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//==--- Win32.cpp - Threading abstraction implementation ------- -*-C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// Implements threading support for Windows threads
//
//===----------------------------------------------------------------------===//
#if SWIFT_THREADING_WIN32
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <windows.h>
#include "swift/Threading/Errors.h"
#include "swift/Threading/Impl.h"
namespace {
#pragma clang diagnostic push
#pragma GCC diagnostic ignored "-Wglobal-constructors"
class MainThreadRememberer {
private:
DWORD dwMainThread_;
public:
MainThreadRememberer() { dwMainThread_ = ::GetCurrentThreadId(); }
DWORD main_thread() const { return dwMainThread_; }
};
MainThreadRememberer rememberer;
// Prior to Windows 8, we have to use a global lock
#if _WIN32_WINNT < 0x0602
SRWLOCK onceMutex = SRWLOCK_INIT;
CONDITION_VARIABLE onceCond = CONDITION_VARIABLE_INIT;
#endif
#pragma clang diagnostic pop
} // namespace
using namespace swift;
using namespace threading_impl;
bool swift::threading_impl::thread_is_main() {
return ::GetCurrentThreadId() == rememberer.main_thread();
}
void swift::threading_impl::once_slow(once_t &predicate, void (*fn)(void *),
void *context) {
intptr_t expected = 0;
if (predicate.compare_exchange_strong(expected, static_cast<intptr_t>(1),
std::memory_order_relaxed,
std::memory_order_relaxed)) {
fn(context);
predicate.store(static_cast<intptr_t>(-1), std::memory_order_release);
#if _WIN32_WINNT >= 0x0602
// On Windows 8, use WakeByAddressAll() to wake waiters
WakeByAddressAll(&predicate);
#else
// On Windows 7 and earlier, we use a global lock and condition variable;
// this will wake *all* waiters on *all* onces, which might result in a
// thundering herd problem, but it's the best we can do.
AcquireSRWLockExclusive(&onceMutex);
WakeAllConditionVariable(&onceCond);
ReleaseSRWLockExclusive(&onceMutex);
#endif
return;
}
#if _WIN32_WINNT >= 0x0602
// On Windows 8, loop waiting on the address until it changes to -1
while (expected >= 0) {
WaitOnAddress(&predicate, &expected, sizeof(expected), INFINITE);
expected = predicate.load(std::memory_order_acquire);
}
#else
// On Windows 7 and earlier, wait on the global condition variable
AcquireSRWLockExclusive(&onceMutex);
while (predicate.load(std::memory_order_acquire) >= 0) {
SleepConditionVariableSRW(&onceCond, &onceMutex, INFINITE, 0);
}
ReleaseSRWLockExclusive(&onceMutex);
#endif
}
std::optional<swift::threading_impl::stack_bounds>
swift::threading_impl::thread_get_current_stack_bounds() {
#if _WIN32_WINNT >= 0x0602
ULONG_PTR lowLimit = 0;
ULONG_PTR highLimit = 0;
GetCurrentThreadStackLimits(&lowLimit, &highLimit);
stack_bounds result = { (void *)lowLimit, (void *)highLimit };
#else
MEMORY_BASIC_INFORMATION mbi;
VirtualQuery(&mbi, &mbi, sizeof(mbi));
stack_bounds result = {
mbi.AllocationBase,
(char *)mbi.BaseAddress + mbi.RegionSize
};
#endif
return result;
}
#endif // SWIFT_THREADING_WIN32
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