diff --git a/examples/sync-primitive/sync-primitive.cpp b/examples/sync-primitive/sync-primitive.cpp
index 61977b9a..173e8ea4 100644
--- a/examples/sync-primitive/sync-primitive.cpp
+++ b/examples/sync-primitive/sync-primitive.cpp
@@ -43,7 +43,7 @@ struct Message {
     std::chrono::time_point<std::chrono::steady_clock> start;
 };
 
-static const int num_producers = 16, num_consumers = 16;
+static const int num_producers = 8, num_consumers = 8;
 static LockfreeMPMCRingQueue<Message*, 1024 * 1024> ring;
 static std::atomic<uint64_t> qps{0}, latency{0};
 
@@ -90,7 +90,7 @@ int main() {
                 Message message;
                 ring.push(&message);
                 {
-                    std::unique_lock l(message.mu);
+                    std::unique_lock<std::mutex> l(message.mu);
                     message.cv.wait(l, [&] { return message.done; });
                 }
                 auto end = std::chrono::steady_clock::now();
@@ -117,7 +117,7 @@ int main() {
                 m->sem.signal(1);
 #else
                 {
-                    std::unique_lock l(m->mu);
+                    std::unique_lock<std::mutex> l(m->mu);
                     m->done = true;
                     m->cv.notify_one();
                 }
@@ -128,7 +128,6 @@ int main() {
 
     // Show QPS and latency
     photon::thread_create11([&] {
-        photon::init(photon::INIT_EVENT_DEFAULT, photon::INIT_IO_NONE);
         while (true) {
             photon::thread_sleep(1);
             auto prev_qps = qps.exchange(0, std::memory_order_seq_cst);
diff --git a/io/iouring-wrapper.cpp b/io/iouring-wrapper.cpp
index d0e29059..77579daa 100644
--- a/io/iouring-wrapper.cpp
+++ b/io/iouring-wrapper.cpp
@@ -133,7 +133,7 @@ class iouringEngine : public MasterEventEngine, public CascadingEventEngine, pub
             }
         }
 
-        m_eventfd = eventfd(0, EFD_CLOEXEC);
+        m_eventfd = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
         if (m_eventfd < 0) {
             LOG_ERRNO_RETURN(0, -1, "iouring: failed to create eventfd");
         }
@@ -285,10 +285,8 @@ class iouringEngine : public MasterEventEngine, public CascadingEventEngine, pub
         if (ret < 0) {
             return errno == ETIMEDOUT ? 0 : -1;
         }
-        uint64_t value = 0;
-        if (eventfd_read(m_eventfd, &value)) {
-            LOG_ERROR("iouring: error reading cascading event fd, `", ERRNO());
-        }
+        uint64_t value;
+        eventfd_read(m_eventfd, &value);
 
         // Reap events
         size_t num = 0;
diff --git a/rpc/serialize.h b/rpc/serialize.h
index 0aa327bd..df5763db 100644
--- a/rpc/serialize.h
+++ b/rpc/serialize.h
@@ -71,6 +71,7 @@ namespace rpc
         const T& operator[](long i) const { return ((T*)_ptr)[i]; }
         const T& front() const    { return (*this)[0]; }
         const T& back() const     { return (*this)[(long)size() - 1]; }
+        bool empty() const { return _len == 0; }
         void assign(const T* x, size_t size) { buffer::assign(x, sizeof(*x) * size); }
         void assign(const std::vector<T>& vec) { assign(&vec[0], vec.size()); }
 
diff --git a/thread/std-compat.h b/thread/std-compat.h
index 91c56b5d..a71a3b18 100644
--- a/thread/std-compat.h
+++ b/thread/std-compat.h
@@ -222,9 +222,10 @@ class unique_lock {
     }
 
     Mutex* release() noexcept {
+        auto* mu = m_mutex;
         m_mutex = nullptr;
         m_owns = false;
-        return m_mutex;
+        return mu;
     }
 
     Mutex* mutex() const noexcept {