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There are also potentially problematic conditions that you need to be aware of when designing or implementing multi-threaded applications. These conditions are known as starvation and livelock: StarvationStarvation describes a situation where a thread is unable to gain regular access to shared resources and is unable to make progress. This happens when shared resources are made unavailable for long periods by "greedy" threads.For example, suppose an object provides a synchronized method that often takes a long time to return. If one thread invokes this method frequently, other threads that also need frequent synchronized access to the same object will often be blocked. LivelockA thread often acts in response to the action of another thread. If the other thread's action is also a response to the action of another thread, then livelock may result. As with deadlock, livelocked threads are unable to make further progress. However, the threads are not blocked — they are simply too busy responding to each other to resume work.This is analogous to two people attempting to pass each other in a corridor: Larry moves to his left to let Curly pass, while Curly moves to his right to let Larry pass. Seeing that they are still blocking each other, Larry moves to his right, while Curly moves to his left. They're still blocking each other, so... |
| The page was last updated February 19, 2008 |