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- // Copyright (c) 2012 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "base/message_loop/message_pump_win.h"
- #include <algorithm>
- #include <cstdint>
- #include <type_traits>
- #include "base/auto_reset.h"
- #include "base/bind.h"
- #include "base/cxx17_backports.h"
- #include "base/debug/alias.h"
- #include "base/feature_list.h"
- #include "base/metrics/histogram_macros.h"
- #include "base/numerics/safe_conversions.h"
- #include "base/trace_event/base_tracing.h"
- #include "base/tracing_buildflags.h"
- #if BUILDFLAG(ENABLE_BASE_TRACING)
- #include "third_party/perfetto/protos/perfetto/trace/track_event/chrome_message_pump.pbzero.h"
- #endif // BUILDFLAG(ENABLE_BASE_TRACING)
- namespace base {
- namespace {
- enum MessageLoopProblems {
- MESSAGE_POST_ERROR,
- COMPLETION_POST_ERROR,
- SET_TIMER_ERROR,
- RECEIVED_WM_QUIT_ERROR,
- MESSAGE_LOOP_PROBLEM_MAX,
- };
- // Returns the number of milliseconds before |next_task_time|, clamped between
- // zero and the biggest DWORD value (or INFINITE if |next_task_time.is_max()|).
- // Optionally, a recent value of Now() may be passed in to avoid resampling it.
- DWORD GetSleepTimeoutMs(TimeTicks next_task_time,
- TimeTicks recent_now = TimeTicks()) {
- // Shouldn't need to sleep or install a timer when there's pending immediate
- // work.
- DCHECK(!next_task_time.is_null());
- if (next_task_time.is_max())
- return INFINITE;
- auto now = recent_now.is_null() ? TimeTicks::Now() : recent_now;
- auto timeout_ms = (next_task_time - now).InMillisecondsRoundedUp();
- // A saturated_cast with an unsigned destination automatically clamps negative
- // values at zero.
- static_assert(!std::is_signed<DWORD>::value, "DWORD is unexpectedly signed");
- return saturated_cast<DWORD>(timeout_ms);
- }
- } // namespace
- // Message sent to get an additional time slice for pumping (processing) another
- // task (a series of such messages creates a continuous task pump).
- static const int kMsgHaveWork = WM_USER + 1;
- //-----------------------------------------------------------------------------
- // MessagePumpWin public:
- MessagePumpWin::MessagePumpWin() = default;
- MessagePumpWin::~MessagePumpWin() = default;
- void MessagePumpWin::Run(Delegate* delegate) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- RunState run_state(delegate);
- if (run_state_)
- run_state.is_nested = true;
- AutoReset<RunState*> auto_reset_run_state(&run_state_, &run_state);
- DoRunLoop();
- }
- void MessagePumpWin::Quit() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- DCHECK(run_state_);
- run_state_->should_quit = true;
- }
- //-----------------------------------------------------------------------------
- // MessagePumpForUI public:
- MessagePumpForUI::MessagePumpForUI() {
- bool succeeded = message_window_.Create(
- BindRepeating(&MessagePumpForUI::MessageCallback, Unretained(this)));
- DCHECK(succeeded);
- }
- MessagePumpForUI::~MessagePumpForUI() = default;
- void MessagePumpForUI::ScheduleWork() {
- // This is the only MessagePumpForUI method which can be called outside of
- // |bound_thread_|.
- bool not_scheduled = false;
- if (!work_scheduled_.compare_exchange_strong(not_scheduled, true))
- return; // Someone else continued the pumping.
- // Make sure the MessagePump does some work for us.
- const BOOL ret = ::PostMessage(message_window_.hwnd(), kMsgHaveWork, 0, 0);
- if (ret)
- return; // There was room in the Window Message queue.
- // We have failed to insert a have-work message, so there is a chance that we
- // will starve tasks/timers while sitting in a nested run loop. Nested
- // loops only look at Windows Message queues, and don't look at *our* task
- // queues, etc., so we might not get a time slice in such. :-(
- // We could abort here, but the fear is that this failure mode is plausibly
- // common (queue is full, of about 2000 messages), so we'll do a near-graceful
- // recovery. Nested loops are pretty transient (we think), so this will
- // probably be recoverable.
