From 75dcc566b3c5dbf83f623b6e1b8cf1490106a97e Mon Sep 17 00:00:00 2001
From: John <john@johng.cn>
Date: Mon, 3 Jun 2019 09:09:40 +0800
Subject: [PATCH] improve grpool to ensure atomicity for function Add

---
 g/os/grpool/grpool.go    | 14 ++++++++++----
 geg/os/grpool/grpool5.go | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)
 create mode 100644 geg/os/grpool/grpool5.go

diff --git a/g/os/grpool/grpool.go b/g/os/grpool/grpool.go
index 1de07ea32..8d2bf116c 100644
--- a/g/os/grpool/grpool.go
+++ b/g/os/grpool/grpool.go
@@ -59,10 +59,17 @@ func Jobs() int {
 // The job will be executed asynchronously.
 func (p *Pool) Add(f func()) {
     p.list.PushFront(f)
-    // checking whether to create a new goroutine or not.
-    if p.count.Val() != p.limit {
-        p.fork()
+    // check whether to create a new goroutine or not.
+    if p.count.Val() == p.limit {
+		return
     }
+	// ensure atomicity.
+	if p.limit != -1 && p.count.Add(1) > p.limit {
+		p.count.Add(-1)
+		return
+	}
+    // fork a new goroutine to consume the job list.
+	p.fork()
 }
 
 // Size returns current goroutine count of the pool.
@@ -77,7 +84,6 @@ func (p *Pool) Jobs() int {
 
 // fork creates a new goroutine pool.
 func (p *Pool) fork() {
-	p.count.Add(1)
     go func() {
     	defer p.count.Add(-1)
     	job := (interface{})(nil)
diff --git a/geg/os/grpool/grpool5.go b/geg/os/grpool/grpool5.go
new file mode 100644
index 000000000..3d12ee5db
--- /dev/null
+++ b/geg/os/grpool/grpool5.go
@@ -0,0 +1,19 @@
+package main
+
+import (
+	"fmt"
+	"github.com/gogf/gf/g/os/grpool"
+	"time"
+)
+
+func main() {
+	p := grpool.New(1)
+	for i := 0; i < 10; i++ {
+		v := i
+		p.Add(func() {
+			fmt.Println(v)
+			time.Sleep(3*time.Second)
+		})
+	}
+	time.Sleep(time.Minute)
+}