Deadlock అంటే ఏమిటి, దాన్ని ఎలా నివారించాలి, తప్పించాలి, లేదా గుర్తించాలి?

1. Mutual exclusion   → a resource is held exclusively (only one holder at a time)
2. Hold and wait      → a thread holds one resource while waiting to acquire another
3. No preemption      → resources can't be forcibly taken; only released voluntarily
4. Circular wait      → a cycle: T1 waits for R2 (held by T2), T2 waits for R1 (held by T1)