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f5bdb858e0
Moved all the threading code to one place. Added explicit support for Darwin, Linux, Pthreads, C11 threads and Win32 threads, including new implementations of Once for Linux, Pthreads, C11 and Win32. rdar://90776105
104 lines
3.0 KiB
C++
104 lines
3.0 KiB
C++
//==--- Win32.cpp - Threading abstraction implementation ------- -*-C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2022 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// Implements threading support for Windows threads
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//
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//===----------------------------------------------------------------------===//
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#if SWIFT_THREADING_WIN32
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#include "swift/Threading/Errors.h"
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#include "swift/Threading/Impl/Win32.h"
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namespace {
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#pragma clang diagnostic push
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#pragma GCC diagnostic ignored "-Wglobal-constructors"
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class MainThreadRememberer {
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private:
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DWORD dwMainThread_;
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public:
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MainThreadRememberer() { dwMainThread_ = ::GetCurrentThreadId(); }
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DWORD main_thread() const { return dwMainThread_; }
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};
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MainThreadRememberer rememberer;
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// Prior to Windows 8, we have to use a global lock
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#if _WIN32_WINNT < 0x0602
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SRWLOCK onceMutex = SRWLOCK_INIT;
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CONDITION_VARIABLE onceCond = CONDITION_VARIABLE_INIT;
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#endif
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#pragma clang diagnostic pop
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}
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using namespace swift;
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using namespace threading_impl;
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thread_id
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swift::threading_impl::thread_get_main() {
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return rememberer.main_thread();
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}
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bool
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swift::threading_impl::thread_is_main() {
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return ::GetCurrentThreadId() == thread_get_main();
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}
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void
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swift::threading_impl::once_slow(once_t &predicate,
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void (*fn)(void *),
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void *context) {
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std::int64_t expected = 0;
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if (predicate.compare_exchange_strong(expected, (std::int64_t)1,
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std::memory_order_relaxed,
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std::memory_order_relaxed)) {
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fn(context);
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predicate.store((std::int64_t)-1, std::memory_order_release);
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#if _WIN32_WINNT >= 0x0602
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// On Windows 8, use WakeByAddressAll() to wake waiters
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WakeByAddressAll(&predicate);
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#else
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// On Windows 7 and earlier, we use a global lock and condition variable;
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// this will wake *all* waiters on *all* onces, which might result in a
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// thundering herd problem, but it's the best we can do.
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AcquireSRWLockExclusive(&onceMutex);
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WakeAllConditionVariable(&onceCond);
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ReleaseSRWLockExclusive(&onceMutex);
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#endif
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return;
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}
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#if _WIN32_WINNT >= 0x0602
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// On Windows 8, loop waiting on the address until it changes to -1
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while (expected >= 0) {
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WaitOnAddress(&predicate, &expected, 8, INFINITE);
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expected = predicate.load(std::memory_order_acquire);
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}
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#else
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// On Windows 7 and earlier, wait on the global condition variable
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AcquireSRWLockExclusive(&onceMutex);
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while (predicate.load(std::memory_order_acquire) >= 0) {
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SleepConditionVariableSRW(&onceCond, &onceMutex, INFINITE, 0);
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}
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ReleaseSRWLockExclusive(&onceMutex);
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#endif
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}
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#endif // SWIFT_THREADING_WIN32
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