1/*
2 * Copyright (C) 2010 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "WorkQueue.h"
28
29#include <WebCore/NotImplemented.h>
30#include <wtf/Threading.h>
31
32inline WorkQueue::WorkItemWin::WorkItemWin(PassOwnPtr<WorkItem> item, WorkQueue* queue)
33    : m_item(item)
34    , m_queue(queue)
35{
36}
37
38PassRefPtr<WorkQueue::WorkItemWin> WorkQueue::WorkItemWin::create(PassOwnPtr<WorkItem> item, WorkQueue* queue)
39{
40    return adoptRef(new WorkItemWin(item, queue));
41}
42
43WorkQueue::WorkItemWin::~WorkItemWin()
44{
45}
46
47inline WorkQueue::HandleWorkItem::HandleWorkItem(HANDLE handle, PassOwnPtr<WorkItem> item, WorkQueue* queue)
48    : WorkItemWin(item, queue)
49    , m_handle(handle)
50    , m_waitHandle(0)
51{
52    ASSERT_ARG(handle, handle);
53}
54
55PassRefPtr<WorkQueue::HandleWorkItem> WorkQueue::HandleWorkItem::createByAdoptingHandle(HANDLE handle, PassOwnPtr<WorkItem> item, WorkQueue* queue)
56{
57    return adoptRef(new HandleWorkItem(handle, item, queue));
58}
59
60WorkQueue::HandleWorkItem::~HandleWorkItem()
61{
62    ::CloseHandle(m_handle);
63}
64
65void WorkQueue::handleCallback(void* context, BOOLEAN timerOrWaitFired)
66{
67    ASSERT_ARG(context, context);
68    ASSERT_ARG(timerOrWaitFired, !timerOrWaitFired);
69
70    WorkItemWin* item = static_cast<WorkItemWin*>(context);
71    WorkQueue* queue = item->queue();
72
73    {
74        MutexLocker lock(queue->m_workItemQueueLock);
75        queue->m_workItemQueue.append(item);
76
77        // If no other thread is performing work, we can do it on this thread.
78        if (!queue->tryRegisterAsWorkThread()) {
79            // Some other thread is performing work. Since we hold the queue lock, we can be sure
80            // that the work thread is not exiting due to an empty queue and will process the work
81            // item we just added to it. If we weren't holding the lock we'd have to signal
82            // m_performWorkEvent to make sure the work item got picked up.
83            return;
84        }
85    }
86
87    queue->performWorkOnRegisteredWorkThread();
88}
89
90void WorkQueue::registerHandle(HANDLE handle, PassOwnPtr<WorkItem> item)
91{
92    RefPtr<HandleWorkItem> handleItem = HandleWorkItem::createByAdoptingHandle(handle, item, this);
93
94    {
95        MutexLocker lock(m_handlesLock);
96        ASSERT_ARG(handle, !m_handles.contains(handle));
97        m_handles.set(handle, handleItem);
98    }
99
100    HANDLE waitHandle;
101    if (!::RegisterWaitForSingleObject(&waitHandle, handle, handleCallback, handleItem.get(), INFINITE, WT_EXECUTEDEFAULT)) {
102        DWORD error = ::GetLastError();
103        ASSERT_NOT_REACHED();
104    }
105    handleItem->setWaitHandle(waitHandle);
106}
107
108void WorkQueue::unregisterAndCloseHandle(HANDLE handle)
109{
110    RefPtr<HandleWorkItem> item;
111    {
112        MutexLocker locker(m_handlesLock);
113        ASSERT_ARG(handle, m_handles.contains(handle));
114        item = m_handles.take(handle);
115    }
116
117    unregisterWaitAndDestroyItemSoon(item.release());
118}
119
120DWORD WorkQueue::workThreadCallback(void* context)
121{
122    ASSERT_ARG(context, context);
123
124    WorkQueue* queue = static_cast<WorkQueue*>(context);
125
126    if (!queue->tryRegisterAsWorkThread())
127        return 0;
128
129    queue->performWorkOnRegisteredWorkThread();
130    return 0;
131}
132
133void WorkQueue::performWorkOnRegisteredWorkThread()
134{
135    ASSERT(m_isWorkThreadRegistered);
136
137    bool isValid = true;
138
139    m_workItemQueueLock.lock();
140
141    while (isValid && !m_workItemQueue.isEmpty()) {
142        Vector<RefPtr<WorkItemWin> > workItemQueue;
143        m_workItemQueue.swap(workItemQueue);
144
145        // Allow more work to be scheduled while we're not using the queue directly.
146        m_workItemQueueLock.unlock();
147        for (size_t i = 0; i < workItemQueue.size(); ++i) {
148            MutexLocker locker(m_isValidMutex);
149            isValid = m_isValid;
150            if (!isValid)
151                break;
152            workItemQueue[i]->item()->execute();
153        }
154        m_workItemQueueLock.lock();
155    }
156
157    // One invariant we maintain is that any work scheduled while a work thread is registered will
158    // be handled by that work thread. Unregister as the work thread while the queue lock is still
159    // held so that no work can be scheduled while we're still registered.
