Threads And Concurrency Questions Medium
A deadlock in thread synchronization refers to a situation where two or more threads are unable to proceed because each thread is waiting for a resource that is held by another thread in the same group. In other words, it is a state where two or more threads are stuck in a circular dependency, causing them to be unable to make progress.
Deadlocks typically occur when multiple threads compete for shared resources and each thread holds a resource while waiting for another resource to be released. This can happen due to improper synchronization or resource allocation strategies.
There are four necessary conditions for a deadlock to occur, known as the Coffman conditions:
1. Mutual Exclusion: At least one resource must be held in a non-sharable mode, meaning only one thread can access it at a time.
2. Hold and Wait: A thread must be holding at least one resource and waiting to acquire additional resources held by other threads.
3. No Preemption: Resources cannot be forcibly taken away from a thread; they can only be released voluntarily.
4. Circular Wait: There must be a circular chain of two or more threads, where each thread is waiting for a resource held by another thread in the chain.
To prevent deadlocks, various techniques can be employed, such as resource allocation strategies like the Banker's algorithm, using timeouts or deadlock detection algorithms, and ensuring proper synchronization and resource management practices.