Why spinlocks are used in interrupt handlers

Question

I would like to know why spin locks are used instead of semaphores inside an interrupt handler.

Answer 1

Semaphores cause tasks to sleep on contention, which is unacceptable for interrupt handlers. Basically, for such a short and fast task (interrupt handling) the work carried out by the semaphore is overkill. Also, spinlocks can't be held by more than one task.