Woodstock Blog

a tech blog for general algorithmic interview questions

[Design] Multithreading - Deadlock Prevention


How to prevent deadlock? (question from MIT handouts 1)


Preventing one of the 4 conditions will prevent deadlock:

  1. Removing the mutual exclusion condition, but not very possible.

  2. The hold and wait conditions may be removed by requiring processes to request all the resources they will need before starting up.

  3. The no preemption condition may also be difficult or impossible to avoid as a process has to be able to have a resource for a certain amount of time, or the processing outcome may be inconsistent or thrashing may occur.

  4. The final condition is the circular wait condition. Approaches that avoid circular waits include disabling interrupts during critical sections and using a hierarchy to determine a partial ordering of resources.


Assign an order to our locks (require that the locks always acquired in order).

This prevent 2 thread waiting to get the resource in each other’s hand.