5.6.3. Deferring work

• motivation: we can't do all work in the irq handler (for now at least -> PREEMPT_RT can run irqs as kthreads)

• available mechanisms
  • very old: bottom halves
  • deprecated but available: tasklets (disadvantages: run in softirq context -> must be atomic, no userspace access, high prio -> block userspace process, etc)
  • state of art: workqueues