// bm.cpp

//  g++ test.cpp -lboost_thread-mt && ./a.out

// the ration of XXX and YYY determines 
// if this works or deadlocks
int XXX = 20;
int YYY = 10;

#include <boost/thread.hpp>
#include <boost/thread/shared_mutex.hpp>

#include <unistd.h>
#include <iostream>

using namespace std;



void sleepmillis( useconds_t miliis ) {
    usleep( miliis * 1000 );
}

void worker1( boost::shared_mutex * lk , int * x ) {
    (*x)++; // 1
    cout << "lock b try" << endl;
    while ( 1 ) {
        if ( lk->timed_lock( boost::posix_time::milliseconds( XXX ) ) )
            break;
        sleepmillis(YYY);
    }
    cout << "lock b got" << endl;
    (*x)++; // 2
    lk->unlock();
}

void worker2( boost::shared_mutex * lk , int * x ) {
    cout << "lock c try" << endl;
    lk->lock_shared();
    (*x)++;
    cout << "lock c got" << endl;
    lk->unlock_shared();
    cout << "lock c unlocked" << endl;
    (*x)++;
}

int main() { 
    
    // create
    boost::shared_mutex* lk = new boost::shared_mutex();
    
    // read lock
    cout << "lock a" << endl;
    lk->lock_shared();
    
    int x1 = 0;
    boost::thread t1( boost::bind( worker1 , lk , &x1 ) );
    while ( ! x1 );
    assert( x1 == 1 );
    sleepmillis( 500 );
    assert( x1 == 1 );
    
    int x2 = 0;
    boost::thread t2( boost::bind( worker2, lk , &x2 ) );
    t2.join();
    assert( x2 == 2 );
    
    lk->unlock_shared();
    cout << "unlock a" << endl;
    
    for ( int i=0; i<2000; i++ ) {
        if ( x1 == 2 )
            break;
        sleepmillis(10);
    }
    
    assert( x1 == 2 );
    t1.join();
    delete lk;
}