Midterm Topics

• Purpose of an operating system
  • Protecting and synchronizing hardware access
  • Safe sharing of resources
  • Isolation and protection
• Choosing the right interface
  • Policy and mechanism
  • What will the interface require of users?
  • What will the interface require of the implementer?
  • Safety characteristics
  • Performance characteristics
  • Generality
  • Limitations
  • read() and write() as examples
• OS view of the machine
  • Hardware interfaces
  • Privileged execution
  • Interrupts
  • Boot loaders and the bootstrapping process
• Processes
  • Goal: Isolation + Efficiency
  • Process control block
  • Process address space and stacks
  • Run queues and wait queues
  • Parent-child relationships
  • Unix system calls for managing processes
  • Buffering issues
  • Blocking and nonblocking operations
• Threads
  • Efficiency w/o Isolation -- but sometimes more convenient
  • Kernel threads vs. user threads
  • Posix threads API calls for creating and managing threads
• Signals and asynchronous notification
  • Unix system calls
• Scheduling
  • Goals
    • Maximize CPU utilization, throughput
    • Minimize latency: turnaround time, waiting time, response time, user latency
  • Particular schedulers: First Come First Serve, Shortest Job First, Round Robin, Priority
  • Gantt charts
  • Quanta
• Synchronization
  • Race conditions
  • Critical sections/atomic operations
  • Goals: Mutual exclusion, Progress, Starvation Freedom (Fairness)
  • Spinlocks
  • Synchronization objects
    • Mutexes, Recursive Mutexes, Read/Write Locks, Condition Variables, Barriers, Monitors, Semaphores
  • Implementation: Interrupt prevention, atomic instructions
  • Non-blocking I/O
  • Wait-free/lock-free data structures
  • Deadlock
    • Necessary conditions
    • Lock ordering
    • Prevention vs. detection
• Homework
  • WeensyOS 1
  • Lab 1
  • Therac and Flash papers
  • (WeensyOS 2 wouldn't hurt)
• Skills
  • Code analysis
  • Interface analysis ("Choosing the right interface", above)