1e5f275f36
This refactoring is done to remove flakyness as described in https://github.com/llvm/llvm-project/pull/89083.
111 lines
2.6 KiB
C++
111 lines
2.6 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03
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// UNSUPPORTED: no-threads
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// <mutex>
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// class recursive_mutex;
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// void lock();
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#include <mutex>
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#include <atomic>
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#include <cassert>
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#include <thread>
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#include <vector>
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#include "make_test_thread.h"
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bool is_lockable(std::recursive_mutex& m) {
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bool did_lock;
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std::thread t = support::make_test_thread([&] {
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did_lock = m.try_lock();
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if (did_lock)
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m.unlock(); // undo side effects
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});
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t.join();
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return did_lock;
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}
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int main(int, char**) {
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// Lock a mutex that is not locked yet. This should succeed.
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{
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std::recursive_mutex m;
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m.lock();
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m.unlock();
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}
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// Lock a mutex that is already locked by this thread. This should succeed and the mutex should only
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// be unlocked after a matching number of calls to unlock() on the same thread.
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{
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std::recursive_mutex m;
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int lock_count = 0;
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for (int i = 0; i != 10; ++i) {
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m.lock();
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++lock_count;
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}
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while (lock_count != 0) {
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assert(!is_lockable(m));
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m.unlock();
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--lock_count;
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}
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assert(is_lockable(m));
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}
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// Lock a mutex that is already locked by another thread. This should block until it is unlocked.
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{
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std::atomic<bool> ready(false);
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std::recursive_mutex m;
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m.lock();
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std::atomic<bool> is_locked_from_main(true);
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std::thread t = support::make_test_thread([&] {
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ready = true;
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m.lock();
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assert(!is_locked_from_main);
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m.unlock();
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});
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while (!ready)
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/* spin */;
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// We would rather signal this after we unlock, but that would create a race condition.
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// We instead signal it before we unlock, which means that it's technically possible for
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// the thread to take the lock while main is still holding it yet for the test to still pass.
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is_locked_from_main = false;
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m.unlock();
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t.join();
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}
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// Make sure that at most one thread can acquire the mutex concurrently.
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{
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std::atomic<int> counter(0);
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std::recursive_mutex mutex;
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std::vector<std::thread> threads;
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for (int i = 0; i != 10; ++i) {
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threads.push_back(support::make_test_thread([&] {
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mutex.lock();
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counter++;
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assert(counter == 1);
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counter--;
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mutex.unlock();
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}));
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}
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for (auto& t : threads)
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t.join();
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}
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return 0;
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}
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