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 PidAllocator called 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
• manager 🔒
  Implementation of TaskManager
• pid 🔒
  Implementation of PidAllocator
• processor 🔒
  Implementation of Processor and Intersection of control flow
• switch 🔒
  Wrap switch.S as a function
• task 🔒
  Implementation of TaskControlBlock

Structs

• INITPROC
  Globle process that init user shell
• KernelStack
  Kernelstack for app
• PidAllocator
  Pid Allocator struct
• PidHandle
  Bind pid lifetime to PidHandle
• Processor
  Processor management structure
• TaskContext
  task context structure containing some registers
• TaskManager
  A array of TaskControlBlock that is thread-safe

Constants

• IDLE_PID
  pid of usertests app in make run TEST=1

Functions

• add_initproc
  Add init process to the manager
• add_task
  Interface offered to add task
• current_task
  Get running task
• current_trap_cx
  Get the mutable reference to trap context of current task
• current_user_token
  Get token of the address space of current task
• exit_current_and_run_next
  Exit the current ‘Running’ task and run the next task in task list.
• fetch_task
  Interface offered to pop the first task
• pid_alloc
  Allocate a pid from PID_ALLOCATOR
• 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
  Take the current task,leaving a None in its place