How Processes Are Organized

The runqueue list groups all processes in a task_running state. When it comes to grouping processes in other states, the various states call for different types of treatment, with Linux opting for one of the choices shown in the following list.

• Processes in a task_stopped or in a task_zombie state are not linked in specific lists. There is no need to group processes in either of these two states, since stopped and zombie processes are accessed only via PID or via linked lists of the child processes for a particular parent.

• Processes in a task_interruptible or task_uninterruptible state are subdivided into many classes, each of which corresponds to a specific event. In this case, the process state does not provide enough information to retrieve the process quickly, so it is necessary to introduce additional lists of processes. These are called wait queues.

Continue reading here: Wait queues

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