Locks are Bad

• taking too few locks
• taking too many locks
• taking the wrong locks
• taking locks in the wrong order
• error recovery
• lost wakeups, erroneous retries

locks do not support modular programming

John Ousterhout: Why Threads are a Bad Idea (for most puroposes) USENIX 1996, http://www.cc.gatech.edu/classes/AY2009/cs4210_fall/papers/ousterhout-threads.pdf