diff --git a/x/io/_demo/asyncdemo/async.go b/x/io/_demo/asyncdemo/async.go
index 2fdbfa85..ff75e943 100644
--- a/x/io/_demo/asyncdemo/async.go
+++ b/x/io/_demo/asyncdemo/async.go
@@ -169,10 +169,11 @@ func GetUserCompiled(name string) *io.PromiseImpl[User] {
 				state2.Exec = P.Exec
 				state2.Parent = P
 				state2.Call()
-				log.Printf("TextCompiled state2: %v\n", state2)
+				log.Printf("TextCompiled state2: %+v\n", state2)
 				return
 			case 2:
 				P.Next = -1
+				log.Printf("TextCompiled state2: %+v\n", state2)
 				body, err := state2.Value, state2.Err
 				if err != nil {
 					resolve(User{}, err)
@@ -380,10 +381,10 @@ func DemoCompiled() *io.PromiseImpl[io.Void] {
 			case 1:
 				P.Next = 2
 				user, err := state1.Value, state1.Err
-				log.Printf("user: %v, err: %v\n", user, err)
+				log.Printf("user: %+v, err: %v\n", user, err)
 
 				state2 = io.Race[User](GetUserCompiled("2"), GetUserCompiled("3"), GetUserCompiled("4"))
-				log.Printf("state2: %v\n", state2)
+				log.Printf("state2: %+v\n", state2)
 				state2.Exec = P.Exec
 				state2.Parent = P
 				state2.Call()
@@ -393,10 +394,10 @@ func DemoCompiled() *io.PromiseImpl[io.Void] {
 
 				P.Next = 3
 				user, err := state2.Value, state2.Err
-				log.Printf("race user: %v, err: %v\n", user, err)
+				log.Printf("race user: %+v, err: %v\n", user, err)
 
 				state3 = io.All[User]([]io.AsyncCall[User]{GetUserCompiled("5"), GetUserCompiled("6"), GetUserCompiled("7")})
-				log.Printf("state3: %v\n", state3)
+				log.Printf("state3: %+v\n", state3)
 				state3.Exec = P.Exec
 				state3.Parent = P
 				state3.Call()
@@ -408,7 +409,7 @@ func DemoCompiled() *io.PromiseImpl[io.Void] {
 				log.Println(users, err)
 
 				state4 = io.Await3Compiled[User, float64, io.Void](GetUserCompiled("8"), GetScoreCompiled(), DoUpdateCompiled("update sth."))
-				log.Printf("state4: %v\n", state4)
+				log.Printf("state4: %+v\n", state4)
 				state4.Exec = P.Exec
 				state4.Parent = P
 				state4.Call()
diff --git a/x/io/extra.go b/x/io/extra.go
index cd09f66a..163b20e6 100644
--- a/x/io/extra.go
+++ b/x/io/extra.go
@@ -52,59 +52,98 @@ type Result[T any] struct {
 
 // llgo:link Race llgo.race
 func Race[OutT any](acs ...AsyncCall[OutT]) *PromiseImpl[OutT] {
+	if len(acs) == 0 {
+		panic("face: no promise")
+	}
+	ps := make([]*PromiseImpl[OutT], len(acs))
+	for idx, ac := range acs {
+		ps[idx] = ac.(*PromiseImpl[OutT])
+	}
+	remaining := len(acs)
+	returned := false
 	P := &PromiseImpl[OutT]{}
 	P.Debug = "Race"
 	P.Func = func(resolve func(OutT, error)) {
-		P.Next = -1
-		rc := make(chan Result[OutT], len(acs))
-		for _, ac := range acs {
-			ac := ac
-			go func(ac AsyncCall[OutT]) {
-				v, err := Run[OutT](ac)
-				rc <- Result[OutT]{v, err}
-			}(ac)
-		}
-
-		v := <-rc
-		if debugAsync {
-			log.Printf("io.Race done: %+v won the race\n", v)
-		}
-		resolve(v.V, v.Err)
-		go func() {
-			count := 1
-			for count < len(acs) {
-				<-rc
-				count++
+		switch P.Next {
+		case 0:
+			P.Next = 1
+			for _, p := range ps {
+				p.Exec = P.Exec
+				p.Parent = P
+				p.Call()
 			}
-			close(rc)
-		}()
+			return
+		case 1:
+			remaining--
+			if remaining < 0 {
+				log.Fatalf("race: remaining < 0: %+v\n", remaining)
+			}
+			if returned {
+				return
+			}
+
+			for _, p := range ps {
+				if p.Done() {
+					if debugAsync {
+						log.Printf("io.Race done: %+v won the race\n", p)
+					}
+					returned = true
+					resolve(p.Value, p.Err)
+					return
+				}
+			}
+			log.Fatalf("no promise done: %+v\n", ps)
+			return
+		default:
+			panic("unreachable")
+		}
 	}
 	return P
 }
 