- // Clarify that we didn't really insert.
- work_scheduled_ = false;
- UMA_HISTOGRAM_ENUMERATION("Chrome.MessageLoopProblem", MESSAGE_POST_ERROR,
- MESSAGE_LOOP_PROBLEM_MAX);
- TRACE_EVENT_INSTANT0("base", "Chrome.MessageLoopProblem.MESSAGE_POST_ERROR",
- TRACE_EVENT_SCOPE_THREAD);
- }
- void MessagePumpForUI::ScheduleDelayedWork(
- const Delegate::NextWorkInfo& next_work_info) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // Since this is always called from |bound_thread_|, there is almost always
- // nothing to do as the loop is already running. When the loop becomes idle,
- // it will typically WaitForWork() in DoRunLoop() with the timeout provided by
- // DoWork(). The only alternative to this is entering a native nested loop
- // (e.g. modal dialog) under a ScopedNestableTaskAllower, in which case
- // HandleWorkMessage() will be invoked when the system picks up kMsgHaveWork
- // and it will ScheduleNativeTimer() if it's out of immediate work. However,
- // in that alternate scenario : it's possible for a Windows native work item
- // (e.g. https://docs.microsoft.com/en-us/windows/desktop/winmsg/using-hooks)
- // to wake the native nested loop and PostDelayedTask() to the current thread
- // from it. This is the only case where we must install/adjust the native
- // timer from ScheduleDelayedWork() because if we don't, the native loop will
- // go back to sleep, unaware of the new |delayed_work_time|.
- // See MessageLoopTest.PostDelayedTaskFromSystemPump for an example.
- // TODO(gab): This could potentially be replaced by a ForegroundIdleProc hook
- // if Windows ends up being the only platform requiring ScheduleDelayedWork().
- if (in_native_loop_ && !work_scheduled_) {
- ScheduleNativeTimer(next_work_info);
- }
- }
- void MessagePumpForUI::AddObserver(Observer* observer) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- observers_.AddObserver(observer);
- }
- void MessagePumpForUI::RemoveObserver(Observer* observer) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- observers_.RemoveObserver(observer);
- }
- //-----------------------------------------------------------------------------
- // MessagePumpForUI private:
- bool MessagePumpForUI::MessageCallback(
- UINT message, WPARAM wparam, LPARAM lparam, LRESULT* result) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- switch (message) {
- case kMsgHaveWork:
- HandleWorkMessage();
- break;
- case WM_TIMER:
- if (wparam == reinterpret_cast<UINT_PTR>(this))
- HandleTimerMessage();
- break;
- }
- return false;
- }
- void MessagePumpForUI::DoRunLoop() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // IF this was just a simple PeekMessage() loop (servicing all possible work
- // queues), then Windows would try to achieve the following order according
- // to MSDN documentation about PeekMessage with no filter):
- // * Sent messages
- // * Posted messages
- // * Sent messages (again)
- // * WM_PAINT messages
- // * WM_TIMER messages
- //
- // Summary: none of the above classes is starved, and sent messages has twice
- // the chance of being processed (i.e., reduced service time).
- for (;;) {
- // If we do any work, we may create more messages etc., and more work may
- // possibly be waiting in another task group. When we (for example)
- // ProcessNextWindowsMessage(), there is a good chance there are still more
- // messages waiting. On the other hand, when any of these methods return
- // having done no work, then it is pretty unlikely that calling them again
- // quickly will find any work to do. Finally, if they all say they had no
- // work, then it is a good time to consider sleeping (waiting) for more
- // work.
