1. Race Conditions:
Occurs when two or more threads access shared data and try to change it at the same time, leading to unpredictable results.
How to avoid:
Use synchronization mechanisms like synchronized blocks or Lock objects to ensure only one thread can modify shared data at a time.
java
public synchronized void updateData() {
// Critical section
}
- Deadlocks:
Happens when two or more threads are blocked forever, each waiting for a resource that the other holds.
How to avoid:
- Always acquire locks in a consistent order.
- Use tryLock() instead of lock() to avoid indefinite waiting.
java
if (lock.tryLock()) {
try {
// Critical section
} finally {
lock.unlock();
}
}
- Livelocks:
Threads are not blocked but keep changing their states in response to other threads, leading to no progress.
How to avoid:
Use proper synchronization and ensure that threads can eventually make progress without repeatedly modifying their states based on each other.
- Starvation:
Occurs when a thread is unable to gain regular access to shared resources and is unable to make progress.
How to avoid:
Use fair locks like ReentrantLock with fairness set to true, ensuring that no thread is starved.
java
Lock lock = new ReentrantLock(true); // Fair lock
Key practices to avoid these issues:
1. Minimize synchronized code blocks to reduce performance overhead and potential deadlock.
2. Use thread-safe data structures from java.util.concurrent to avoid manual synchronization in many cases.
By following these approaches, you can mitigate common issues like race conditions, deadlocks, and starvation in multithreaded programming.