https://github.com/changsongl/reentrant-lock
reentrant-lock 重入锁
https://github.com/changsongl/reentrant-lock
Last synced: 2 months ago
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reentrant-lock 重入锁
- Host: GitHub
- URL: https://github.com/changsongl/reentrant-lock
- Owner: changsongl
- License: mit
- Created: 2021-12-15T09:59:44.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2021-12-22T02:19:12.000Z (over 3 years ago)
- Last Synced: 2024-12-18T08:39:43.045Z (5 months ago)
- Language: Go
- Size: 5.86 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# reentrant-lock
### 介绍
重入锁，谨慎用于生产环境。此方法通过拿到goroutine id作为锁重入的判断，会因升级go版本而导致不可用。
假如发现此默认获取goroutine id的方法在新的go版本不可以使用，你可以注入自己的获取方法, 通过`SetGidFunc`。
### 示例
````go
func TestNew(t *testing.T) {
m := make(map[string]struct{})
wg := sync.WaitGroup{}
wg.Add(3)
setFunc := func(s string) {
t.Logf("%s entrant", s)
m[s] = struct{}{}
wg.Done()
}
l := Lock{}
go func() {
l.Lock()
setFunc("lock1")
l.Unlock()
l.Lock()
setFunc("lock2")
l.Unlock()
}()
time.Sleep(time.Millisecond)
l.Lock()
setFunc("lock3")
l.Unlock()
wg.Wait()
expected := map[string]struct{}{
"lock1": {},
"lock2": {},
"lock3": {},
}
require.EqualValues(t, expected, m)
}
````
````shell
=== RUN TestNew
lock_test.go:15: lock1 entrant
lock_test.go:15: lock2 entrant
lock_test.go:15: lock3 entrant
--- PASS: TestNew (0.00s)
PASS
````
### 获取goroutine id方式
1. 从stack获得gid, 本包默认使用的。性能会较差10000次>50ms。
````go
package main
import (
"bytes"
"fmt"
"runtime"
"strconv"
)
func main() {
fmt.Println(GetGID())
}
func GetGID() uint64 {
b := make([]byte, 64)
b = b[:runtime.Stack(b, false)]
b = bytes.TrimPrefix(b, []byte("goroutine "))
b = b[:bytes.IndexByte(b, ' ')]
n, _ := strconv.ParseUint(string(b), 10, 64)
return n
}
````
2. 修改go的代码 `src/runtime/runtime2.go`, 但以后只能在自己的go代码编译。
````go
func Goid() int64 {
_g_ := getg()
return _g_.goid
}
````
3. CGo去获得gid, 不影响移植和性能。但要开启cgo.
````cgo
// 文件id.c:
#include "runtime.h"
int64 ·Id(void) {
return g->goid;
}
````
````go
// 文件id.go
package id
func Id() int64
````
4. 通过汇编获取gid。那就是通过汇编获取goroutine id的方法。原理是：通过getg方法（汇编实现）获取到当前goroutine的g结构地址，根据偏移量计算出成员goid int的地址，然后取出该值即可。