Around Scheduler

Scheduler invoked by
Hardware Interrupts
Software Interrupts
SoftIrq     -> softirq daemon.(priority 19).
Tasklets   -> Register the tasklet(ie add to the tasklet list).
                     can be executed only on one cpu(using TASKLET_STATE_RUN).
                     TASKLET_STATE_SCHED -> registered and ready to run.
Workqueues  -> Run in user context.
For each workqueue kernel generates the kernel daemon in whose context deferred tasks are performed.
For each workqueue , a thread can be created on every CPU of the system.

Waiting for events to occur
Waitqueues  -> When process are put to sleep using wait_event , you ensure that a corresponding wake_up call at another point in the kernel.
Completion