gecko-dev/xpcom/threads/nsEventQueueService.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Communicator client code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Rick Potts <rpotts@netscape.com>
 *   Ramiro Estrugo <ramiro@netscape.com>
 *   Warren Harris <warren@netscape.com>
 *   Leaf Nunes <leaf@mozilla.org>
 *   David Matiskella <davidm@netscape.com>
 *   David Hyatt <hyatt@netscape.com>
 *   Seth Spitzer <sspitzer@netscape.com>
 *   Suresh Duddi <dp@netscape.com>
 *   Bruce Mitchener <bruce@cybersight.com>
 *   Scott Collins <scc@netscape.com>
 *   Daniel Matejka <danm@netscape.com>
 *   Doug Turner <dougt@netscape.com>
 *   Stuart Parmenter <pavlov@netscape.com>
 *   Mike Kaply <mkaply@us.ibm.com>
 *   Dan Mosedale <dmose@mozilla.org>
 *   Benjamin Smedberg <benjamin@smedbergs.us>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsEventQueueService.h"
#include "prmon.h"
#include "nsIComponentManager.h"
#include "nsIThread.h"
#include "nsPIEventQueueChain.h"
#include "nsAutoLock.h"

#include "prlog.h"

#if defined(PR_LOGGING) || defined(DEBUG_danm)
extern PRLogModuleInfo* gEventQueueLog;
extern PRUint32 gEventQueueLogCount;
#endif

static NS_DEFINE_CID(kEventQueueCID, NS_EVENTQUEUE_CID);

nsEventQueueServiceImpl::nsEventQueueServiceImpl()
  : mEventQMonitor(PR_NewMonitor())
  , mIsShuttingDown(PR_FALSE)
{
#if defined(PR_LOGGING) && defined(DEBUG_danm)
  if (!gEventQueueLog)
    gEventQueueLog = PR_NewLogModule("nseventqueue");
#endif
}

PR_STATIC_CALLBACK(PLDHashOperator)
hash_enum_remove_queues(const void *aThread_ptr,
                        nsCOMPtr<nsPIEventQueueChain>& aEldestQueue,
                        void* closure)
{
  aEldestQueue->StopAcceptingEvents();
  return PL_DHASH_REMOVE;
}

void
nsEventQueueServiceImpl::Shutdown()
{
  NS_ASSERTION(mEventQTable.Count() <= 1,
               "Event queues for secondary threads exist during shutdown.");

  nsAutoMonitor mon(mEventQMonitor);
  mIsShuttingDown = PR_TRUE;

  // Call StopAcceptingEvents on any queues that are left: this should be only
  // the main-thread event queue at this point, since xpcom-shutdown-threads has
  // already been notified.
  mEventQTable.Enumerate(hash_enum_remove_queues, nsnull);
}

nsEventQueueServiceImpl::~nsEventQueueServiceImpl()
{
  if (mEventQMonitor)
    PR_DestroyMonitor(mEventQMonitor);
}

nsresult
nsEventQueueServiceImpl::Init()
{
  NS_ENSURE_TRUE(mEventQMonitor, NS_ERROR_OUT_OF_MEMORY);

  // This will only be called once on the main thread, so it's safe to
  // not enter the monitor here.
  if (!mEventQTable.Init()) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // ensure that a main thread event queue exists!
  nsresult rv;
  nsCOMPtr<nsIThread> mainThread;
  rv = nsIThread::GetMainThread(getter_AddRefs(mainThread));
  if (NS_SUCCEEDED(rv)) {
    PRThread *thr;
    rv = mainThread->GetPRThread(&thr);
    if (NS_SUCCEEDED(rv))
      rv = CreateEventQueue(thr, PR_TRUE);
  }
  return rv;
}

/* nsISupports interface implementation... */
// QI to our CID so that NS_ShutdownXPCOM can call our internal methods
NS_IMPL_THREADSAFE_ISUPPORTS2(nsEventQueueServiceImpl,
                              nsIEventQueueService,
                              nsEventQueueServiceImpl)

/* nsIEventQueueService interface implementation... */

NS_IMETHODIMP
nsEventQueueServiceImpl::CreateThreadEventQueue()
{
  return CreateEventQueue(PR_GetCurrentThread(), PR_TRUE);
}

NS_IMETHODIMP
nsEventQueueServiceImpl::CreateMonitoredThreadEventQueue()
{
  return CreateEventQueue(PR_GetCurrentThread(), PR_FALSE);
}

NS_IMETHODIMP
nsEventQueueServiceImpl::CreateFromIThread(nsIThread *aThread, PRBool aNative,
                                           nsIEventQueue **aResult)
{
  nsresult rv;
  PRThread *prThread;

  rv = aThread->GetPRThread(&prThread);
  if (NS_SUCCEEDED(rv)) {
    rv = CreateEventQueue(prThread, aNative); // addrefs
    if (NS_SUCCEEDED(rv))
      rv = GetThreadEventQueue(prThread, aResult); // addrefs
  }
  return rv;
}