- in_native_loop_ = false;
- bool more_work_is_plausible = ProcessNextWindowsMessage();
- in_native_loop_ = false;
- if (run_state_->should_quit)
- break;
- Delegate::NextWorkInfo next_work_info = run_state_->delegate->DoWork();
- in_native_loop_ = false;
- more_work_is_plausible |= next_work_info.is_immediate();
- if (run_state_->should_quit)
- break;
- if (installed_native_timer_) {
- // As described in ScheduleNativeTimer(), the native timer is only
- // installed and needed while in a nested native loop. If it is installed,
- // it means the above work entered such a loop. Having now resumed, the
- // native timer is no longer needed.
- KillNativeTimer();
- }
- if (more_work_is_plausible)
- continue;
- more_work_is_plausible = run_state_->delegate->DoIdleWork();
- // DoIdleWork() shouldn't end up in native nested loops and thus shouldn't
- // have any chance of reinstalling a native timer.
- DCHECK(!in_native_loop_);
- DCHECK(!installed_native_timer_);
- if (run_state_->should_quit)
- break;
- if (more_work_is_plausible)
- continue;
- WaitForWork(next_work_info);
- }
- }
- void MessagePumpForUI::WaitForWork(Delegate::NextWorkInfo next_work_info) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // Wait until a message is available, up to the time needed by the timer
- // manager to fire the next set of timers.
- DWORD wait_flags = MWMO_INPUTAVAILABLE;
- for (DWORD delay = GetSleepTimeoutMs(next_work_info.delayed_run_time,
- next_work_info.recent_now);
- delay != 0; delay = GetSleepTimeoutMs(next_work_info.delayed_run_time)) {
- run_state_->delegate->BeforeWait();
- // Tell the optimizer to retain these values to simplify analyzing hangs.
- base::debug::Alias(&delay);
- base::debug::Alias(&wait_flags);
- DWORD result = MsgWaitForMultipleObjectsEx(0, nullptr, delay, QS_ALLINPUT,
- wait_flags);
- if (WAIT_OBJECT_0 == result) {
- // A WM_* message is available.
- // If a parent child relationship exists between windows across threads
- // then their thread inputs are implicitly attached.
- // This causes the MsgWaitForMultipleObjectsEx API to return indicating
- // that messages are ready for processing (Specifically, mouse messages
- // intended for the child window may appear if the child window has
- // capture).
- // The subsequent PeekMessages call may fail to return any messages thus
- // causing us to enter a tight loop at times.
- // The code below is a workaround to give the child window
- // some time to process its input messages by looping back to
- // MsgWaitForMultipleObjectsEx above when there are no messages for the
- // current thread.
- // As in ProcessNextWindowsMessage().
- auto scoped_do_work_item = run_state_->delegate->BeginWorkItem();
- {
- TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("base"),
- "MessagePumpForUI::WaitForWork GetQueueStatus");
- if (HIWORD(::GetQueueStatus(QS_SENDMESSAGE)) & QS_SENDMESSAGE)
- return;
- }
- {
- MSG msg;
- TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("base"),
- "MessagePumpForUI::WaitForWork PeekMessage");
- if (::PeekMessage(&msg, nullptr, 0, 0, PM_NOREMOVE))
- return;
- }
- // We know there are no more messages for this thread because PeekMessage
- // has returned false. Reset |wait_flags| so that we wait for a *new*
- // message.
- wait_flags = 0;
- }
- DCHECK_NE(WAIT_FAILED, result) << GetLastError();
- }
- }
- void MessagePumpForUI::HandleWorkMessage() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // The kMsgHaveWork message was consumed by a native loop, we must assume
- // we're in one until DoRunLoop() gets control back.
- in_native_loop_ = true;
- // If we are being called outside of the context of Run, then don't try to do
- // any work. This could correspond to a MessageBox call or something of that
- // sort.
- if (!run_state_) {
- // Since we handled a kMsgHaveWork message, we must still update this flag.
- work_scheduled_ = false;
- return;
- }
- // Let whatever would have run had we not been putting messages in the queue
- // run now. This is an attempt to make our dummy message not starve other
- // messages that may be in the Windows message queue.
