How to avoid deadlock in .NET

Question

Is there are any common practices or rules to avoid deadlock in a program? Also is there any support from CLR or any instrument from language/framework to Handle such scenario?

Answer 1

Note that little of this is .net-specific:

The biggest way of avoiding a deadlock is to lock in a consistent order; this means you get regular blocking rather than a deadlock, but requires much thought and planning about what you are locking and when. Of course, this thought and planning is necessary anyway.

One simple way of achieving this is: try to only need one lock object at a time; so instead of locking A and B, you lock (separately) A then B. This too requires thought and planning, but is usually achievable.

Taking it more generally, avoiding over-granular locks can be a huge sanity-saver here. For lock objects that could compete, put serious consideration into just using a single lock of for both concepts. In many cases this doesn't hugely impact the time spent competing, but makes the code much simpler and more reliable.

Actually, one gripe I do have with the language is that "take a lock but with a timeout" is so much more code-intensive than "take a lock". Ensuring you always have timeouts can also ensure that a total lockup becomes recoverable. But this should mainly just be used to identify areas that are locking in the wrong order, so that you can fix them.