对于互斥锁:
不要重复锁没锁不要解锁不要赋值/函数间传递/函数返回锁定, 紧接着 defer 解锁
对于读写锁:
读锁 + 读锁 不阻塞其他都阻塞
上代码, 自己品:
package main
import (
"fmt"
"sync"
"time"
)
var i = 0
func count() int {
i++
return i
}
func main() {
var locker sync.Mutex
for i := 0; i < 10; i++ {
go func(i int) {
locker.Lock()
defer locker.Unlock()
fmt.Printf("%d: %dn", i, count())
time.Sleep(time.Millisecond * 200)
}(i)
}
time.Sleep(time.Second * 5)
}
package main
import (
"sync"
)
func main() {
var locker sync.Mutex
locker.Lock()
locker.Lock() // fatal error: all goroutines are asleep - deadlock!
defer locker.Unlock()
}
package main
import (
"sync"
"time"
)
func main() {
var locker sync.Mutex
go func() {
locker.Lock()
locker.Lock() // 阻塞在这里, 没有错误信息, 也没有 panic
defer locker.Unlock()
}()
time.Sleep(time.Second * 5)
}
package main
import (
"fmt"
"sync"
)
func main() {
var locker sync.Mutex
locker.Unlock() // fatal error: sync: unlock of unlocked mutex
fmt.Println("done")
}
package main
import (
"fmt"
"sync"
)
func main() {
var locker sync.Mutex
locker.Lock()
locker.Unlock()
locker.Unlock() // fatal error: sync: unlock of unlocked mutex
fmt.Println("done")
}
package main
import (
"fmt"
"sync"
"time"
)
func main() {
var locker sync.Mutex
go func() {
locker.Unlock() // fatal error: sync: unlock of unlocked mutex
fmt.Println("done")
}()
time.Sleep(time.Second * 2)
}
package main
import (
"fmt"
"sync"
)
func main() {
var locker sync.Mutex
locker2 := locker // lock2 是 locker 的副本, 不一样了
locker.Lock()
locker2.Lock() // 没有阻塞
defer locker2.Unlock()
defer locker.Unlock()
fmt.Println("done")
}
package main
import (
"fmt"
"sync"
"time"
)
func main() {
var locker sync.Mutex
go func() {
locker.Lock()
defer locker.Unlock()
time.Sleep(time.Second * 2)
fmt.Println("aaa")
}()
go func() {
locker.Lock()
defer locker.Unlock()
time.Sleep(time.Second * 2)
fmt.Println("bbb")
}()
time.Sleep(time.Second * 5)
}
package main
import (
"fmt"
"sync"
"time"
)
func main() {
var locker sync.Mutex
locker2 := locker
go func() {
locker.Lock()
defer locker.Unlock()
time.Sleep(time.Second * 2)
fmt.Println("aaa")
}()
go func() {
locker2.Lock()
defer locker2.Unlock()
time.Sleep(time.Second * 2)
fmt.Println("bbb")
}()
time.Sleep(time.Second * 5)
}
package main
import (
"sync"
)
func main() {
var locker sync.RWMutex
locker.Lock()
locker.Lock() // fatal error: all goroutines are asleep - deadlock!
defer locker.Unlock()
defer locker.Unlock()
}
package main
import (
"sync"
)
func main() {
var locker sync.RWMutex
locker.Lock()
locker.RLock() // fatal error: all goroutines are asleep - deadlock!
defer locker.Unlock()
defer locker.RUnlock()
}
package main
import (
"sync"
)
func main() {
var locker sync.RWMutex
locker.RLock()
locker.Lock() // fatal error: all goroutines are asleep - deadlock!
defer locker.RUnlock()
defer locker.Unlock()
}
package main
import (
"fmt"
"sync"
)
func main() {
var locker sync.RWMutex
locker.RLock()
locker.RLock()
defer locker.RUnlock()
defer locker.RUnlock()
fmt.Println("done") // done
}
package main
import (
"fmt"
"sync"
)
func main() {
var locker sync.RWMutex
rlocker := locker.RLocker()
rlocker.Lock()
rlocker.Lock()
defer rlocker.Unlock()
defer rlocker.Unlock()
fmt.Println("done") // done
}
