The Deadlock Dilemma
Ever seen your payment processor come to a screeching halt? When two threads try to swap funds between accounts A and B simultaneously, each one may grab one mutex and then wait forever for the other. Congratulations—you’ve invented the classic circular wait deadlock.
## The Power of Ordered Locking
### Consistent Global Order
The cure is embarrassingly simple: always acquire your locks in the same sequence. Sort accounts by ID and lock the smaller one first. Now no two threads can hold conflicting locks because they all follow the golden rule.
### Atomic Multi-Lock Primitives
Languages like C++ give you std::lock()
or std::scoped_lock
to grab multiple mutexes at once. If they can’t all be acquired, they back off and retry—saving you from manual backoff loops and that 2am PagerDuty page.
## Common Pitfalls to Avoid
– “Just shrink critical sections.” Tiny scopes still risk intermediate inconsistent states.
- “One giant global lock.” Sure, if you don’t value throughput or parallelism.
- “Mutexes automatically prevent deadlocks.” Nope—wrong order, same problem.
- “try_lock() solves everything.” It can lead to starvation without careful retry logic. ## Real-World Implementations Banks and trading platforms lock accounts by ascending IDs to keep thousands of concurrent transfers humming. Static analysis tools flag inconsistent lock orders, and languages like Rust let their type system enforce safer concurrency. Could you BE any more careful with your lock order?