LINUX System : Lecture 7 Bong-Soo Sohn Lecture notes acknowledgement : The design of UNIX Operating System

2 Architecture of the UNIX libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs

3 System calls & Libraries libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs system call interface

System calls & Libraries System call library –OS service in the form of C function call Standard library, User library –Linked with the programs at compile time and are part of the user program

5 File Subsystem (1) libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs

6 File Subsystem (2) Managing files and structures of file system Allocating file space Administering free space Controlling access to files Retrieving data for users Interact with set of system calls –open, close, read, write, state, chown, chmod …

7 Buffering Mechanism (1) libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs

8 Buffering Mechanism (2) Interact with block I/O device drivers to initiate data transfer to and from kernel.

9 Process Control Subsystem (1) libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs

10 Process Control Subsystem (2) Managing process structures (proc table, u table,…) Process scheduling Interprocess communication (IPC) Memory management Responsible for process synchronization. Communicate with file subsystem –Loading a file into memory for execution Interact with set of system calls –fork, exec, exit, wait, brk, signal …

11 Process Control Subsystem (3) Memory management module –Control the allocation of memory to a process Scheduler module –Allocate the CPU to processes Interprocess communication –There are several forms.

12 Hardware Control (1) libraries system call interface file subsystem process control subsystem inter-process communication scheduler memory management hardware control hardware buffer cache device drivers characterblock user Level kernel Level hardware Level trap user programs

13 Hardware Control (2) Responsible for handling interrupts and for communicating with the machine. Devices such as disks or terminals may interrupt the CPU while a process is executing

Topics to be covered File subsystem Process control subsystem (Memory Management) Signal IPC (Inter-Process Communication), Synchronization UNIX System Programming (System Calls)

Reference Books The design of the UNIX Operating System, M. J. Bach UNIX Internals : The New Frontiers, U. Vahalia Advanced Programming in the Unix Environment, 2 nd Edition, W. R. Stevens, S. A. Rago