With multithreaded (parallel execution) or asynchronous programmes, there is a risk of a system entering a blocked state. A deadlock describes such a state in which several processes are waiting for resources that are held by other processes. This creates a cycle of mutual dependencies in which none of the processes involved can progress, as each is dependent on the release of resources by other processes.
For example:
In human terms, it could look like this:
What avoidance/mitigation options are available
- Define a fixed sequence in which resources are requested to avoid cyclical dependencies.
- Use time limits for resource accesses to automatically terminate stalled processes.
- Reduce the need for locking by using lock-free data structures or atomic operations.
- Minimise resource usage and avoid simultaneous requests for multiple resources by the same process.
- Implement mechanisms to react to deadlock situations, e.g. terminating an affected process.
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