- ProcessPumpReplacementMessage();
- Delegate::NextWorkInfo next_work_info = run_state_->delegate->DoWork();
- if (next_work_info.is_immediate()) {
- ScheduleWork();
- } else {
- run_state_->delegate->BeforeWait();
- ScheduleNativeTimer(next_work_info);
- }
- }
- void MessagePumpForUI::HandleTimerMessage() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // ::KillTimer doesn't remove pending WM_TIMER messages from the queue,
- // explicitly ignore the last WM_TIMER message in that case to avoid handling
- // work from here when DoRunLoop() is active (which could result in scheduling
- // work from two places at once). Note: we're still fine in the event that a
- // second native nested loop is entered before such a dead WM_TIMER message is
- // discarded because ::SetTimer merely resets the timer if invoked twice with
- // the same id.
- if (!installed_native_timer_)
- return;
- // We only need to fire once per specific delay, another timer may be
- // scheduled below but we're done with this one.
- KillNativeTimer();
- // If we are being called outside of the context of Run, then don't do
- // anything. This could correspond to a MessageBox call or something of
- // that sort.
- if (!run_state_)
- return;
- Delegate::NextWorkInfo next_work_info = run_state_->delegate->DoWork();
- if (next_work_info.is_immediate()) {
- ScheduleWork();
- } else {
- run_state_->delegate->BeforeWait();
- ScheduleNativeTimer(next_work_info);
- }
- }
- void MessagePumpForUI::ScheduleNativeTimer(
- Delegate::NextWorkInfo next_work_info) {
- DCHECK(!next_work_info.is_immediate());
- DCHECK(in_native_loop_);
- // Do not redundantly set the same native timer again if it was already set.
- // This can happen when a nested native loop goes idle with pending delayed
- // tasks, then gets woken up by an immediate task, and goes back to idle with
- // the same pending delay. No need to kill the native timer if there is
- // already one but the |delayed_run_time| has changed as ::SetTimer reuses the
- // same id and will replace and reset the existing timer.
- if (installed_native_timer_ &&
- *installed_native_timer_ == next_work_info.delayed_run_time) {
- return;
- }
- if (next_work_info.delayed_run_time.is_max())
- return;
- // We do not use native Windows timers in general as they have a poor, 10ms,
- // granularity. Instead we rely on MsgWaitForMultipleObjectsEx's
- // high-resolution timeout to sleep without timers in WaitForWork(). However,
- // when entering a nested native ::GetMessage() loop (e.g. native modal
- // windows) under a ScopedNestableTaskAllower, we have to rely on a native
- // timer when HandleWorkMessage() runs out of immediate work. Since
- // ScopedNestableTaskAllower invokes ScheduleWork() : we are guaranteed that
- // HandleWorkMessage() will be called after entering a nested native loop that
- // should process application tasks. But once HandleWorkMessage() is out of
- // immediate work, ::SetTimer() is used to guarantee we are invoked again
- // should the next delayed task expire before the nested native loop ends. The
- // native timer being unnecessary once we return to our DoRunLoop(), we
- // ::KillTimer when it resumes (nested native loops should be rare so we're
- // not worried about ::SetTimer<=>::KillTimer churn).
- // TODO(gab): The long-standing legacy dependency on the behavior of
- // ScopedNestableTaskAllower is unfortunate, would be nice to make this a
- // MessagePump concept (instead of requiring impls to invoke ScheduleWork()
- // one-way and no-op DoWork() the other way).
- UINT delay_msec = strict_cast<UINT>(GetSleepTimeoutMs(
- next_work_info.delayed_run_time, next_work_info.recent_now));
- if (delay_msec == 0) {
- ScheduleWork();
- } else {
- // TODO(gab): ::SetTimer()'s documentation claims it does this for us.
- // Consider removing this safety net.
- delay_msec =
- clamp(delay_msec, UINT(USER_TIMER_MINIMUM), UINT(USER_TIMER_MAXIMUM));
- // Tell the optimizer to retain the delay to simplify analyzing hangs.