160    unregisterAsWorkThread();
161
162    m_workItemQueueLock.unlock();
163}
164
165void WorkQueue::platformInitialize(const char* name)
166{
167    m_isWorkThreadRegistered = 0;
168    m_timerQueue = ::CreateTimerQueue();
169    ASSERT_WITH_MESSAGE(m_timerQueue, "::CreateTimerQueue failed with error %lu", ::GetLastError());
170}
171
172bool WorkQueue::tryRegisterAsWorkThread()
173{
174    LONG result = ::InterlockedCompareExchange(&m_isWorkThreadRegistered, 1, 0);
175    ASSERT(!result || result == 1);
176    return !result;
177}
178
179void WorkQueue::unregisterAsWorkThread()
180{
181    LONG result = ::InterlockedCompareExchange(&m_isWorkThreadRegistered, 0, 1);
182    ASSERT_UNUSED(result, result == 1);
183}
184
185void WorkQueue::platformInvalidate()
186{
187#if !ASSERT_DISABLED
188    MutexLocker lock(m_handlesLock);
189    ASSERT(m_handles.isEmpty());
190#endif
191
192    // FIXME: We need to ensure that any timer-queue timers that fire after this point don't try to
193    // access this WorkQueue <http://webkit.org/b/44690>.
194    ::DeleteTimerQueueEx(m_timerQueue, 0);
195}
196
197void WorkQueue::scheduleWork(PassOwnPtr<WorkItem> item)
198{
199    MutexLocker locker(m_workItemQueueLock);
200
201    m_workItemQueue.append(WorkItemWin::create(item, this));
202
203    // Spawn a work thread to perform the work we just added. As an optimization, we avoid
204    // spawning the thread if a work thread is already registered. This prevents multiple work
205    // threads from being spawned in most cases. (Note that when a work thread has been spawned but
206    // hasn't registered itself yet, m_isWorkThreadRegistered will be false and we'll end up
207    // spawning a second work thread here. But work thread registration process will ensure that
208    // only one thread actually ends up performing work.)
209    if (!m_isWorkThreadRegistered)
210        ::QueueUserWorkItem(workThreadCallback, this, WT_EXECUTEDEFAULT);
211}
212
213struct TimerContext : public ThreadSafeRefCounted<TimerContext> {
214    static PassRefPtr<TimerContext> create() { return adoptRef(new TimerContext); }
215
216    WorkQueue* queue;
217    OwnPtr<WorkItem> item;
218    Mutex timerMutex;
219    HANDLE timer;
220
221private:
222    TimerContext() : queue(0), timer(0) { }
223};
224
225void WorkQueue::timerCallback(void* context, BOOLEAN timerOrWaitFired)
226{
227    ASSERT_ARG(context, context);
228    ASSERT_UNUSED(timerOrWaitFired, timerOrWaitFired);
229
230    // Balanced by leakRef in scheduleWorkAfterDelay.
231    RefPtr<TimerContext> timerContext = adoptRef(static_cast<TimerContext*>(context));
232
233    timerContext->queue->scheduleWork(timerContext->item.release());
234
235    MutexLocker lock(timerContext->timerMutex);
236    ASSERT(timerContext->timer);
237    ASSERT(timerContext->queue->m_timerQueue);
238    if (!::DeleteTimerQueueTimer(timerContext->queue->m_timerQueue, timerContext->timer, 0))
239        ASSERT_WITH_MESSAGE(false, "::DeleteTimerQueueTimer failed with error %lu", ::GetLastError());
240}
241
242void WorkQueue::scheduleWorkAfterDelay(PassOwnPtr<WorkItem> item, double delay)
243{
244    ASSERT(m_timerQueue);
245
246    RefPtr<TimerContext> context = TimerContext::create();
247    context->queue = this;
248    context->item = item;
249
250    {
251        // The timer callback could fire before ::CreateTimerQueueTimer even returns, so we protect
252        // context->timer with a mutex to ensure the timer callback doesn't access it before the
253        // timer handle has been stored in it.
254        MutexLocker lock(context->timerMutex);
255
256        // Since our timer callback is quick, we can execute in the timer thread itself and avoid
257        // an extra thread switch over to a worker thread.
258        if (!::CreateTimerQueueTimer(&context->timer, m_timerQueue, timerCallback, context.get(), delay * 1000, 0, WT_EXECUTEINTIMERTHREAD)) {
259            ASSERT_WITH_MESSAGE(false, "::CreateTimerQueueTimer failed with error %lu", ::GetLastError());
260            return;
261        }
262    }
263
264    // The timer callback will handle destroying context.
265    context.release().leakRef();
266}
267
268void WorkQueue::unregisterWaitAndDestroyItemSoon(PassRefPtr<HandleWorkItem> item)
269{
270    // We're going to make a blocking call to ::UnregisterWaitEx before closing the handle. (The
271    // blocking version of ::UnregisterWaitEx is much simpler than the non-blocking version.) If we
272    // do this on the current thread, we'll deadlock if we're currently in a callback function for
273    // the wait we're unregistering. So instead we do it asynchronously on some other worker thread.
274
275    ::QueueUserWorkItem(unregisterWaitAndDestroyItemCallback, item.leakRef(), WT_EXECUTEDEFAULT);
276}
277
278DWORD WINAPI WorkQueue::unregisterWaitAndDestroyItemCallback(void* context)
279{
280    ASSERT_ARG(context, context);
281    RefPtr<HandleWorkItem> item = adoptRef(static_cast<HandleWorkItem*>(context));
282
283    // Now that we know we're not in a callback function for the wait we're unregistering, we can
284    // make a blocking call to ::UnregisterWaitEx.
285    if (!::UnregisterWaitEx(item->waitHandle(), INVALID_HANDLE_VALUE)) {
286        DWORD error = ::GetLastError();
287        ASSERT_NOT_REACHED();
288    }
289
290    return 0;
291}
292