import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.sync.Mutex
import kotlinx.coroutines.sync.withLock

fun main() {
    val t = TestClass()
    runBlocking { t.m1() }
    println("end")
}

class TestClass {
    private val mutex = Mutex()

    suspend fun m1() = mutex.withLock(this) {
        println("m1")
        m2()
    }

    suspend fun m2() = mutex.withLock(this) {
        println("m2")
    }
}