 func All[OutT any](acs []AsyncCall[OutT]) *PromiseImpl[[]Result[OutT]] {
+	ps := make([]*PromiseImpl[OutT], len(acs))
+	for idx, ac := range acs {
+		ps[idx] = ac.(*PromiseImpl[OutT])
+	}
+	done := 0
 	P := &PromiseImpl[[]Result[OutT]]{}
 	P.Debug = "All"
 	P.Func = func(resolve func([]Result[OutT], error)) {
-		P.Next = -1
-		wg := sync.WaitGroup{}
-		ret := make([]Result[OutT], len(acs))
-		for idx, ac := range acs {
-			idx := idx
-			ac := ac
-			wg.Add(1)
-			go func(ac AsyncCall[OutT]) {
-				v, err := Run[OutT](ac)
-				ret[idx] = Result[OutT]{v, err}
-				wg.Done()
-			}(ac)
-		}
+		switch P.Next {
+		case 0:
+			P.Next = 1
+			for _, p := range ps {
+				p.Exec = P.Exec
+				p.Parent = P
+				p.Call()
+			}
+			return
+		case 1:
+			done++
+			if done < len(acs) {
+				return
+			}
+			P.Next = -1
 
-		wg.Wait()
-		if debugAsync {
-			log.Printf("io.All done: %+v\n", ret)
+			for _, p := range ps {
+				if !p.Done() {
+					log.Fatalf("io.All: not done: %+v\n", p)
+				}
+			}
+
+			ret := make([]Result[OutT], len(acs))
+			for idx, p := range ps {
+				ret[idx] = Result[OutT]{p.Value, p.Err}
+			}
+			if debugAsync {
+				log.Printf("io.All done: %+v\n", ret)
+			}
+			resolve(ret, nil)
+			return
+		default:
+			panic("unreachable")
 		}
-		resolve(ret, nil)
 	}
 	return P
 }
@@ -142,35 +181,116 @@ type Await3Result[T1 any, T2 any, T3 any] struct {
 	Err error
 }
 
-// TODO(lijie): rewrite to unblock and avoid goroutine
 func Await3Compiled[OutT1, OutT2, OutT3 any](
 	ac1 AsyncCall[OutT1], ac2 AsyncCall[OutT2], ac3 AsyncCall[OutT3],
 	timeout ...time.Duration) *PromiseImpl[Await3Result[OutT1, OutT2, OutT3]] {
+	p1 := ac1.(*PromiseImpl[OutT1])
+	p2 := ac2.(*PromiseImpl[OutT2])
+	p3 := ac3.(*PromiseImpl[OutT3])
+	remaining := 3
 	P := &PromiseImpl[Await3Result[OutT1, OutT2, OutT3]]{}
 	P.Debug = "Await3"
 	P.Func = func(resolve func(Await3Result[OutT1, OutT2, OutT3], error)) {
-		P.Next = -1
+		switch P.Next {
+		case 0:
+			P.Next = 1
+			p1.Exec = P.Exec
+			p1.Parent = P
+			p1.Call()
 
-		ret := Await3Result[OutT1, OutT2, OutT3]{}
-		wg := sync.WaitGroup{}
-		wg.Add(3)
+			p2.Exec = P.Exec
+			p2.Parent = P
+			p2.Call()
 
