Mastering Linux Kernel Development

Sequence locks

Conventional reader-writer locks are designed with reader priority, and they might cause a writer task to wait for a non-deterministic duration, which might not be suitable on shared data with time-sensitive updates. This is where sequential lock comes in handy, as it aims at providing a quick and lock-free access to shared resources. Sequential locks are best when the resource that needs to be protected is small and simple, with write access being quick and non-frequent, as internally sequential locks fall back on the spinlock primitive.

Sequential locks introduce a special counter that is incremented every time a writer acquires a sequential lock along with a spinlock. After the writer completes, it releases the spinlock ...