| 1 | // RUN: %clangxx_tsan -O1 %s %link_libcxx_tsan -o %t && %run %t 2>&1 |
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| 2 | // This is a correct program and tsan should not report a race. |
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| 3 | // |
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| 4 | // Verify that there is a happens-before relationship between a |
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| 5 | // memory_order_release store that happens as part of a successful |
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| 6 | // compare_exchange_strong(), and an atomic_thread_fence(memory_order_acquire) |
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| 7 | // that happens after a relaxed load. |
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| 8 | |
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| 9 | #include <atomic> |
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| 10 | #include <sanitizer/tsan_interface.h> |
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| 11 | #include <stdbool.h> |
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| 12 | #include <stdio.h> |
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| 13 | #include <thread> |
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| 14 | |
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| 15 | std::atomic<bool> a; |
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| 16 | unsigned int b; |
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| 17 | constexpr int loops = 100000; |
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| 18 | |
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| 19 | void Thread1() { |
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| 20 | for (int i = 0; i < loops; ++i) { |
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| 21 | while (a.load(std::memory_order_acquire)) { |
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| 22 | } |
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| 23 | b = i; |
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| 24 | bool expected = false; |
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| 25 | a.compare_exchange_strong(expected, true, std::memory_order_acq_rel); |
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| 26 | } |
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| 27 | } |
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| 28 | |
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| 29 | int main() { |
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| 30 | std::thread t(Thread1); |
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| 31 | unsigned int sum = 0; |
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| 32 | for (int i = 0; i < loops; ++i) { |
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| 33 | while (!a.load(std::memory_order_relaxed)) { |
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| 34 | } |
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| 35 | std::atomic_thread_fence(std::memory_order_acquire); |
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| 36 | __tsan_acquire(&a); |
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| 37 | sum += b; |
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| 38 | a.store(false, std::memory_order_release); |
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| 39 | } |
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| 40 | t.join(); |
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| 41 | fprintf(stderr, format: "DONE: %u\n" , sum); |
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| 42 | return 0; |
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| 43 | } |
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| 44 | |
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