POSIX threads or pthreads

Notes

• I believe that these are the standard
• The pthread library is quite large and complex
  • we will only do a basic pass.
• Everything needs to be linked with -lpthread
• pthread_t is the equivalent of pid_t
• Threads are created with pthread_create

  • 
                   int pthread_create(pthread_t *restrict thread,
                              const pthread_attr_t *restrict attr,
                              typeof(void *(void *)) *start_routine,
                              void *restrict arg);

  • thread is the new tid for the thread
  • attr is a null or a list of thread attributes
  • start_routine is a routine to call as the threads "main" function
    • static void * start_routine(void * arg)
  • arg is a pointer to an argument
    • For an int, float, double, ... it could just be the address of the pointer.
    • Or even a nasty cast on each side.
    • For more complex data, we will pass it in a struct.
• When the thread is created it will start executing the start_routine
• When it is finished, the thread should call pthread_exit
  • void pthread_exit(void * retval)
• pthread_self() returns a tid_t
  • In my code I print this out.
  • But I really should not, posix does not guarantee that this is a basic type (ie it could be a struct or class)
• pthread_join
  • int pthread_join(pthread_t thread, void **retval);
  • This is equivalent to wait.
  • But retval contains the address of the return structures.
• Look at pi.cpp
• C++ has a thread library, built on top of pthreads
  • The consturctor takes the starting process and all of theargs
  • The .join method handles join
  • The .joinable method returns if the thread is joinable.
  • There are other methods, but these will do.
• There is much more, but this will do.