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0b4ea77880
The implementation mistakenly locked and unlocked the mutex in `helper.once_wait()`, which is only ever called from inside a region where the mutex is already locked. rdar://119739594
89 lines
2.5 KiB
C++
89 lines
2.5 KiB
C++
//==--- C11.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 C11 threads
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//
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//===----------------------------------------------------------------------===//
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#if SWIFT_THREADING_C11
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#include "swift/Threading/Impl.h"
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#include "swift/Threading/Errors.h"
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namespace {
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Wglobal-constructors"
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class C11ThreadingHelper {
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private:
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thrd_t mainThread_;
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mtx_t onceMutex_;
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cnd_t onceCond_;
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public:
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C11ThreadingHelper() {
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mainThread_ = thrd_current();
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SWIFT_C11THREADS_CHECK(::mtx_init(&onceMutex_, ::mtx_plain));
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SWIFT_C11THREADS_CHECK(::cnd_init(&onceCond_));
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}
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thrd_t main_thread() const { return mainThread_; }
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void once_lock() { SWIFT_C11THREADS_CHECK(mtx_lock(&onceMutex_)); }
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void once_unlock() { SWIFT_C11THREADS_CHECK(mtx_unlock(&onceMutex_)); }
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void once_broadcast() { SWIFT_C11THREADS_CHECK(cnd_broadcast(&onceCond_)); }
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void once_wait() {
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// The mutex must be locked when this function is entered. It will
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// be locked again before the function returns.
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SWIFT_C11THREADS_CHECK(cnd_wait(&onceCond_, &onceMutex_));
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}
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};
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C11ThreadingHelper helper;
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#pragma clang diagnostic pop
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} // namespace
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using namespace swift;
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using namespace threading_impl;
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bool swift::threading_impl::thread_is_main() {
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return thrd_equal(thrd_current(), helper.main_thread());
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}
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void swift::threading_impl::once_slow(once_t &predicate, void (*fn)(void *),
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void *context) {
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std::intptr_t zero = 0;
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if (predicate.compare_exchange_strong(zero, (std::intptr_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::intptr_t)-1, std::memory_order_release);
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helper.once_lock();
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helper.once_unlock();
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helper.once_broadcast();
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return;
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}
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helper.once_lock();
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while (predicate.load(std::memory_order_acquire) >= (std::intptr_t)0) {
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helper.once_wait();
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}
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helper.once_unlock();
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}
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#endif // SWIFT_THREADING_C11
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