-		go func() {
-			defer wg.Done()
-			ret.V1, ret.Err = Run[OutT1](ac1)
-		}()
-		go func() {
-			defer wg.Done()
-			ret.V2, ret.Err = Run[OutT2](ac2)
-		}()
-		go func() {
-			defer wg.Done()
-			ret.V3, ret.Err = Run[OutT3](ac3)
-		}()
-		wg.Wait()
-		if debugAsync {
-			log.Printf("Await3 done: %+v\n", ret)
+			p3.Exec = P.Exec
+			p3.Parent = P
+			p3.Call()
+			return
+		case 1:
+			remaining--
+			if remaining > 0 {
+				return
+			}
+			P.Next = -1
+			// TODO(lijie): return every error?
+			if !p1.Done() || !p2.Done() || !p3.Done() {
+				log.Fatalf("io.Await3: not done: %+v, %+v, %+v\n", p1, p2, p3)
+			}
+
+			var err error
+			if p1.Err != nil {
+				err = p1.Err
+			} else if p2.Err != nil {
+				err = p2.Err
+			} else if p3.Err != nil {
+				err = p3.Err
+			}
+
+			resolve(Await3Result[OutT1, OutT2, OutT3]{
+				V1: p1.Value, V2: p2.Value, V3: p3.Value,
+				Err: err,
+			}, err)
+			return
+		default:
+			panic("unreachable")
 		}
+	}
+	return P
+}
+
+// / PAll is a parallel version of All.
+func PAll[OutT any](acs ...AsyncCall[OutT]) (resolve Promise[[]Result[OutT]]) {
+	panic("todo: PAll")
+}
+
+func PAllCompiled[OutT any](acs ...AsyncCall[OutT]) *PromiseImpl[[]Result[OutT]] {
+	P := &PromiseImpl[[]Result[OutT]]{}
+	P.Debug = "Parallel"
+	P.Func = func(resolve func([]Result[OutT], error)) {
+		ret := make([]Result[OutT], len(acs))
+		wg := sync.WaitGroup{}
+		for idx, ac := range acs {
+			idx := idx
+			ac := ac
+			wg.Add(1)
+			go func(ac AsyncCall[OutT]) {
+				v, err := Run[OutT](ac)
+				ret[idx] = Result[OutT]{v, err}
+				wg.Done()
+			}(ac)
+		}
+		wg.Wait()
+		resolve(ret, nil)
+	}
+	return P
+}
+
+// / PAwait3 is a parallel version of Await3.
+func PAwait3[OutT1, OutT2, OutT3 any](ac1 AsyncCall[OutT1], ac2 AsyncCall[OutT2], ac3 AsyncCall[OutT3]) (resolve Promise[Await3Result[OutT1, OutT2, OutT3]]) {
+	panic("todo: PAwait2")
+}
+
+func PAwait3Compiled[OutT1, OutT2, OutT3 any](
+	ac1 AsyncCall[OutT1], ac2 AsyncCall[OutT2], ac3 AsyncCall[OutT3]) *PromiseImpl[Await3Result[OutT1, OutT2, OutT3]] {
+	P := &PromiseImpl[Await3Result[OutT1, OutT2, OutT3]]{}
+	P.Debug = "Parallel3"
+	P.Func = func(resolve func(Await3Result[OutT1, OutT2, OutT3], error)) {
+		ret := Await3Result[OutT1, OutT2, OutT3]{}
+		wg := sync.WaitGroup{}
+		wg.Add(3)
+		go func() {
+			ret.V1, ret.Err = Run[OutT1](ac1)
+			wg.Done()
+		}()
+		go func() {
+			ret.V2, ret.Err = Run[OutT2](ac2)
+			wg.Done()
+		}()
+		go func() {
+			ret.V3, ret.Err = Run[OutT3](ac3)
+			wg.Done()
+		}()
+		wg.Wait()
 		resolve(ret, nil)
 	}
 	return P