Hello dear readers and coders
Welcome to the third ‘Can You Spot the Deadlock?’ trivia. Today’s exercise is still dedicated to the Monitor Pattern. Next one will explore other horizons.
As usual the code is in C#, it does compile but it will not run as is.
So:
- What is the issue here?
- Where does it occur?
- Can you fix it ? if yes how, if not, why
And please share your ideas through the comment!
using System;
using System.Threading;
namespace SpotTheDeadLock
{
internal class SpotTheDeadlock3
{
readonly object _synchro = new object(); // lock object
public int _x = 1; // resulting data
bool _mustStop;
int _iteration = 0;
int []_factor={2,3,5};
// first running thread
public void Runner1(int stepId) {
while (true) {
lock (_synchro) {
if (_iteration % 3 != stepId && !_mustStop)
Monitor.Wait(_synchro);
if (_mustStop)
return;
_x = _x * _factor[stepId];
NextStep();
} // _synchro
} // while
}
private void NextStep() {
if (_iteration == 8)
_mustStop = true;
else
_iteration++;
Monitor.PulseAll(_synchro);
}
public static void Runner() {
SpotTheDeadlock3 agent = new SpotTheDeadlock3();
Thread thread1 = new Thread(() => agent.Runner1(0));
Thread thread2 = new Thread(() => agent.Runner1(1));
Thread thread3 = new Thread(() => agent.Runner1(2));
thread1.Start();
thread2.Start();
thread3.Start();
thread1.Join();
thread2.Join();
thread3.Join();
if (agent._x != 2 * 2 * 2 * 3 * 3 * 3 * 5 * 5 * 5)
throw new ApplicationException("Invalid result");
}
} // class
} // namespace
Quizz time is closed, solution is available here
Many Cores 
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