summaryrefslogtreecommitdiffstats
path: root/ipc/glue/MessagePump.cpp
blob: 45b4c7f14a5713b650ada7c7740fda972ff8fe7c (plain)
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
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "MessagePump.h"

#include "nsIRunnable.h"
#include "nsIThread.h"
#include "nsITimer.h"
#include "nsICancelableRunnable.h"

#include "base/basictypes.h"
#include "base/logging.h"
#include "base/scoped_nsautorelease_pool.h"
#include "mozilla/Assertions.h"
#include "mozilla/DebugOnly.h"
#include "nsComponentManagerUtils.h"
#include "nsDebug.h"
#include "nsServiceManagerUtils.h"
#include "nsString.h"
#include "nsThreadUtils.h"
#include "nsTimerImpl.h"
#include "nsXULAppAPI.h"
#include "prthread.h"

using base::TimeTicks;
using namespace mozilla::ipc;

NS_DEFINE_NAMED_CID(NS_TIMER_CID);

#ifdef DEBUG
static MessagePump::Delegate* gFirstDelegate;
#endif

namespace mozilla {
namespace ipc {

class DoWorkRunnable final : public CancelableRunnable,
                             public nsITimerCallback
{
public:
  explicit DoWorkRunnable(MessagePump* aPump)
  : mPump(aPump)
  {
    MOZ_ASSERT(aPump);
  }

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIRUNNABLE
  NS_DECL_NSITIMERCALLBACK
  nsresult Cancel() override;

private:
  ~DoWorkRunnable()
  { }

  MessagePump* mPump;
  // DoWorkRunnable is designed as a stateless singleton.  Do not add stateful
  // members here!
};

} /* namespace ipc */
} /* namespace mozilla */

MessagePump::MessagePump(nsIThread* aThread)
: mThread(aThread)
{
  mDoWorkEvent = new DoWorkRunnable(this);
}

MessagePump::~MessagePump()
{
}

void
MessagePump::Run(MessagePump::Delegate* aDelegate)
{
  MOZ_ASSERT(keep_running_);
  MOZ_RELEASE_ASSERT(NS_IsMainThread(),
                     "Use mozilla::ipc::MessagePumpForNonMainThreads instead!");
  MOZ_RELEASE_ASSERT(!mThread);

  nsIThread* thisThread = NS_GetCurrentThread();
  MOZ_ASSERT(thisThread);

  mDelayedWorkTimer = do_CreateInstance(kNS_TIMER_CID);
  MOZ_ASSERT(mDelayedWorkTimer);

  base::ScopedNSAutoreleasePool autoReleasePool;

  for (;;) {
    autoReleasePool.Recycle();

    bool did_work = NS_ProcessNextEvent(thisThread, false) ? true : false;
    if (!keep_running_)
      break;

    // NB: it is crucial *not* to directly call |aDelegate->DoWork()|
    // here.  To ensure that MessageLoop tasks and XPCOM events have
    // equal priority, we sensitively rely on processing exactly one
    // Task per DoWorkRunnable XPCOM event.

    did_work |= aDelegate->DoDelayedWork(&delayed_work_time_);

if (did_work && delayed_work_time_.is_null())
      mDelayedWorkTimer->Cancel();

    if (!keep_running_)
      break;

    if (did_work)
      continue;

    did_work = aDelegate->DoIdleWork();
    if (!keep_running_)
      break;

    if (did_work)
      continue;

    // This will either sleep or process an event.
    NS_ProcessNextEvent(thisThread, true);
  }

    mDelayedWorkTimer->Cancel();

  keep_running_ = true;
}

void
MessagePump::ScheduleWork()
{
  // Make sure the event loop wakes up.
  if (mThread) {
    mThread->Dispatch(mDoWorkEvent, NS_DISPATCH_NORMAL);
  } else {
    // Some things (like xpcshell) don't use the app shell and so Run hasn't
    // been called. We still need to wake up the main thread.
    NS_DispatchToMainThread(mDoWorkEvent);
  }
  event_.Signal();
}

void
MessagePump::ScheduleWorkForNestedLoop()
{
  // This method is called when our MessageLoop has just allowed
  // nested tasks.  In our setup, whenever that happens we know that
  // DoWork() will be called "soon", so there's no need to pay the
  // cost of what will be a no-op nsThread::Dispatch(mDoWorkEvent).
}

void
MessagePump::ScheduleDelayedWork(const base::TimeTicks& aDelayedTime)
{
  // To avoid racing on mDelayedWorkTimer, we need to be on the same thread as
  // ::Run().
  MOZ_RELEASE_ASSERT(NS_GetCurrentThread() == mThread ||
                     (!mThread && NS_IsMainThread()));

  if (!mDelayedWorkTimer) {
    mDelayedWorkTimer = do_CreateInstance(kNS_TIMER_CID);
    if (!mDelayedWorkTimer) {
        // Called before XPCOM has started up? We can't do this correctly.
        NS_WARNING("Delayed task might not run!");
        delayed_work_time_ = aDelayedTime;
        return;
    }
  }

  if (!delayed_work_time_.is_null()) {
    mDelayedWorkTimer->Cancel();
  }

  delayed_work_time_ = aDelayedTime;