- base::debug::Alias(&delay_msec);
- const UINT_PTR ret =
- ::SetTimer(message_window_.hwnd(), reinterpret_cast<UINT_PTR>(this),
- delay_msec, nullptr);
- if (ret) {
- installed_native_timer_ = next_work_info.delayed_run_time;
- return;
- }
- // This error is likely similar to MESSAGE_POST_ERROR (i.e. native queue is
- // full). Since we only use ScheduleNativeTimer() in native nested loops
- // this likely means this pump will not be given a chance to run application
- // tasks until the nested loop completes.
- UMA_HISTOGRAM_ENUMERATION("Chrome.MessageLoopProblem", SET_TIMER_ERROR,
- MESSAGE_LOOP_PROBLEM_MAX);
- TRACE_EVENT_INSTANT0("base", "Chrome.MessageLoopProblem.SET_TIMER_ERROR",
- TRACE_EVENT_SCOPE_THREAD);
- }
- }
- void MessagePumpForUI::KillNativeTimer() {
- DCHECK(installed_native_timer_);
- const bool success =
- ::KillTimer(message_window_.hwnd(), reinterpret_cast<UINT_PTR>(this));
- DPCHECK(success);
- installed_native_timer_.reset();
- }
- bool MessagePumpForUI::ProcessNextWindowsMessage() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- MSG msg;
- bool has_msg = false;
- bool more_work_is_plausible = false;
- {
- // ::PeekMessage() may process sent and/or internal messages (regardless of
- // |had_messages| as ::GetQueueStatus() is an optimistic check that may
- // racily have missed an incoming event -- it doesn't hurt to have empty
- // internal units of work when ::PeekMessage turns out to be a no-op).
- // Instantiate |scoped_do_work| ahead of GetQueueStatus() so that
- // trace events it emits fully outscope GetQueueStatus' events
- // (GetQueueStatus() itself not being expected to do work; it's fine to use
- // only one ScopedDoWorkItem for both calls -- we trace them independently
- // just in case internal work stalls).
- auto scoped_do_work_item = run_state_->delegate->BeginWorkItem();
- {
- // Individually trace ::GetQueueStatus and ::PeekMessage because sampling
- // profiler is hinting that we're spending a surprising amount of time
- // with these on top of the stack. Tracing will be able to tell us whether
- // this is a bias of sampling profiler (e.g. kernel takes ::GetQueueStatus
- // as an opportunity to swap threads and is more likely to schedule the
- // sampling profiler's thread while the sampled thread is swapped out on
- // this frame).
- TRACE_EVENT0(
- TRACE_DISABLED_BY_DEFAULT("base"),
- "MessagePumpForUI::ProcessNextWindowsMessage GetQueueStatus");
- DWORD queue_status = ::GetQueueStatus(QS_SENDMESSAGE);
- // If there are sent messages in the queue then PeekMessage internally
- // dispatches the message and returns false. We return true in this case
- // to ensure that the message loop peeks again instead of calling
- // MsgWaitForMultipleObjectsEx.
- if (HIWORD(queue_status) & QS_SENDMESSAGE)
- more_work_is_plausible = true;
- }
- {
- // PeekMessage can run a message if there are sent messages, trace that
- // and emit the boolean param to see if it ever janks independently (ref.
- // comment on GetQueueStatus).
- TRACE_EVENT(
- TRACE_DISABLED_BY_DEFAULT("base"),
- "MessagePumpForUI::ProcessNextWindowsMessage PeekMessage",
- [&](perfetto::EventContext ctx) {
- perfetto::protos::pbzero::ChromeMessagePump* msg_pump_data =
- ctx.event()->set_chrome_message_pump();
- msg_pump_data->set_sent_messages_in_queue(more_work_is_plausible);
- });
- has_msg = ::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE) != FALSE;
- }
- }
- if (has_msg)
- more_work_is_plausible |= ProcessMessageHelper(msg);
- return more_work_is_plausible;
- }
- bool MessagePumpForUI::ProcessMessageHelper(const MSG& msg) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- if (msg.message == WM_QUIT) {
- // WM_QUIT is the standard way to exit a ::GetMessage() loop. Our
- // MessageLoop has its own quit mechanism, so WM_QUIT is generally
- // unexpected.
