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SoftIRQs and tasklets cannot use any blocking instructions as they run in an interrupt context. Workqueues can only be used from a process context. So, I guess if the ISR is long, it can wake up a kernel thread, and let the kernel thread do the dirty work i.e. use blocking instructions.

@Nvidia reject: Thanks for sharing this wealth of questions. What position was this for ?

Sleep or blocking can not be allowed in ISR(Interrupt context), Tasklets(soft interrupt context)
But allowed in WorkQueues(kernel context).

bottom handlers - workqueues but not tasklets.

Bottom halves (SoftIRQ/tasklet/WorkQueue) are the mechanism to push the work from the interrupt handler. They run at later point of time (with interrupts enabled).
Out of these bottom half mechanism, __only__ workqueue is the mechanism
where sleeping is allowed.
So, in this case the sleeping instruction within the interrupt handler can be pushed to the workqueue BH.
Please note that, it is assumed here, that we are talking about, __non_ *threaded* interrupt handlers !

workqueues/threaded irqs

1.request_threaded_irq- > this is newest method and would eventually replace tasklet
2.Tasklet
3.Softirq( not use as they are stattically compiled with kernel)
4.Workqueue
5.kthread

SoftIRQs: can execute in an atomic context
Tasklets: can execute in an atomic context