  // TimeDelta's constructor initializes to 0
  base::TimeDelta delay;
  if (aDelayedTime > base::TimeTicks::Now())
    delay = aDelayedTime - base::TimeTicks::Now();

  uint32_t delayMS = uint32_t(delay.InMilliseconds());
  mDelayedWorkTimer->InitWithCallback(mDoWorkEvent, delayMS,
                                      nsITimer::TYPE_ONE_SHOT);
}

nsIEventTarget*
MessagePump::GetXPCOMThread()
{
  if (mThread) {
    return mThread;
  }

  // Main thread
  nsCOMPtr<nsIThread> mainThread = do_GetMainThread();
  return mainThread;
}

void
MessagePump::DoDelayedWork(base::MessagePump::Delegate* aDelegate)
{
  aDelegate->DoDelayedWork(&delayed_work_time_);
  if (!delayed_work_time_.is_null()) {
    ScheduleDelayedWork(delayed_work_time_);
  }
}

NS_IMPL_ISUPPORTS_INHERITED(DoWorkRunnable, CancelableRunnable,
                            nsITimerCallback)

NS_IMETHODIMP
DoWorkRunnable::Run()
{
  MessageLoop* loop = MessageLoop::current();
  MOZ_ASSERT(loop);

  bool nestableTasksAllowed = loop->NestableTasksAllowed();

  // MessageLoop::RunTask() disallows nesting, but our Frankenventloop will
  // always dispatch DoWork() below from what looks to MessageLoop like a nested
  // context.  So we unconditionally allow nesting here.
  loop->SetNestableTasksAllowed(true);
  loop->DoWork();
  loop->SetNestableTasksAllowed(nestableTasksAllowed);

  return NS_OK;
}

NS_IMETHODIMP
DoWorkRunnable::Notify(nsITimer* aTimer)
{
  MessageLoop* loop = MessageLoop::current();
  MOZ_ASSERT(loop);

  bool nestableTasksAllowed = loop->NestableTasksAllowed();
  loop->SetNestableTasksAllowed(true);
  mPump->DoDelayedWork(loop);
  loop->SetNestableTasksAllowed(nestableTasksAllowed);

  return NS_OK;
}

nsresult
DoWorkRunnable::Cancel()
{
  // Workers require cancelable runnables, but we can't really cancel cleanly
  // here.  If we don't process this runnable then we will leave something
  // unprocessed in the message_loop.  Therefore, eagerly complete our work
  // instead by immediately calling Run().  Run() should be called separately
  // after this.  Unfortunately we cannot use flags to verify this because
  // DoWorkRunnable is a stateless singleton that can be in the event queue
  // multiple times simultaneously.
  MOZ_ALWAYS_SUCCEEDS(Run());
  return NS_OK;
}

void
MessagePumpForChildProcess::Run(base::MessagePump::Delegate* aDelegate)
{
  if (mFirstRun) {
    MOZ_ASSERT(aDelegate && !gFirstDelegate);
#ifdef DEBUG
    gFirstDelegate = aDelegate;
#endif

    mFirstRun = false;
    if (NS_FAILED(XRE_RunAppShell())) {
        NS_WARNING("Failed to run app shell?!");
    }

    MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);
#ifdef DEBUG
    gFirstDelegate = nullptr;
#endif

    return;
  }

  MOZ_ASSERT(aDelegate && aDelegate == gFirstDelegate);

  // We can get to this point in startup with Tasks in our loop's
  // incoming_queue_ or pending_queue_, but without a matching
  // DoWorkRunnable().  In MessagePump::Run() above, we sensitively
  // depend on *not* directly calling delegate->DoWork(), because that
  // prioritizes Tasks above XPCOM events.  However, from this point
  // forward, any Task posted to our loop is guaranteed to have a
  // DoWorkRunnable enqueued for it.
  //
  // So we just flush the pending work here and move on.
  MessageLoop* loop = MessageLoop::current();
  bool nestableTasksAllowed = loop->NestableTasksAllowed();
  loop->SetNestableTasksAllowed(true);

  while (aDelegate->DoWork());

  loop->SetNestableTasksAllowed(nestableTasksAllowed);