- UMA_HISTOGRAM_ENUMERATION("Chrome.MessageLoopProblem",
- RECEIVED_WM_QUIT_ERROR, MESSAGE_LOOP_PROBLEM_MAX);
- return true;
- }
- // While running our main message pump, we discard kMsgHaveWork messages.
- if (msg.message == kMsgHaveWork && msg.hwnd == message_window_.hwnd())
- return ProcessPumpReplacementMessage();
- auto scoped_do_work_item = run_state_->delegate->BeginWorkItem();
- TRACE_EVENT("base,toplevel", "MessagePumpForUI DispatchMessage",
- [&](perfetto::EventContext ctx) {
- ctx.event<perfetto::protos::pbzero::ChromeTrackEvent>()
- ->set_chrome_message_pump_for_ui()
- ->set_message_id(msg.message);
- });
- for (Observer& observer : observers_)
- observer.WillDispatchMSG(msg);
- ::TranslateMessage(&msg);
- ::DispatchMessage(&msg);
- for (Observer& observer : observers_)
- observer.DidDispatchMSG(msg);
- return true;
- }
- bool MessagePumpForUI::ProcessPumpReplacementMessage() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // When we encounter a kMsgHaveWork message, this method is called to peek and
- // process a replacement message. The goal is to make the kMsgHaveWork as non-
- // intrusive as possible, even though a continuous stream of such messages are
- // posted. This method carefully peeks a message while there is no chance for
- // a kMsgHaveWork to be pending, then resets the |have_work_| flag (allowing a
- // replacement kMsgHaveWork to possibly be posted), and finally dispatches
- // that peeked replacement. Note that the re-post of kMsgHaveWork may be
- // asynchronous to this thread!!
- MSG msg;
- bool have_message = false;
- {
- // Note: Ideally this call wouldn't process sent-messages (as we already did
- // that in the PeekMessage call that lead to receiving this kMsgHaveWork),
- // but there's no way to specify this (omitting PM_QS_SENDMESSAGE as in
- // crrev.com/791043 doesn't do anything). Hence this call must be considered
- // as a potential work item.
- TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("base"),
- "MessagePumpForUI::ProcessPumpReplacementMessage PeekMessage");
- auto scoped_do_work_item = run_state_->delegate->BeginWorkItem();
- have_message = ::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE) != FALSE;
- }
- // Expect no message or a message different than kMsgHaveWork.
- DCHECK(!have_message || kMsgHaveWork != msg.message ||
- msg.hwnd != message_window_.hwnd());
- // Since we discarded a kMsgHaveWork message, we must update the flag.
- DCHECK(work_scheduled_);
- work_scheduled_ = false;
- // We don't need a special time slice if we didn't |have_message| to process.
- if (!have_message)
- return false;
- if (msg.message == WM_QUIT) {
- // If we're in a nested ::GetMessage() loop then we must let that loop see
- // the WM_QUIT in order for it to exit. If we're in DoRunLoop then the re-
- // posted WM_QUIT will be either ignored, or handled, by
- // ProcessMessageHelper() called directly from ProcessNextWindowsMessage().
- ::PostQuitMessage(static_cast<int>(msg.wParam));
- // Note: we *must not* ScheduleWork() here as WM_QUIT is a low-priority
- // message on Windows (it is only returned by ::PeekMessage() when idle) :
- // https://blogs.msdn.microsoft.com/oldnewthing/20051104-33/?p=33453. As
- // such posting a kMsgHaveWork message via ScheduleWork() would cause an
- // infinite loop (kMsgHaveWork message handled first means we end up here
- // again and repost WM_QUIT+ScheduleWork() again, etc.). Not leaving a
- // kMsgHaveWork message behind however is also problematic as unwinding
- // multiple layers of nested ::GetMessage() loops can result in starving
- // application tasks. TODO(https://crbug.com/890016) : Fix this.
- // The return value is mostly irrelevant but return true like we would after
- // processing a QuitClosure() task.
