diff --git a/ants_benchmark_test.go b/ants_benchmark_test.go
index 56d94f7..de1f320 100644
--- a/ants_benchmark_test.go
+++ b/ants_benchmark_test.go
@@ -89,6 +89,7 @@ func BenchmarkAntsPoolWithFunc(b *testing.B) {
 	})
 	defer p.Release()
 
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		for j := 0; j < RunTimes; j++ {
 			wg.Add(1)
diff --git a/pool.go b/pool.go
index 96873cd..8f0abba 100644
--- a/pool.go
+++ b/pool.go
@@ -23,7 +23,6 @@
 package ants
 
 import (
-	"math"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -45,10 +44,6 @@ type Pool struct {
 	// expiryDuration set the expired time (second) of every worker.
 	expiryDuration time.Duration
 
-	// freeSignal is used to notice pool there are available
-	// workers which can be sent to work.
-	freeSignal chan sig
-
 	// workers is a slice that store the available workers.
 	workers []*Worker
 
@@ -77,7 +72,6 @@ func (p *Pool) periodicallyPurge() {
 				break
 			}
 			n = i
-			<-p.freeSignal
 			w.task <- nil
 			idleWorkers[i] = nil
 		}
@@ -104,7 +98,6 @@ func NewTimingPool(size, expiry int) (*Pool, error) {
 	}
 	p := &Pool{
 		capacity:       int32(size),
-		freeSignal:     make(chan sig, math.MaxInt32),
 		release:        make(chan sig, 1),
 		expiryDuration: time.Duration(expiry) * time.Second,
 	}
@@ -119,8 +112,7 @@ func (p *Pool) Submit(task f) error {
 	if len(p.release) > 0 {
 		return ErrPoolClosed
 	}
-	w := p.getWorker()
-	w.task <- task
+	p.getWorker().task <- task
 	return nil
 }
 
@@ -160,7 +152,6 @@ func (p *Pool) Release() error {
 		p.lock.Lock()
 		idleWorkers := p.workers
 		for i, w := range idleWorkers {
-			<-p.freeSignal
 			w.task <- nil
 			idleWorkers[i] = nil
 		}
@@ -172,13 +163,13 @@ func (p *Pool) Release() error {
 
 //-------------------------------------------------------------------------
 
-// incrRunning increases the number of the currently running goroutines
-func (p *Pool) incrRunning() {
+// incRunning increases the number of the currently running goroutines
+func (p *Pool) incRunning() {
 	atomic.AddInt32(&p.running, 1)
 }
 
-// decrRunning decreases the number of the currently running goroutines
-func (p *Pool) decrRunning() {
+// decRunning decreases the number of the currently running goroutines
+func (p *Pool) decRunning() {
 	atomic.AddInt32(&p.running, -1)
 }
 
@@ -193,7 +184,6 @@ func (p *Pool) getWorker() *Worker {
 	if n < 0 {
 		waiting = p.Running() >= p.Cap()
 	} else {
-		<-p.freeSignal
 		w = idleWorkers[n]
 		idleWorkers[n] = nil
 		p.workers = idleWorkers[:n]
@@ -201,21 +191,27 @@ func (p *Pool) getWorker() *Worker {
 	p.lock.Unlock()
 
 	if waiting {
-		<-p.freeSignal
-		p.lock.Lock()
-		idleWorkers = p.workers
-		l := len(idleWorkers) - 1
-		w = idleWorkers[l]
-		idleWorkers[l] = nil
-		p.workers = idleWorkers[:l]
-		p.lock.Unlock()
+		for {
+			p.lock.Lock()
+			idleWorkers = p.workers
+			l := len(idleWorkers) - 1
+			if l < 0 {
+				p.lock.Unlock()
+				continue
+			}
+			w = idleWorkers[l]
+			idleWorkers[l] = nil
+			p.workers = idleWorkers[:l]
+			p.lock.Unlock()
+			break
+		}
 	} else if w == nil {
 		w = &Worker{
 			pool: p,
 			task: make(chan f, 1),
 		}
 		w.run()
-		p.incrRunning()
+		p.incRunning()
 	}
 	return w
 }
@@ -226,5 +222,4 @@ func (p *Pool) putWorker(worker *Worker) {
 	p.lock.Lock()
 	p.workers = append(p.workers, worker)
 	p.lock.Unlock()
-	p.freeSignal <- sig{}
 }
diff --git a/pool_func.go b/pool_func.go
index ee8c9c5..890e7be 100644
--- a/pool_func.go
+++ b/pool_func.go
@@ -23,7 +23,6 @@
 package ants
 
 import (
-	"math"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -43,10 +42,6 @@ type PoolWithFunc struct {
 	// expiryDuration set the expired time (second) of every worker.
 	expiryDuration time.Duration
 
