Separating std::threads by condtions

Program to invoke threads on the priority basis

I am trying to run threads as priority 1 and other priority threads(except 1),

In here thread t2 is of priority 2 the 3 threads t1,t2, and t3 are in wait . and thread t4 goes and calls signals with priority 2. //- I want it to invoke only threads with priority other than 1

I am trying to run threads as priority 1 and other priority threads(except 1),

In here thread t2 is of priority 2 the 3 threads t1,t2, and t3 are in wait . and thread t4 goes and calls signals with priority 2. //- I want it to invoke only threads with priority other than 1

The output of this program is

single notifyall cv.wait(master); cv1.wait(master); cv.wait(master);```

Looking for the explanation of the output

#include <condition_variable>
#include <thread>
#include <chrono>
using namespace std;
std::condition_variable cv;
std::condition_variable cv1;
std::mutex cv_m; 

void waits(int priority)
{
    std::unique_lock<std::mutex> master(cv_m);
    
        if(priority == 1){
            std::cout<<"cv.wait(master);"<<std::endl;
            cv.wait(master);   
        }
        else {
            std::cout<<"cv1.wait(master);"<<std::endl;
         cv1.wait(master);   
        }
std::cout<<"Priority"<<priority<<std::endl;
}
 
void signals(int priority)
{
    switch (priority){
            case 1:
                std::cout<<"both notifyall"<<std::endl;
                cv.notify_all();
                cv1.notify_all(); 
                break;

            case 2:
                std::cout<<"single notifyall"<<std::endl;
                cv1.notify_all();
                break;
        }
}
 
int main()
{
    std::thread t1(waits,1), t2(waits,2), t3(waits,1),
 t4(signals,1);
    t1.join(); 
    t2.join(); 
    t3.join();
    t4.join();

}

I am trying to run threads as priority 1 and other priority threads(except 1), 


In here thread t2 is of priority 2  the 3 threads t1,t2, and t3 are in wait . and thread t4 goes and calls signals with priority 2. //- **I want it to invoke only threads with priority other than 1**

**The output of this program is** 

single notifyall
cv.wait(master);
cv1.wait(master);
cv.wait(master);```

but the priority 1 threads were never signaled.

**Probable explanation from my side:**

The reason is the condition on which condition variables are waiting. 
Here they are waiting on Locks, with no other condition and once the Thread 4 - Signals, it says that the master lock is available, and it becomes available for both priority 1 and other priority threads, so any thread waiting on the lock picks it.

Looking for better ideas....................... and Reasons if Any