- return true;
- } else if (msg.message == WM_TIMER &&
- msg.wParam == reinterpret_cast<UINT_PTR>(this)) {
- // This happens when a native nested loop invokes HandleWorkMessage() =>
- // ProcessPumpReplacementMessage() which finds the WM_TIMER message
- // installed by ScheduleNativeTimer(). That message needs to be handled
- // directly as handing it off to ProcessMessageHelper() below would cause an
- // unnecessary ScopedDoWorkItem which may incorrectly lead the Delegate's
- // heuristics to conclude that the DoWork() in HandleTimerMessage() is
- // nested inside a native work item. It's also safe to skip the below
- // ScheduleWork() as it is not mandatory before invoking DoWork() and
- // HandleTimerMessage() handles re-installing the necessary followup
- // messages.
- HandleTimerMessage();
- return true;
- }
- // Guarantee we'll get another time slice in the case where we go into native
- // windows code. This ScheduleWork() may hurt performance a tiny bit when
- // tasks appear very infrequently, but when the event queue is busy, the
- // kMsgHaveWork events get (percentage wise) rarer and rarer.
- ScheduleWork();
- return ProcessMessageHelper(msg);
- }
- //-----------------------------------------------------------------------------
- // MessagePumpForIO public:
- MessagePumpForIO::IOContext::IOContext() {
- memset(&overlapped, 0, sizeof(overlapped));
- }
- MessagePumpForIO::IOHandler::IOHandler(const Location& from_here)
- : io_handler_location_(from_here) {}
- MessagePumpForIO::IOHandler::~IOHandler() = default;
- MessagePumpForIO::MessagePumpForIO() {
- port_.Set(::CreateIoCompletionPort(INVALID_HANDLE_VALUE, nullptr,
- reinterpret_cast<ULONG_PTR>(nullptr), 1));
- DCHECK(port_.is_valid());
- }
- MessagePumpForIO::~MessagePumpForIO() = default;
- void MessagePumpForIO::ScheduleWork() {
- // This is the only MessagePumpForIO method which can be called outside of
- // |bound_thread_|.
- bool not_scheduled = false;
- if (!work_scheduled_.compare_exchange_strong(not_scheduled, true))
- return; // Someone else continued the pumping.
- // Make sure the MessagePump does some work for us.
- const BOOL ret = ::PostQueuedCompletionStatus(
- port_.get(), 0, reinterpret_cast<ULONG_PTR>(this),
- reinterpret_cast<OVERLAPPED*>(this));
- if (ret)
- return; // Post worked perfectly.
- // See comment in MessagePumpForUI::ScheduleWork() for this error recovery.
- work_scheduled_ = false; // Clarify that we didn't succeed.
- UMA_HISTOGRAM_ENUMERATION("Chrome.MessageLoopProblem", COMPLETION_POST_ERROR,
- MESSAGE_LOOP_PROBLEM_MAX);
- TRACE_EVENT_INSTANT0("base",
- "Chrome.MessageLoopProblem.COMPLETION_POST_ERROR",
- TRACE_EVENT_SCOPE_THREAD);
- }
- void MessagePumpForIO::ScheduleDelayedWork(
- const Delegate::NextWorkInfo& next_work_info) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // Since this is always called from |bound_thread_|, there is nothing to do as
- // the loop is already running. It will WaitForWork() in
- // DoRunLoop() with the correct timeout when it's out of immediate tasks.
- }
- HRESULT MessagePumpForIO::RegisterIOHandler(HANDLE file_handle,
- IOHandler* handler) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- HANDLE port = ::CreateIoCompletionPort(
- file_handle, port_.get(), reinterpret_cast<ULONG_PTR>(handler), 1);
- return (port != nullptr) ? S_OK : HRESULT_FROM_WIN32(GetLastError());
- }
- bool MessagePumpForIO::RegisterJobObject(HANDLE job_handle,
- IOHandler* handler) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- JOBOBJECT_ASSOCIATE_COMPLETION_PORT info;
- info.CompletionKey = handler;
- info.CompletionPort = port_.get();
- return ::SetInformationJobObject(job_handle,
- JobObjectAssociateCompletionPortInformation,
- &info, sizeof(info)) != FALSE;
- }
- //-----------------------------------------------------------------------------
- // MessagePumpForIO private:
- void MessagePumpForIO::DoRunLoop() {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- for (;;) {
- // If we do any work, we may create more messages etc., and more work may
- // possibly be waiting in another task group. When we (for example)
- // WaitForIOCompletion(), there is a good chance there are still more
- // messages waiting. On the other hand, when any of these methods return
- // having done no work, then it is pretty unlikely that calling them
- // again quickly will find any work to do. Finally, if they all say they
- // had no work, then it is a good time to consider sleeping (waiting) for
- // more work.
