diff --git a/CMakeLists.txt b/CMakeLists.txt
index 59a083b..ab75262 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -204,7 +204,7 @@ if((NOT TILE_HAVE_GETIFADDRS) OR (NOT TILE_HAVE_FREEIFADDRS))
   list(APPEND TILE_SRCS "tile/base/net/detail/android/ifaddrs.c")
 endif()
 
-add_library(tile OBJECT ${TILE_SRCS} ${ASM_SRCS})
+add_library(tile OBJECT ${TILE_SRCS})
 set_target_properties(tile PROPERTIES VERSION ${PROJECT_VERSION}
                                       SOVERSION "${tile_VERSION_MAJRO}")
 # target_sources(tile PRIVATE ${TILE_SRCS})
diff --git a/third_party/context/CMakeLists.txt b/third_party/context/CMakeLists.txt
index 5174108..cf8db97 100644
--- a/third_party/context/CMakeLists.txt
+++ b/third_party/context/CMakeLists.txt
@@ -10,7 +10,7 @@ cmake_minimum_required(VERSION 3.5...3.16)
 project(
   nova_context
   VERSION 0.1.0
-  LANGUAGES C)
+  LANGUAGES C ASM)
 
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
@@ -197,6 +197,7 @@ set(ASM_SRC
 
 unset(_asm_suffix)
 
+set_source_files_properties(${ASM_SRC} PROPERTIES LINKER_LANGUAGE C)
 # POWERPC_32/SYSV Special case: https://github.com/boostorg/context/issues/120
 if((NOVA_CONTEXT_ARCHITECTURE STREQUAL ppc32) AND (NOVA_CONTEXT_ABI STREQUAL
                                                    sysv))
@@ -210,8 +211,8 @@ if(NOVA_CONTEXT_ASSEMBLER STREQUAL masm AND NOVA_CONTEXT_ARCHITECTURE STREQUAL
 endif()
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL GNU)
-  set_source_files_properties(${ASM_SRC} PROPERTIES COMPILE_OPTIONS
-                                                    "-x assembler-with-cpp")
+  # set_source_files_properties(${ASM_SRC} PROPERTIES COMPILE_OPTIONS
+  #                                                   "-x assembler-with-cpp")
 endif()
 
 # Boost specific definitions
diff --git a/tile/base/internal/format.h b/tile/base/internal/format.h
index 70027e4..80a5e6d 100644
--- a/tile/base/internal/format.h
+++ b/tile/base/internal/format.h
@@ -57,6 +57,13 @@ auto format_as(const T &val)
   return val.ToString();
 }
 
+template <typename T>
+auto format_as(T *ptr)
+    -> tile::enable_if_t<!std::is_void<tile::remove_cvref_t<T>>::value,
+                         void *> {
+  return reinterpret_cast<void *>(ptr);
+}
+
 #define TILE_INSTANCE_CHRONO_FORMAT_AS(type, suffix)                           \
   inline std::string format_as(const type &val) {                              \
     return tile::detail::format_as_impl(val, suffix);                          \
@@ -80,4 +87,17 @@ TILE_INSTANCE_CHRONO_FORMAT_AS(std::chrono::years, "y")
 #include "fmt/format.h"
 #include "fmt/ostream.h"
 
+inline std::ostream &operator<<(std::ostream &os, std::nullptr_t) {
+  return os << "nullptr";
+}
+
+// template <typename T,
+//           typename = tile::enable_if_t<
+//               !tile::detail::is_streamable<std::ostream, T *>::value &&
+//               !std::is_same<tile::remove_cvref_t<T *>,
+//               std::nullptr_t>::value>>
+// std::ostream &operator<<(std::ostream &os, T *ptr) {
+//   return os << fmt::format("{}", fmt::ptr(ptr));
+// }
+
 #endif // TILE_BASE_INTERNAL_FORMAT_H
diff --git a/tile/fiber/detail/fiber.cc b/tile/fiber/detail/fiber.cc
index 7fa89b2..3aa3a06 100644
--- a/tile/fiber/detail/fiber.cc
+++ b/tile/fiber/detail/fiber.cc
@@ -16,32 +16,38 @@ namespace detail {
 static thread_local Fiber *tls_current_fiber = nullptr;
 static thread_local Fiber *tls_master_fiber = nullptr;
 
-constexpr auto kStackSize = 8192;
-constexpr auto kAlignSize = 16;
+constexpr std::size_t kStackSize = 8192;
+constexpr std::size_t kAlignSize = 16;
 
-void RunProc(void *arg) {
-  auto proc = static_cast<std::function<void()> *>(arg);
-  if (proc) {
-    (*proc)();
+void FiberEntry(fcontext_transfer_t t) {
+  // TILE_LOG_INFO("FiberEntry creater {}, proc {}", t.fctx, t.data);
+  std::function<void()> *fn = static_cast<std::function<void()> *>(t.data);
+  TILE_CHECK_NE(t.data, nullptr);
+  TILE_CHECK_NE(t.fctx, nullptr);
+  try {
+    t = jump_fcontext(t.fctx, nullptr);
+    (*fn)();
+  } catch (const std::exception &e) {
+    // TILE_LOG_ERROR("Exception caught in fiber: {}", e.what());
   }
-  Fiber::MasterFiber()->Resume();
+  TILE_CHECK_NE(t.fctx, nullptr);
+  // TILE_LOG_INFO("FiberEntry End. Resume to {}", t.fctx);
+  jump_fcontext(t.fctx, nullptr);
 }
 
