exclusive-access-wrong.swift

import Foundation

struct Node {
    var childs: [String] = []
    
    var lock = NSRecursiveLock()
    
    init() {}
    
    mutating func clearChilds() {
        if childs.isEmpty {
            lock.lock()
            childs.removeAll()
            lock.unlock()
        }
    }
}

var node = Node()
DispatchQueue(label: "queue.test.exclusive-access").async {
    node.clearChilds()
}

DispatchQueue(label: "queue.test.exclusive-access.other").async {
    node.clearChilds()
}