From 3fdb42e0b483769648142e5994ea7766bddfc077 Mon Sep 17 00:00:00 2001 From: ReinUsesLisp Date: Wed, 28 Oct 2020 01:33:57 -0300 Subject: [PATCH] tests: Fix data race in fibers test Previous to this commit, the tests were using operator[] from unordered_map to query elements but this silently inserts empty elements when they don't exist. If all threads were executed without concurrency, this wouldn't be an issue, but the same unordered_map could be written from two threads at the same time. This is a data race and makes some previously inserted elements invisible for a short period of time, causing them to insert and return an empty element. This default constructed element (a zero) was used to index an array of fibers that asserted when one of them was nullptr, shutting the test session off. To address this issue, lock on thread id reads and writes. This could be a shared mutex to allow concurrent reads, but the definition of std::this_thread::get_id is fuzzy when using non-standard techniques like fibers. I opted to use a standard mutex. While we are at it, fix the included headers. --- src/tests/common/fibers.cpp | 71 +++++++++++++++++++++---------------- 1 file changed, 40 insertions(+), 31 deletions(-) diff --git a/src/tests/common/fibers.cpp b/src/tests/common/fibers.cpp index 4fd92428f..4757dd2b4 100644 --- a/src/tests/common/fibers.cpp +++ b/src/tests/common/fibers.cpp @@ -6,18 +6,40 @@ #include #include #include +#include +#include #include #include #include #include -#include + #include "common/common_types.h" #include "common/fiber.h" -#include "common/spin_lock.h" namespace Common { +class ThreadIds { +public: + void Register(u32 id) { + const auto thread_id = std::this_thread::get_id(); + std::scoped_lock lock{mutex}; + if (ids.contains(thread_id)) { + throw std::logic_error{"Registering the same thread twice"}; + } + ids.emplace(thread_id, id); + } + + [[nodiscard]] u32 Get() const { + std::scoped_lock lock{mutex}; + return ids.at(std::this_thread::get_id()); + } + +private: + mutable std::mutex mutex; + std::unordered_map ids; +}; + class TestControl1 { public: TestControl1() = default; @@ -26,7 +48,7 @@ public: void ExecuteThread(u32 id); - std::unordered_map ids; + ThreadIds thread_ids; std::vector> thread_fibers; std::vector> work_fibers; std::vector items; @@ -39,8 +61,7 @@ static void WorkControl1(void* control) { } void TestControl1::DoWork() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); u32 value = items[id]; for (u32 i = 0; i < id; i++) { value++; @@ -50,8 +71,7 @@ void TestControl1::DoWork() { } void TestControl1::ExecuteThread(u32 id) { - std::thread::id this_id = std::this_thread::get_id(); - ids[this_id] = id; + thread_ids.Register(id); auto thread_fiber = Fiber::ThreadToFiber(); thread_fibers[id] = thread_fiber; work_fibers[id] = std::make_shared(std::function{WorkControl1}, this); @@ -98,8 +118,7 @@ public: value1 += i; } Fiber::YieldTo(fiber1, fiber3); - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); assert1 = id == 1; value2 += 5000; Fiber::YieldTo(fiber1, thread_fibers[id]); @@ -115,8 +134,7 @@ public: } void DoWork3() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); assert2 = id == 0; value1 += 1000; Fiber::YieldTo(fiber3, thread_fibers[id]); @@ -125,14 +143,12 @@ public: void ExecuteThread(u32 id); void CallFiber1() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); Fiber::YieldTo(thread_fibers[id], fiber1); } void CallFiber2() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); Fiber::YieldTo(thread_fibers[id], fiber2); } @@ -145,7 +161,7 @@ public: u32 value2{}; std::atomic trap{true}; std::atomic trap2{true}; - std::unordered_map ids; + ThreadIds thread_ids; std::vector> thread_fibers; std::shared_ptr fiber1; std::shared_ptr fiber2; @@ -168,15 +184,13 @@ static void WorkControl2_3(void* control) { } void TestControl2::ExecuteThread(u32 id) { - std::thread::id this_id = std::this_thread::get_id(); - ids[this_id] = id; + thread_ids.Register(id); auto thread_fiber = Fiber::ThreadToFiber(); thread_fibers[id] = thread_fiber; } void TestControl2::Exit() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); thread_fibers[id]->Exit(); } @@ -228,24 +242,21 @@ public: void DoWork1() { value1 += 1; Fiber::YieldTo(fiber1, fiber2); - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); value3 += 1; Fiber::YieldTo(fiber1, thread_fibers[id]); } void DoWork2() { value2 += 1; - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); Fiber::YieldTo(fiber2, thread_fibers[id]); } void ExecuteThread(u32 id); void CallFiber1() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); Fiber::YieldTo(thread_fibers[id], fiber1); } @@ -254,7 +265,7 @@ public: u32 value1{}; u32 value2{}; u32 value3{}; - std::unordered_map ids; + ThreadIds thread_ids; std::vector> thread_fibers; std::shared_ptr fiber1; std::shared_ptr fiber2; @@ -271,15 +282,13 @@ static void WorkControl3_2(void* control) { } void TestControl3::ExecuteThread(u32 id) { - std::thread::id this_id = std::this_thread::get_id(); - ids[this_id] = id; + thread_ids.Register(id); auto thread_fiber = Fiber::ThreadToFiber(); thread_fibers[id] = thread_fiber; } void TestControl3::Exit() { - std::thread::id this_id = std::this_thread::get_id(); - u32 id = ids[this_id]; + const u32 id = thread_ids.Get(); thread_fibers[id]->Exit(); }