-void RunProc1(fcontext_transfer_t ft) {
-  auto t = jump_fcontext(ft.fctx, nullptr);
+fcontext_t CreateFiber(void *stack, std::size_t stack_size,
+                       std::function<void()> *fn) {
+  void *stack_top = static_cast<char *>(stack) + stack_size;
+  const fcontext_t fctx = make_fcontext(stack_top, stack_size, FiberEntry);
+  TILE_CHECK_NE(fctx, nullptr);
 
-  auto proc = static_cast<std::function<void()> *>(ft.data);
-  TILE_LOG_INFO("proc: {}", fmt::ptr(proc));
-  if (proc) {
-    (*proc)();
-  }
-  Fiber::MasterFiber()->Resume();
+  return jump_fcontext(fctx, fn).fctx;
 }
 
 struct alignas(hardware_destructive_interference_size) Fiber::FiberContext {
   fcontext_t fctx;
-  // tile_ucontext_t uctx;
   std::aligned_storage<kStackSize, kAlignSize>::type stack;
+  std::function<void()> proc;
 };
 
 Fiber *Fiber::Current() noexcept { return tls_current_fiber; }
@@ -56,12 +62,13 @@ std::unique_ptr<Fiber> Fiber::Create(std::function<void()> proc) noexcept {
 }
 
 Fiber::Fiber(std::function<void()> proc)
-    : ctx_(object_pool::Get<FiberContext>().Leak()), proc_(std::move(proc)) {
+    : ctx_(object_pool::Get<FiberContext>().Leak()) {
 
-  // memset(&ctx_->uctx, 0, sizeof(tile_ucontext_t));
-  // memset(&ctx_->stack, 0, kStackSize);
-  if (proc_) {
-    make_fcontext(&ctx_->stack, kStackSize, RunProc1);
+  ctx_->proc = std::move(proc);
+  if (ctx_->proc) {
+    ctx_->fctx = CreateFiber(&ctx_->stack, kStackSize, &ctx_->proc);
+  } else {
+    ctx_->fctx = nullptr;
   }
 }
 
@@ -75,12 +82,14 @@ void Fiber::Resume() {
   auto caller = Current();
   TILE_CHECK_NE(caller, this, "Can't `Resume()` self");
   SetCurrent(this);
-  // tile_ucontext_swap(&caller->ctx_->uctx, &ctx_->uctx);
-  TILE_LOG_INFO("proc: {}", fmt::ptr(&proc_));
-  jump_fcontext(ctx_->fctx, nullptr);
+  // TILE_LOG_INFO("Resume before proc: {}", fmt::ptr(&proc_));
+  ctx_->fctx = jump_fcontext(ctx_->fctx, nullptr).fctx;
+  // TILE_LOG_INFO("Resume after  proc: {}", fmt::ptr(&proc_));
   SetCurrent(caller);
 }
 
+void Fiber::Yield() {}
+
 } // namespace detail
 } // namespace fiber
 
diff --git a/tile/fiber/detail/fiber.h b/tile/fiber/detail/fiber.h
index 6c903f7..8d83756 100644
--- a/tile/fiber/detail/fiber.h
+++ b/tile/fiber/detail/fiber.h
@@ -43,21 +43,20 @@ public:
   Fiber(Fiber &&other) noexcept = default;
   Fiber &operator=(Fiber &&other) noexcept = default;
 
+  // for `Scheduler`
+  void Resume();
+  void Yield();
+
 private:
   TILE_FRIEND_TEST(Fiber, Base);
-  friend void RunProc(void *);
-  friend void RunProc1(struct fcontext_transfer);
   friend Scheduler;
   struct FiberContext;
   friend class ::tile::PoolTraits<FiberContext>;
 
   Fiber(std::function<void()> proc = nullptr);
 
-  void Resume();
-
 private:
   std::unique_ptr<FiberContext> ctx_;
-  std::function<void()> proc_;
   FiberState state_{Ready};
 };
 
diff --git a/tile/fiber/detail/fiber_test.cc b/tile/fiber/detail/fiber_test.cc
index 497b3c1..d431a9e 100644
--- a/tile/fiber/detail/fiber_test.cc
+++ b/tile/fiber/detail/fiber_test.cc
@@ -13,27 +13,19 @@ TEST(Fiber, Base) {
 
   // 0 -> master fiber
   // [1, 9] -> worker fibers
-  std::vector<std::unique_ptr<Fiber>> fibers;
 
-  fibers.emplace_back(Fiber::Create());
-  Fiber::SetMasterFiber(fibers[0].get());
-  Fiber::SetCurrent(fibers[0].get());
-
-  for (int i = 1; i != 10; ++i) {
-    fibers.emplace_back(Fiber::Create([&, i] {
-      while (cnt < kMaxCnt) {
-        ASSERT_EQ(Fiber::Current(), fibers[i].get());
-        ++cnt;
-        Fiber::MasterFiber()->Resume();
-      }
-    }));
-  }
+  auto master_fiber = Fiber::Create();
+  Fiber::SetMasterFiber(master_fiber.get());
+  Fiber::SetCurrent(master_fiber.get());
 
   while (cnt < kMaxCnt) {
-    int old = cnt;
-    auto next_fiber = fibers[Random(1, 9)].get();
+    std::unique_ptr<Fiber> worker_fiber = Fiber::Create([&] {
+      ASSERT_EQ(Fiber::Current(), worker_fiber.get());
+      ++cnt;
+    });
 
-    next_fiber->Resume();
+    int old = cnt;
+    worker_fiber->Resume();
     ++resume_cnt;
     ASSERT_EQ(old + 1, cnt);
     ASSERT_EQ(Fiber::Current(), Fiber::MasterFiber());