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/* -*- 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 "mozilla/mscom/MainThreadInvoker.h"
#include "GeckoProfiler.h"
#include "MainThreadUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/HangMonitor.h"
#include "mozilla/RefPtr.h"
#include "nsServiceManagerUtils.h"
#include "nsSystemInfo.h"
#include "private/prpriv.h" // For PR_GetThreadID
#include "WinUtils.h"
// This gives us compiler intrinsics for the x86 PAUSE instruction
#if defined(_MSC_VER)
#include <intrin.h>
#pragma intrinsic(_mm_pause)
#define CPU_PAUSE() _mm_pause()
#elif defined(__GNUC__) || defined(__clang__)
#define CPU_PAUSE() __builtin_ia32_pause()
#endif
static bool sIsMulticore;
namespace {
/**
* SyncRunnable implements different code paths depending on whether or not
* we are running on a multiprocessor system. In the multiprocessor case, we
* leave the thread in a spin loop while waiting for the main thread to execute
* our runnable. Since spinning is pointless in the uniprocessor case, we block
* on an event that is set by the main thread once it has finished the runnable.
*/
class MOZ_RAII SyncRunnable
{
public:
explicit SyncRunnable(already_AddRefed<nsIRunnable>&& aRunnable)
: mDoneEvent(sIsMulticore ? nullptr :
::CreateEventW(nullptr, FALSE, FALSE, nullptr))
, mDone(false)
, mRunnable(aRunnable)
{
MOZ_ASSERT(sIsMulticore || mDoneEvent);
MOZ_ASSERT(mRunnable);
}
~SyncRunnable()
{
if (mDoneEvent) {
::CloseHandle(mDoneEvent);
}
}
void Run()
{
mRunnable->Run();
if (mDoneEvent) {
::SetEvent(mDoneEvent);
} else {
mDone = true;
}
}
bool WaitUntilComplete()
{
if (mDoneEvent) {
HANDLE handles[] = {mDoneEvent,
mozilla::mscom::MainThreadInvoker::GetTargetThread()};
DWORD waitResult = ::WaitForMultipleObjects(mozilla::ArrayLength(handles),
handles, FALSE, INFINITE);
return waitResult == WAIT_OBJECT_0;
}
while (!mDone) {
// The PAUSE instruction is a hint to the CPU that we're doing a spin
// loop. It is a no-op on older processors that don't support it, so
// it is safe to use here without any CPUID checks.
CPU_PAUSE();
}
return true;
}
private:
HANDLE mDoneEvent;
mozilla::Atomic<bool> mDone;
nsCOMPtr<nsIRunnable> mRunnable;
};
} // anonymous namespace
namespace mozilla {
namespace mscom {
HANDLE MainThreadInvoker::sMainThread = nullptr;
/* static */ bool
MainThreadInvoker::InitStatics()
{
nsCOMPtr<nsIThread> mainThread;
nsresult rv = ::NS_GetMainThread(getter_AddRefs(mainThread));
if (NS_FAILED(rv)) {
return false;
}
PRThread* mainPrThread = nullptr;
rv = mainThread->GetPRThread(&mainPrThread);
if (NS_FAILED(rv)) {
return false;
}
PRUint32 tid = ::PR_GetThreadID(mainPrThread);
sMainThread = ::OpenThread(SYNCHRONIZE | THREAD_SET_CONTEXT, FALSE, tid);
nsCOMPtr<nsIPropertyBag2> infoService = do_GetService(NS_SYSTEMINFO_CONTRACTID);
if (infoService) {
uint32_t cpuCount;
nsresult rv = infoService->GetPropertyAsUint32(NS_LITERAL_STRING("cpucount"),
&cpuCount);
sIsMulticore = NS_SUCCEEDED(rv) && cpuCount > 1;
}
return !!sMainThread;
}
MainThreadInvoker::MainThreadInvoker()
{
static const bool gotStatics = InitStatics();
MOZ_ASSERT(gotStatics);
}
bool
MainThreadInvoker::Invoke(already_AddRefed<nsIRunnable>&& aRunnable)
{
nsCOMPtr<nsIRunnable> runnable(Move(aRunnable));
if (!runnable) {
return false;
}
if (NS_IsMainThread()) {
runnable->Run();
return true;
}
SyncRunnable syncRunnable(runnable.forget());
if (!::QueueUserAPC(&MainThreadAPC, sMainThread,
reinterpret_cast<UINT_PTR>(&syncRunnable))) {
return false;
}
// We should ensure a call to NtTestAlert() is made on the main thread so
// that the main thread will check for APCs during event processing. If we
// omit this then the main thread will not check its APC queue until it is
// idle.
widget::WinUtils::SetAPCPending();
return syncRunnable.WaitUntilComplete();
}
/* static */ VOID CALLBACK
MainThreadInvoker::MainThreadAPC(ULONG_PTR aParam)
{
GeckoProfilerWakeRAII wakeProfiler;
mozilla::HangMonitor::NotifyActivity(mozilla::HangMonitor::kGeneralActivity);
MOZ_ASSERT(NS_IsMainThread());
auto runnable = reinterpret_cast<SyncRunnable*>(aParam);
runnable->Run();
}
} // namespace mscom
} // namespace mozilla
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