i modified an example , but i dont know why it gets locked!

#define BOOST_THREAD_USE_LIB
#include <iostream>
#include <boost/thread.hpp>
#include <vector>
using namespace std;

vector<int> someSharedResource;
boost::mutex mutex;
boost::condition_variable_any condition;
void Writer()
{

    for (int i = 0; i < 10 ; i++)
        {
           boost::unique_lock<boost::mutex> locker(mutex);
           someSharedResource.push_back(i);
          // cout<<boost::this_thread::get_id()<<"\t"<<endl;
           condition.notify_all();
           condition.wait(mutex);
        }

}
void Reader()
{
    int counted_items=0;
   for( int i =0;i<10;i++)
        {
               boost::unique_lock<boost::mutex> locker(mutex);
               condition.wait(mutex);
                cout<<someSharedResource.back()<<"\t"<<boost::this_thread::get_id()<<endl;
                counted_items++;
                condition.notify_all();
        }

}
int main()
{
boost::thread t1(Writer);
boost::thread t2(Reader);
t1.join();
t2.join();
}

is it not that , the mutex is not released until the writer function , gets passed the wait(mutex) method ? and after that waits for the mutex ?
and inside reader function , when it is awakened by the notify_all() method by writer function , it waits until writer releases the mutex and then it owns it and there it executes .
so why do i fell into a locked down of some kind .
if i run this example couple of times , some times it works fine and some times it just hangs at the beginning ( getting locked ? ) whats wrong with it . ?