[beatle]

yeah pthreads is implemented using futex. I don't care about the implementation details. It doesn't matter since it's still lock-based (albeit more efficient due to fewer system calls). My original point is, threading is still lock-based. Replacing your lock-based code with queues eliminates many of the penalties associated with locks and also simplifies your remaining code. Instead of using a lock to protect a shared resource, you can instead create a queue to serialize the tasks that access that resource. Queues do not impose the same penalties as locks. For example, queueing a task does not require trapping into the kernel to acquire a mutex (or however mutex is implemented)

[jrockway]

Acquiring a mutex on Linux involves reading an integer from memory.

Also, the way a queue prevents two consumers from popping off the same element is the same way a mutex is implemented.