Thread Creation

• Each thread in a process is identified by a thread ID, type pthread_t.
• Upon creation, each thread executes a thread function. This is just an ordinary function and contains the code that the thread should run. When the function returns, the thread exits.
• The pthread_create function creates a new thread. You provide it with the following:
  • A pointer to a pthread_t variable, in which the thread ID of the new thread is stored.
  • A pointer to a thread attribute object. This object controls details of how the thread interacts with the rest of the program. If you pass NULL as the thread attribute, a thread will be created with the default thread attributes.
  • A pointer to the thread function. This is an ordinary function pointer, of this type:

    void* (*) (void*)
    

  • A thread argument value of type void*. Whatever you pass is simply passed as the argument to the thread function when the thread begins executing.
• A call to pthread_create returns immediately, and the original thread continues executing the instructions following the call. Meanwhile, the new thread begins executing the thread function. Linux schedules both threads asynchronously. http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/thread-create.cthread-create.c (see Fig. 5.1)

  Figure 5.1: Create a Thread

  
• Under normal circumstances, a thread exits in one of two ways;
  • by returning from the thread function. The return value from the thread function is taken to be the return value of the thread.
  • a thread can exit explicitly by calling pthread_exit.