Agenda

• Announcements
  • Lab 5 continues. Remember, the system() system call is not allowed.
• More Unix Systems Programming
• POSIX Semaphore Implementation

Examples

• pipes
• FreeBSD POSIX semaphore implementation:
  • actual library calls: /usr/src/lib/libc_r/uthread/uthread_sem.c
  • struct sem definition: /usr/src/lib/libc_r/uthread/pthread_private.h
• FreeBSD Pthreads implementations:
  • pthread mutex implementation: /usr/src/lib/libc_r/uthread/uthread_mutex.c
  • pthread condition variable implementation: /usr/src/lib/libc_r/uthread/uthread_cond.c
• System V Semaphores:
  • prodcons-sysvsemaphore example
  • implementation: /usr/src/sys/kern/sysv_sem.c