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