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fix: EventLoop::post() deadlocks when posted function throws #260

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fix: EventLoop::post() deadlocks when posted function throws #260

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24 changes: 20 additions & 4 deletions src/mp/proxy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,12 @@ EventLoop::~EventLoop()
{
if (m_async_thread.joinable()) m_async_thread.join();
const Lock lock(m_mutex);

if (m_post_fd != -1) {
KJ_SYSCALL(::close(m_post_fd));
m_post_fd = -1;
}

KJ_ASSERT(m_post_fn == nullptr);
KJ_ASSERT(!m_async_fns);
KJ_ASSERT(m_wait_fd == -1);
Expand All @@ -239,13 +245,26 @@ void EventLoop::loop()
kj::Own<kj::AsyncIoStream> wait_stream{
m_io_context.lowLevelProvider->wrapSocketFd(m_wait_fd, kj::LowLevelAsyncIoProvider::TAKE_OWNERSHIP)};
int post_fd{m_post_fd};
KJ_DEFER({
Lock lock(m_mutex);
m_cv.wait(lock.m_lock, [this]() MP_REQUIRES(m_mutex) { return m_num_clients == 0; });
m_wait_fd = -1;
m_async_fns.reset();
m_cv.notify_all();
});
char buffer = 0;
for (;;) {
const size_t read_bytes = wait_stream->read(&buffer, 0, 1).wait(m_io_context.waitScope);
if (read_bytes != 1) throw std::logic_error("EventLoop wait_stream closed unexpectedly");
Lock lock(m_mutex);
if (m_post_fn) {
Unlock(lock, *m_post_fn);
try {
Unlock(lock, *m_post_fn);
} catch (...) {
m_post_fn = nullptr;
m_cv.notify_all();
throw;
}
m_post_fn = nullptr;
m_cv.notify_all();
} else if (done()) {
Expand All @@ -262,10 +281,7 @@ void EventLoop::loop()
wait_stream = nullptr;
KJ_SYSCALL(::close(post_fd));
const Lock lock(m_mutex);
m_wait_fd = -1;
m_post_fd = -1;
m_async_fns.reset();
m_cv.notify_all();
}

void EventLoop::post(kj::Function<void()> fn)
Expand Down