// private method
NS_IMETHODIMP
nsEventQueueServiceImpl::MakeNewQueue(PRThread* thread,
                                      PRBool aNative,
                                      nsPIEventQueueChain **aQueue)
{
  nsresult rv;
  nsCOMPtr<nsPIEventQueueChain> queue(do_CreateInstance(kEventQueueCID, &rv));

  if (NS_SUCCEEDED(rv)) {
    rv = queue->InitFromPRThread(thread, aNative);
    if (NS_FAILED(rv))
      queue = nsnull;
  }
  *aQueue = queue;
  NS_IF_ADDREF(*aQueue);
  return rv;
}

// private method
NS_IMETHODIMP
nsEventQueueServiceImpl::CreateEventQueue(PRThread *aThread, PRBool aNative)
{
  nsresult rv;

  nsAutoMonitor mon(mEventQMonitor);

  if (mIsShuttingDown)
    return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;

  /* create only one event queue chain per thread... */
  if (mEventQTable.GetWeak(aThread))
    return NS_OK;

  nsCOMPtr<nsPIEventQueueChain> queue;

  // we don't have one in the table, create new queue
  rv = MakeNewQueue(aThread, aNative, getter_AddRefs(queue));
  if (NS_SUCCEEDED(rv))
    mEventQTable.Put(aThread, queue); // add to the table (initial addref)

  return rv;
}


NS_IMETHODIMP
nsEventQueueServiceImpl::DestroyThreadEventQueue(void)
{
  /* Enter the lock that protects the EventQ hashtable... */
  nsAutoMonitor mon(mEventQMonitor);

  PRThread* currentThread = PR_GetCurrentThread();
  nsPIEventQueueChain* queue = mEventQTable.GetWeak(currentThread);
  if (queue) {
    queue->StopAcceptingEvents(); // tell the queue to stop accepting events
    queue = nsnull; // Queue may die on the next line
    mEventQTable.Remove(currentThread); // remove nsIEventQueue from hash table (releases)
  }

  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueServiceImpl::CreateFromPLEventQueue(PLEventQueue* aPLEventQueue,
                                                nsIEventQueue** aResult)
{
  // Create our thread queue using the component manager
  nsresult rv;
  nsCOMPtr<nsIEventQueue> queue = do_CreateInstance(kEventQueueCID, &rv);
  if (NS_FAILED(rv)) return rv;

  rv = queue->InitFromPLQueue(aPLEventQueue);
  if (NS_FAILED(rv)) return rv;

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


// Return the active event queue on our chain
/* inline */
nsresult nsEventQueueServiceImpl::GetYoungestEventQueue(nsIEventQueue *queue, nsIEventQueue **aResult)
{
  nsCOMPtr<nsIEventQueue> answer;

  if (queue) {
    nsCOMPtr<nsPIEventQueueChain> ourChain(do_QueryInterface(queue));
    if (ourChain)
      ourChain->GetYoungestActive(getter_AddRefs(answer));
    else
      answer = queue;
  }

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


// create new event queue, append it to the current thread's chain of event queues.
// return it, addrefed.
NS_IMETHODIMP
nsEventQueueServiceImpl::PushThreadEventQueue(nsIEventQueue **aNewQueue)
{
  nsresult rv;

  PRThread* currentThread = PR_GetCurrentThread();
  PRBool native = PR_TRUE; // native by default as per old comment

  NS_ASSERTION(aNewQueue, "PushThreadEventQueue called with null param");

  /* Enter the lock that protects the EventQ hashtable... */
  nsAutoMonitor mon(mEventQMonitor);

  nsPIEventQueueChain* queue = mEventQTable.GetWeak(currentThread);

  NS_ASSERTION(queue, "pushed event queue on top of nothing");

  if (queue) { // find out what kind of queue our relatives are
    nsCOMPtr<nsIEventQueue> youngQueue;
    GetYoungestEventQueue(queue, getter_AddRefs(youngQueue));
    if (youngQueue) {
      youngQueue->IsQueueNative(&native);
    }
  }

  nsPIEventQueueChain* newQueue = nsnull;
  rv = MakeNewQueue(currentThread, native, &newQueue);  // AddRefs on success
  NS_ENSURE_SUCCESS(rv, rv);

  if (!queue) {
    // shouldn't happen. as a fallback, we guess you wanted a native queue
    mEventQTable.Put(currentThread, newQueue);
  }

  // append the new queue to the event queue chain
  queue->AppendQueue(newQueue);

  *aNewQueue = newQueue;

