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[libc++] Remove race condition in std::async
Summary: The state associated to the future was set in one thread (with synchronization) but read in another thread without synchronization, which led to a data race. https://bugs.llvm.org/show_bug.cgi?id=38181 rdar://problem/42548261 Reviewers: mclow.lists, EricWF Subscribers: christof, dexonsmith, cfe-commits Differential Revision: https://reviews.llvm.org/D51170 llvm-svn: 340608
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libcxx/test/std/thread/futures/futures.async/async_race.38682.pass.cpp
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//===----------------------------------------------------------------------===// | ||
// | ||
// The LLVM Compiler Infrastructure | ||
// | ||
// This file is dual licensed under the MIT and the University of Illinois Open | ||
// Source Licenses. See LICENSE.TXT for details. | ||
// | ||
//===----------------------------------------------------------------------===// | ||
// | ||
// UNSUPPORTED: libcpp-has-no-threads | ||
// UNSUPPORTED: c++98, c++03 | ||
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// This test is designed to cause and allow TSAN to detect a race condition | ||
// in std::async, as reported in https://bugs.llvm.org/show_bug.cgi?id=38682. | ||
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#include <cassert> | ||
#include <functional> | ||
#include <future> | ||
#include <numeric> | ||
#include <vector> | ||
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static int worker(std::vector<int> const& data) { | ||
return std::accumulate(data.begin(), data.end(), 0); | ||
} | ||
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static int& worker_ref(int& i) { return i; } | ||
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static void worker_void() { } | ||
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int main() { | ||
// future<T> | ||
{ | ||
std::vector<int> const v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; | ||
for (int i = 0; i != 20; ++i) { | ||
std::future<int> fut = std::async(std::launch::async, worker, v); | ||
int answer = fut.get(); | ||
assert(answer == 55); | ||
} | ||
} | ||
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// future<T&> | ||
{ | ||
for (int i = 0; i != 20; ++i) { | ||
std::future<int&> fut = std::async(std::launch::async, worker_ref, std::ref(i)); | ||
int& answer = fut.get(); | ||
assert(answer == i); | ||
} | ||
} | ||
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// future<void> | ||
{ | ||
for (int i = 0; i != 20; ++i) { | ||
std::future<void> fut = std::async(std::launch::async, worker_void); | ||
fut.get(); | ||
} | ||
} | ||
} |