CS 3733 Operating Systems

Read Section 6.8 of SG and section 8.4 of PUP

• Implementation of using semaphores (SG pages 186-187)

• Synchronization in Solaris 2:
  • SunOS
    SunOS used critical sections to guard data structures and raised interrupt level as the synchronization mechanism.

  • Solaris 2
    • was designed to support real-time and multiprocessors.
    • for short code segments uses adaptive mutexes:
      • starts as standard semaphore implemented as a spin-lock.
      • If data is locked by a currently running thread, the requesting thread waits
      • If data is locked by a thread not in run state, thread blocks
    • for complex synchronization in long sections of code uses:
      • condition variables - anything long
      • reader-writer locks - items that are accessed frequently but usually only for reading

• System V Semaphores
  • Identification in terms of keys: how do you let other processes know the name of the semaphore?
  • Basic structure and relationship to kernel.
  • Semaphore operations.
  • Semaphore initialization and race conditions.

Skill: Understand how a real operating system might perform internal synchronization.