#118 fix read lock netst

[orientlu]

fix read lock nest

[orientlu]

is a bug, i test lorasever project ,found my gateway-bridge will block on handlePackage where try to get the read lock. and i think the block is cause by read lock nest
1.function handlePushData is called by handlePacket which will get the read lock,
2.fucntion handleStats is called by handlePushData and will get the read lock too
here, if somewhere get the write lock betwen 1 and 2, will cause deadlock

[brocaar]

I don't believe this should create a deadlock, as there can be multiple read-locks simultaneously (in contrast to a acquiring a write-lock, which will wait until all other read or write locks are released).

However you're right that there is no need to get a new read-lock in the handleStats function.

[orientlu]

I don't believe this should create a deadlock, as there can be multiple read-locks simultaneously (in contrast to a acquiring a write-lock, which will wait until all other read or write locks are released).

However you're right that there is no need to get a new read-lock in the handleStats function.

yes, i totally agree multiple read-locks and acquiring a write-lock which will wait until all other locks are released.
but what i mean is this scene：　get multiple read-locks in the sam function call.
the example show what i mean

package main
import "fmt"
import "sync"
import "time"

var testMutex sync.RWMutex

func main() {
	fmt.Println("start")

	go func() {
		testMutex.RLock()
		defer testMutex.RUnlock()
		fmt.Println("get r lock 1")
		time.Sleep(time.Duration(3) * time.Second) // wait write lock

		fmt.Println("try to get r lock 2")
		// block by write lock
                testMutex.RLock()
		fmt.Println("get r lock 2")
		defer testMutex.RUnlock()
	}()

	go func() {
		time.Sleep(time.Duration(1) * time.Second) 
                // get write lock after one read lock had got
		// block by read lock 1
                fmt.Println("try to get w lock")
		testMutex.Lock()
		defer testMutex.Unlock()
		fmt.Println("get w lock")
	}()

	time.Sleep(time.Duration(20) * time.Second)
	fmt.Println("killed")
}

[brocaar]

Sorry, you're right. When it tries to acquire a write-lock between two read-locks then there is indeed a deadlock. Good catch 👍