- Delegate::NextWorkInfo next_work_info = run_state_->delegate->DoWork();
- bool more_work_is_plausible = next_work_info.is_immediate();
- if (run_state_->should_quit)
- break;
- run_state_->delegate->BeforeWait();
- more_work_is_plausible |= WaitForIOCompletion(0);
- if (run_state_->should_quit)
- break;
- if (more_work_is_plausible)
- continue;
- more_work_is_plausible = run_state_->delegate->DoIdleWork();
- if (run_state_->should_quit)
- break;
- if (more_work_is_plausible)
- continue;
- run_state_->delegate->BeforeWait();
- WaitForWork(next_work_info);
- }
- }
- // Wait until IO completes, up to the time needed by the timer manager to fire
- // the next set of timers.
- void MessagePumpForIO::WaitForWork(Delegate::NextWorkInfo next_work_info) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- // We do not support nested IO message loops. This is to avoid messy
- // recursion problems.
- DCHECK(!run_state_->is_nested) << "Cannot nest an IO message loop!";
- DWORD timeout = GetSleepTimeoutMs(next_work_info.delayed_run_time,
- next_work_info.recent_now);
- // Tell the optimizer to retain these values to simplify analyzing hangs.
- base::debug::Alias(&timeout);
- WaitForIOCompletion(timeout);
- }
- bool MessagePumpForIO::WaitForIOCompletion(DWORD timeout) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- IOItem item;
- if (!GetIOItem(timeout, &item))
- return false;
- if (ProcessInternalIOItem(item))
- return true;
- auto scoped_do_work_item = run_state_->delegate->BeginWorkItem();
- TRACE_EVENT(
- "base,toplevel", "IOHandler::OnIOCompleted",
- [&](perfetto::EventContext ctx) {
- ctx.event()->set_chrome_message_pump()->set_io_handler_location_iid(
- base::trace_event::InternedSourceLocation::Get(
- &ctx, base::trace_event::TraceSourceLocation(
- item.handler->io_handler_location())));
- });
- item.handler->OnIOCompleted(item.context, item.bytes_transfered, item.error);
- return true;
- }
- // Asks the OS for another IO completion result.
- bool MessagePumpForIO::GetIOItem(DWORD timeout, IOItem* item) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- memset(item, 0, sizeof(*item));
- ULONG_PTR key = reinterpret_cast<ULONG_PTR>(nullptr);
- OVERLAPPED* overlapped = nullptr;
- if (!::GetQueuedCompletionStatus(port_.get(), &item->bytes_transfered, &key,
- &overlapped, timeout)) {
- if (!overlapped)
- return false; // Nothing in the queue.
- item->error = GetLastError();
- item->bytes_transfered = 0;
- }
- item->handler = reinterpret_cast<IOHandler*>(key);
- item->context = reinterpret_cast<IOContext*>(overlapped);
- return true;
- }
- bool MessagePumpForIO::ProcessInternalIOItem(const IOItem& item) {
- DCHECK_CALLED_ON_VALID_THREAD(bound_thread_);
- if (reinterpret_cast<void*>(this) ==
- reinterpret_cast<void*>(item.context.get()) &&
- reinterpret_cast<void*>(this) ==
- reinterpret_cast<void*>(item.handler.get())) {
- // This is our internal completion.
- DCHECK(!item.bytes_transfered);
- work_scheduled_ = false;
- return true;
- }
- return false;
- }
- } // namespace base
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