event/Loop: pass timeout=nullptr to io_uring if there is no timer

src/event/Loop.cxx

@@ -297,23 +297,25 @@ ExportTimeoutMS(Event::Duration timeout) noexcept
 
 #ifdef HAVE_URING
 
-static constexpr struct __kernel_timespec
-ExportTimeoutKernelTimespec(Event::Duration timeout) noexcept
+static struct __kernel_timespec *
+ExportTimeoutKernelTimespec(Event::Duration timeout, struct __kernel_timespec &buffer) noexcept
 {
 	if (timeout < timeout.zero())
-		// TODO if there is no time, there should be no timeout at all
-		return { .tv_sec = 24 * 3600 };
+		return nullptr;
 
-	if (timeout >= std::chrono::duration_cast<Event::Duration>(std::chrono::hours{24})) [[unlikely]]
-		return {
+	if (timeout >= std::chrono::duration_cast<Event::Duration>(std::chrono::hours{24})) [[unlikely]] {
+		buffer = {
 			.tv_sec = std::chrono::ceil<std::chrono::duration<__kernel_time64_t>>(timeout).count(),
 		};
+		return &buffer;
+	}
 
 	const auto nsec = std::chrono::ceil<std::chrono::nanoseconds>(timeout);
-	return {
+	buffer = {
 		.tv_sec = nsec.count() / 1000000000,
 		.tv_nsec = nsec.count() % 1000000000,
 	};
+	return &buffer;
 }
 
 #endif
@@ -424,7 +426,8 @@ EventLoop::Run() noexcept
 			   consume all events to rearm it */
 
 			if (!epoll_ready) {
-				auto kernel_timeout = ExportTimeoutKernelTimespec(timeout);
+				struct __kernel_timespec timeout_buffer;
+				auto *kernel_timeout = ExportTimeoutKernelTimespec(timeout, timeout_buffer);
 				Uring::Queue &uring_queue = *uring;
 				uring_queue.SubmitAndWaitDispatchCompletions(kernel_timeout);
 			}

src/io/uring/Queue.cxx

@@ -104,7 +104,7 @@ Queue::WaitDispatchOneCompletion()
 }
 
 bool
-Queue::SubmitAndWaitDispatchCompletions(struct __kernel_timespec &timeout)
+Queue::SubmitAndWaitDispatchCompletions(struct __kernel_timespec *timeout)
 {
 	auto *cqe = ring.SubmitAndWaitCompletion(timeout);
 	if (cqe == nullptr)

src/io/uring/Queue.hxx

@@ -101,7 +101,7 @@ public:
 		while (WaitDispatchOneCompletion()) {}
 	}
 
-	bool SubmitAndWaitDispatchCompletions(struct __kernel_timespec &timeout);
+	bool SubmitAndWaitDispatchCompletions(struct __kernel_timespec *timeout);
 
 private:
 	static void _DispatchOneCompletion(const struct io_uring_cqe &cqe) noexcept;

src/io/uring/Ring.cxx

@@ -61,10 +61,10 @@ Ring::WaitCompletion()
 }
 
 struct io_uring_cqe *
-Ring::SubmitAndWaitCompletion(struct __kernel_timespec &timeout)
+Ring::SubmitAndWaitCompletion(struct __kernel_timespec *timeout)
 {
 	struct io_uring_cqe *cqe;
-	if (int error = io_uring_submit_and_wait_timeout(&ring, &cqe, 1, &timeout, nullptr);
+	if (int error = io_uring_submit_and_wait_timeout(&ring, &cqe, 1, timeout, nullptr);
 	    error < 0) {
 		if (error == -ETIME || error == -EAGAIN || error == -EINTR)
 			return nullptr;

src/io/uring/Ring.hxx

@@ -109,7 +109,7 @@ public:
 	 *
 	 * @return a completion queue entry or nullptr on EAGAIN/ETIME
 	 */
-	struct io_uring_cqe *SubmitAndWaitCompletion(struct __kernel_timespec &timeout);
+	struct io_uring_cqe *SubmitAndWaitCompletion(struct __kernel_timespec *timeout);
 
 	/**
 	 * Peek one completion (non-blocking).