TLS entry for the main thread.
  PR_SetThreadPrivate(mCurThreadIndex, nullptr);
}

void
nsThreadManager::RegisterCurrentThread(nsThread& aThread)
{
  MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");

  OffTheBooksMutexAutoLock lock(mLock);

  ++mCurrentNumberOfThreads;
  if (mCurrentNumberOfThreads > mHighestNumberOfThreads) {
    mHighestNumberOfThreads = mCurrentNumberOfThreads;
  }

  mThreadsByPRThread.Put(aThread.GetPRThread(), &aThread);  // XXX check OOM?

  aThread.AddRef();  // for TLS entry
  PR_SetThreadPrivate(mCurThreadIndex, &aThread);
}

void
nsThreadManager::UnregisterCurrentThread(nsThread& aThread)
{
  MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");

  OffTheBooksMutexAutoLock lock(mLock);

  --mCurrentNumberOfThreads;
  mThreadsByPRThread.Remove(aThread.GetPRThread());

  PR_SetThreadPrivate(mCurThreadIndex, nullptr);
  // Ref-count balanced via ReleaseObject
}

nsThread*
nsThreadManager::GetCurrentThread()
{
  // read thread local storage
  void* data = PR_GetThreadPrivate(mCurThreadIndex);
  if (data) {
    return static_cast<nsThread*>(data);
  }

  if (!mInitialized) {
    return nullptr;
  }

  // OK, that's fine.  We'll dynamically create one :-)
  RefPtr<nsThread> thread = new nsThread(nsThread::NOT_MAIN_THREAD, 0);
  if (!thread || NS_FAILED(thread->InitCurrentThread())) {
    return nullptr;
  }

  return thread.get();  // reference held in TLS
}

NS_IMETHODIMP
nsThreadManager::NewThread(uint32_t aCreationFlags,
                           uint32_t aStackSize,
                           nsIThread** aResult)
{
  return NewNamedThread(NS_LITERAL_CSTRING(""), aStackSize, aResult);
}

NS_IMETHODIMP
nsThreadManager::NewNamedThread(const nsACString& aName,
                                uint32_t aStackSize,
                                nsIThread** aResult)
{
  // Note: can be called from arbitrary threads
  
  // No new threads during Shutdown
  if (NS_WARN_IF(!mInitialized)) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  RefPtr<nsThread> thr = new nsThread(nsThread::NOT_MAIN_THREAD, aStackSize);
  nsresult rv = thr->Init(aName);  // Note: blocks until the new thread has been set up
  if (NS_FAILED(rv)) {
    return rv;
  }

  // At this point, we expect that the thread has been registered in mThreadByPRThread;
  // however, it is possible that it could have also been replaced by now, so
  // we cannot really assert that it was added.  Instead, kill it if we entered
  // Shutdown() during/before Init()

  if (NS_WARN_IF(!mInitialized)) {
    if (thr->ShutdownRequired()) {
      thr->Shutdown(); // ok if it happens multiple times
    }
    return NS_ERROR_NOT_INITIALIZED;
  }

  thr.forget(aResult);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetThreadFromPRThread(PRThread* aThread, nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  if (NS_WARN_IF(!aThread)) {
    return NS_ERROR_INVALID_ARG;
  }

  RefPtr<nsThread> temp;
  {
    OffTheBooksMutexAutoLock lock(mLock);
    mThreadsByPRThread.Get(aThread, getter_AddRefs(temp));
  }

  NS_IF_ADDREF(*aResult = temp);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetMainThread(nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  NS_ADDREF(*aResult = mMainThread);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetCurrentThread(nsIThread** aResult)
{
  // Keep this functioning during Shutdown
  if (NS_WARN_IF(!mMainThread)) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  *aResult = GetCurrentThread();
  if (!*aResult) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  NS_ADDREF(*aResult);
  return NS_OK;
}

NS_IMETHODIMP
nsThreadManager::GetIsMainThread(bool* aResult)
{
  // This method may be called post-Shutdown

  *aResult = (PR_GetCurrentThread() == mMainPRThread);
  return NS_OK;
}

uint32_t
nsThreadManager::GetHighestNumberOfThreads()
{
  OffTheBooksMutexAutoLock lock(mLock);
  return mHighestNumberOfThreads;
}