[gsliepen]

Indeed. Also, spinlocks are not that great in userlang where one thread can preempt another thread that is holding a spinlock, which means threads on other cores that also want that lock would spin for a whole timeslice and burn a huge amount of cycles.

In the kernel, spinlocks are typically taken at the same time IRQs for the current core are disabled, which avoids this issue (and deadlocks of course).

[afr0ck]

You don't have to disable IRQs if the spinlock is never taken by an interrupt handler. Disabling preemption would be enough in such a case, and that reduces latency issues related to disabling IRQs.