Module os::task

Task management implementation

Everything about task management, like starting and switching tasks is implemented here.

A single global instance of TaskManager called TASK_MANAGER controls all the tasks in the whole operating system.

A single global instance of Processor called PROCESSOR monitors running task(s) for each core.

A single global instance of PID_ALLOCATOR allocates pid for user apps.

Be careful when you see __switch ASM function in switch.S. Control flow around this function might not be what you expect.

Modules

context 🔒

Implementation of TaskContext

id 🔒

Task pid implementation.

manager 🔒

Implementation of TaskManager

processor 🔒

Implementation of Processor and Intersection of control flow

switch 🔒

Wrap switch.S as a function

task 🔒

Types related to task management & Functions for completely changing TCB

Structs

INITPROC

Creation of initial process

KernelStack

Kernel stack for a process(task)

PidHandle

Abstract structure of PID

Processor

Processor management structure

TaskContext

task context structure containing some registers

TaskControlBlock

Task control block structure

TaskManager

A array of TaskControlBlock that is thread-safe

Enums

TaskStatus

task status: UnInit, Ready, Running, Exited

Constants

IDLE_PID

pid of usertests app in make run TEST=1

Functions

add_initproc

Add init process to the manager

add_task

Add process to ready queue

current_task

Get a copy of the current task

current_trap_cx

Get the mutable reference to trap context of current task

current_user_token

Get the current user token(addr of page table)

exit_current_and_run_next

Exit the current ‘Running’ task and run the next task in task list.

fetch_task

Take a process out of the ready queue

kstack_alloc

allocate a new kernel stack

pid_alloc

Allocate a new PID

run_tasks

The main part of process execution and scheduling Loop fetch_task to get the process that needs to run, and switch the process through __switch

schedule

Return to idle control flow for new scheduling

suspend_current_and_run_next

Suspend the current ‘Running’ task and run the next task in task list.

take_current_task

Get current task through take, leaving a None in its place