-	// freeSignal is used to notice pool there are available
-	// workers which can be sent to work.
-	freeSignal chan sig
-
 	// workers is a slice that store the available workers.
 	workers []*WorkerWithFunc
 
@@ -78,7 +73,6 @@ func (p *PoolWithFunc) periodicallyPurge() {
 				break
 			}
 			n = i
-			<-p.freeSignal
 			w.args <- nil
 			idleWorkers[i] = nil
 		}
@@ -105,7 +99,6 @@ func NewTimingPoolWithFunc(size, expiry int, f pf) (*PoolWithFunc, error) {
 	}
 	p := &PoolWithFunc{
 		capacity:       int32(size),
-		freeSignal:     make(chan sig, math.MaxInt32),
 		release:        make(chan sig, 1),
 		expiryDuration: time.Duration(expiry) * time.Second,
 		poolFunc:       f,
@@ -124,8 +117,7 @@ func (p *PoolWithFunc) Serve(args interface{}) error {
 	if len(p.release) > 0 {
 		return ErrPoolClosed
 	}
-	w := p.getWorker()
-	w.args <- args
+	p.getWorker().args <- args
 	return nil
 }
 
@@ -165,7 +157,6 @@ func (p *PoolWithFunc) Release() error {
 		p.lock.Lock()
 		idleWorkers := p.workers
 		for i, w := range idleWorkers {
-			<-p.freeSignal
 			w.args <- nil
 			idleWorkers[i] = nil
 		}
@@ -177,13 +168,13 @@ func (p *PoolWithFunc) Release() error {
 
 //-------------------------------------------------------------------------
 
-// incrRunning increases the number of the currently running goroutines
-func (p *PoolWithFunc) incrRunning() {
+// incRunning increases the number of the currently running goroutines
+func (p *PoolWithFunc) incRunning() {
 	atomic.AddInt32(&p.running, 1)
 }
 
-// decrRunning decreases the number of the currently running goroutines
-func (p *PoolWithFunc) decrRunning() {
+// decRunning decreases the number of the currently running goroutines
+func (p *PoolWithFunc) decRunning() {
 	atomic.AddInt32(&p.running, -1)
 }
 
@@ -198,7 +189,6 @@ func (p *PoolWithFunc) getWorker() *WorkerWithFunc {
 	if n < 0 {
 		waiting = p.Running() >= p.Cap()
 	} else {
-		<-p.freeSignal
 		w = idleWorkers[n]
 		idleWorkers[n] = nil
 		p.workers = idleWorkers[:n]
@@ -206,21 +196,27 @@ func (p *PoolWithFunc) getWorker() *WorkerWithFunc {
 	p.lock.Unlock()
 
 	if waiting {
-		<-p.freeSignal
-		p.lock.Lock()
-		idleWorkers = p.workers
-		l := len(idleWorkers) - 1
-		w = idleWorkers[l]
-		idleWorkers[l] = nil
-		p.workers = idleWorkers[:l]
-		p.lock.Unlock()
+		for {
+			p.lock.Lock()
+			idleWorkers = p.workers
+			l := len(idleWorkers) - 1
+			if l < 0 {
+				p.lock.Unlock()
+				continue
+			}
+			w = idleWorkers[l]
+			idleWorkers[l] = nil
+			p.workers = idleWorkers[:l]
+			p.lock.Unlock()
+			break
+		}
 	} else if w == nil {
 		w = &WorkerWithFunc{
 			pool: p,
 			args: make(chan interface{}, 1),
 		}
 		w.run()
-		p.incrRunning()
+		p.incRunning()
 	}
 	return w
 }
@@ -231,5 +227,4 @@ func (p *PoolWithFunc) putWorker(worker *WorkerWithFunc) {
 	p.lock.Lock()
 	p.workers = append(p.workers, worker)
 	p.lock.Unlock()
-	p.freeSignal <- sig{}
 }
diff --git a/worker.go b/worker.go
index aa4e761..a0c2faf 100644
--- a/worker.go
+++ b/worker.go
@@ -46,7 +46,7 @@ func (w *Worker) run() {
 	go func() {
 		for f := range w.task {
 			if f == nil {
-				w.pool.decrRunning()
+				w.pool.decRunning()
 				return
 			}
 			f()
diff --git a/worker_func.go b/worker_func.go
index 277ee31..a02264b 100644
--- a/worker_func.go
+++ b/worker_func.go
@@ -46,7 +46,7 @@ func (w *WorkerWithFunc) run() {
 	go func() {
 		for args := range w.args {
 			if args == nil {
-				w.pool.decrRunning()
+				w.pool.decRunning()
 				return
 			}
 			w.pool.poolFunc(args)