  // Really run.
  mozilla::ipc::MessagePump::Run(aDelegate);
}

void
MessagePumpForNonMainThreads::Run(base::MessagePump::Delegate* aDelegate)
{
  MOZ_ASSERT(keep_running_);
  MOZ_RELEASE_ASSERT(!NS_IsMainThread(), "Use mozilla::ipc::MessagePump instead!");

  nsIThread* thread = NS_GetCurrentThread();
  MOZ_RELEASE_ASSERT(mThread == thread);

  mDelayedWorkTimer = do_CreateInstance(kNS_TIMER_CID);
  MOZ_ASSERT(mDelayedWorkTimer);

  if (NS_FAILED(mDelayedWorkTimer->SetTarget(thread))) {
    MOZ_CRASH("Failed to set timer target!");
  }

  // Chromium event notifications to be processed will be received by this
  // event loop as a DoWorkRunnables via ScheduleWork. Chromium events that
  // were received before our thread is valid, however, will not generate
  // runnable wrappers. We must process any of these before we enter this
  // loop, or we will forever have unprocessed chromium messages in our queue.
  //
  // Note we would like to request a flush of the chromium event queue
  // using a runnable on the xpcom side, but some thread implementations
  // (dom workers) get cranky if we call ScheduleWork here (ScheduleWork
  // calls dispatch on mThread) before the thread processes an event. As
  // such, clear the queue manually.
  while (aDelegate->DoWork()) {
  }

  base::ScopedNSAutoreleasePool autoReleasePool;
  for (;;) {
    autoReleasePool.Recycle();

    bool didWork = NS_ProcessNextEvent(thread, false) ? true : false;
    if (!keep_running_) {
      break;
    }

    didWork |= aDelegate->DoDelayedWork(&delayed_work_time_);

    if (didWork && delayed_work_time_.is_null()) {
      mDelayedWorkTimer->Cancel();
    }

    if (!keep_running_) {
      break;
    }

    if (didWork) {
      continue;
    }

    DebugOnly<bool> didIdleWork = aDelegate->DoIdleWork();
    MOZ_ASSERT(!didIdleWork);
    if (!keep_running_) {
      break;
    }

    if (didWork) {
      continue;
    }

    // This will either sleep or process an event.
    NS_ProcessNextEvent(thread, true);
  }

  mDelayedWorkTimer->Cancel();

  keep_running_ = true;
}

#if defined(XP_WIN)

NS_IMPL_QUERY_INTERFACE(MessagePumpForNonMainUIThreads, nsIThreadObserver)

#define CHECK_QUIT_STATE { if (state_->should_quit) { break; } }

void
MessagePumpForNonMainUIThreads::DoRunLoop()
{
  MOZ_RELEASE_ASSERT(!NS_IsMainThread(), "Use mozilla::ipc::MessagePump instead!");

  // If this is a chromium thread and no nsThread is associated
  // with it, this call will create a new nsThread.
  nsIThread* thread = NS_GetCurrentThread();
  MOZ_ASSERT(thread);

  // Set the main thread observer so we can wake up when
  // xpcom events need to get processed.
  nsCOMPtr<nsIThreadInternal> ti(do_QueryInterface(thread));
  MOZ_ASSERT(ti);
  ti->SetObserver(this);

  base::ScopedNSAutoreleasePool autoReleasePool;
  for (;;) {
    autoReleasePool.Recycle();

    bool didWork = NS_ProcessNextEvent(thread, false);

    didWork |= ProcessNextWindowsMessage();
    CHECK_QUIT_STATE

    didWork |= state_->delegate->DoWork();
    CHECK_QUIT_STATE

    didWork |= state_->delegate->DoDelayedWork(&delayed_work_time_);
    if (didWork && delayed_work_time_.is_null()) {
      KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));
    }
    CHECK_QUIT_STATE

    if (didWork) {
      continue;
    }

    DebugOnly<bool> didIdleWork = state_->delegate->DoIdleWork();
    MOZ_ASSERT(!didIdleWork);
    CHECK_QUIT_STATE

    SetInWait();
    bool hasWork = NS_HasPendingEvents(thread);
    if (didWork || hasWork) {
      ClearInWait();
      continue;
    }
    WaitForWork(); // Calls MsgWaitForMultipleObjectsEx(QS_ALLINPUT)
    ClearInWait();
  }

  ClearInWait();

  ti->SetObserver(nullptr);
}

NS_IMETHODIMP
MessagePumpForNonMainUIThreads::OnDispatchedEvent(nsIThreadInternal *thread)
{
  // If our thread is sleeping in DoRunLoop's call to WaitForWork() and an
  // event posts to the nsIThread event queue - break our thread out of
  // chromium's WaitForWork.
  if (GetInWait()) {
    ScheduleWork();
  }
  return NS_OK;
}

NS_IMETHODIMP
MessagePumpForNonMainUIThreads::OnProcessNextEvent(nsIThreadInternal *thread,
                                                   bool mayWait)
{
  return NS_OK;
}

NS_IMETHODIMP
MessagePumpForNonMainUIThreads::AfterProcessNextEvent(nsIThreadInternal *thread,
                                                      bool eventWasProcessed)
{
  return NS_OK;
}

#endif // XP_WIN