#if defined(PR_LOGGING) && defined(DEBUG_danm)
  PLEventQueue *equeue;
  (*aNewQueue)->GetPLEventQueue(&equeue);
  PR_LOG(gEventQueueLog, PR_LOG_DEBUG,
         ("EventQueue: Service push queue [queue=%lx]",(long)equeue));
  ++gEventQueueLogCount;
#endif

  return NS_OK;
}

// disable and release the given queue (though the last one won't be released)
NS_IMETHODIMP
nsEventQueueServiceImpl::PopThreadEventQueue(nsIEventQueue *aQueue)
{
  PRThread* currentThread = PR_GetCurrentThread();

  nsCOMPtr<nsPIEventQueueChain> eldestQueue;

  {
    nsAutoMonitor mon(mEventQMonitor);
    mEventQTable.Get(currentThread, getter_AddRefs(eldestQueue));

    // If we are popping the eldest queue, remove its mEventQTable entry.
    if (aQueue == eldestQueue)
      mEventQTable.Remove(currentThread);
  }

  // Exit the monitor before processing pending events to avoid deadlock.
  // Our reference from the eldestQueue nsCOMPtr will keep that object alive.
  // Since it is thread-private, no one else can race with us here.
  if (!eldestQueue)
    return NS_ERROR_FAILURE;

#if defined(PR_LOGGING) && defined(DEBUG_danm)
  PLEventQueue *equeue;
  aQueue->GetPLEventQueue(&equeue);
  PR_LOG(gEventQueueLog, PR_LOG_DEBUG,
         ("EventQueue: Service pop queue [queue=%lx]",(long)equeue));
  ++gEventQueueLogCount;
#endif
  aQueue->StopAcceptingEvents();
  aQueue->ProcessPendingEvents(); // make sure we don't orphan any events

  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueServiceImpl::GetThreadEventQueue(PRThread* aThread, nsIEventQueue** aResult)
{
  /* Parameter validation... */
  if (NULL == aResult) return NS_ERROR_NULL_POINTER;

  PRThread* keyThread = aThread;

  if (keyThread == NS_CURRENT_THREAD)
  {
     keyThread = PR_GetCurrentThread();
  }
  else if (keyThread == NS_UI_THREAD)
  {
    nsCOMPtr<nsIThread>  mainIThread;

    // Get the primordial thread
    nsresult rv = nsIThread::GetMainThread(getter_AddRefs(mainIThread));
    if (NS_FAILED(rv)) return rv;

    rv = mainIThread->GetPRThread(&keyThread);
    if (NS_FAILED(rv)) return rv;
  }

  nsCOMPtr<nsPIEventQueueChain> queue;

  {
    nsAutoMonitor mon(mEventQMonitor);
    mEventQTable.Get(keyThread, getter_AddRefs(queue));
  }

  if (queue) {
    GetYoungestEventQueue(queue, aResult); // get the youngest active queue
  } else {
    *aResult = nsnull;
  }
  // XXX: Need error code for requesting an event queue when none exists...
  if (!*aResult) {
    return NS_ERROR_NOT_AVAILABLE;
  }
  return NS_OK;
}


NS_IMETHODIMP
nsEventQueueServiceImpl::ResolveEventQueue(nsIEventQueue* queueOrConstant, nsIEventQueue* *resultQueue)
{
  if (queueOrConstant == NS_CURRENT_EVENTQ) {
    return GetThreadEventQueue(NS_CURRENT_THREAD, resultQueue);
  }
  else if (queueOrConstant == NS_UI_THREAD_EVENTQ) {
    return GetThreadEventQueue(NS_UI_THREAD, resultQueue);
  }

  *resultQueue = queueOrConstant;
  NS_ADDREF(*resultQueue);
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueServiceImpl::GetSpecialEventQueue(PRInt32 aQueue,
                                              nsIEventQueue* *_retval)
{
  nsresult rv;

  // barf if someone gave us a zero pointer
  //
  if (!_retval) {
    return NS_ERROR_NULL_POINTER;
  }

  // try and get the requested event queue, returning NS_ERROR_FAILURE if there
  // is a problem.  GetThreadEventQueue() does the AddRef() for us.
  //
  switch (aQueue) {
  case CURRENT_THREAD_EVENT_QUEUE:
    rv = GetThreadEventQueue(NS_CURRENT_THREAD, _retval);
    if (NS_FAILED(rv)) {
      return NS_ERROR_FAILURE;
    }
    break;

  case UI_THREAD_EVENT_QUEUE:
    rv = GetThreadEventQueue(NS_UI_THREAD, _retval);
    if (NS_FAILED(rv)) {
      return NS_ERROR_FAILURE;
    }
    break;

    // somebody handed us a bogus constant
    //
  default:
    return NS_ERROR_ILLEGAL_VALUE;
  }

  return NS_OK;
}