3 Major pieces

Thread management

• create ( pthread_create(thread_returned, attribute_returned, start_routine, args_for_start_routine)
• destroy ( pthread_exit)
  • Threads die when
    • its starting routine returns
    • it calls pthread_exit
    • another thread cancels it with pthread_cancel
    • process dies
    • Note: if main() terminates before its threads do with pthread_exit(), the other threads keep on going; else they die when main() terminates

• see PthreadCreateDemo
• set/get thread attributes ( pthread_attr_init and pthread_attr_destroy)
  • a thread is either joinable (works with pthread_join()) or detached. If it's detached it uses a bit less system resources.
• pthread_self() - get my system thread ID.
• pthread_equal() - compares 2 thread IDs.

Mutex (mutual exclusion) variables

• creating, destroying, locking, unlocking
• set/get mutex attributes
• PthreadMutexDemo

Condition variables

• for comms between threads that share a mutex
• create, destroy, wait and signal
• get/set attributes

Naming Conventions

• pthread_attr_ - thread attribute objects
• pthread_mutex - duh
• pthread_mutexattr_ - mutex attribute objects
• pthead_cond - duh
• pthead_condattr_ - duh
• pthread_key_ - thread-specific data keys (?)

Opaque object

• Used a lot in design of API
• Basic calls work to create or modify opaque objects, attribute funcs deal with opaque attributes

OS Considerations

• Threads run as independent entities in OS, like processes, but 'borrow' parent process' resources
• pthreads_create() around 40-50x faster than fork
• Careful to make sure libs you use are thread safe
• compile with -pthread

Semaphores

• Used for inter-process