1.最基本的

最简单的多线程程序，不多说。

 

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

void *print_message_function( void *ptr );

main()
{
     pthread_t thread1, thread2;
     char *message1 = "Thread 1";
     char *message2 = "Thread 2";
     int  iret1, iret2;

    /* Create independent threads each of which will execute function */

     iret1 = pthread_create( &thread1, NULL, print_message_function, (void*) message1);
     iret2 = pthread_create( &thread2, NULL, print_message_function, (void*) message2);

     /* Wait till threads are complete before main continues. Unless we  */
     /* wait we run the risk of executing an exit which will terminate   */
     /* the process and all threads before the threads have completed.   */

     pthread_join( thread1, NULL);
     pthread_join( thread2, NULL); 

     printf("Thread 1 returns: %d\n",iret1);
     printf("Thread 2 returns: %d\n",iret2);
     exit(0);
}

void *print_message_function( void *ptr )
{
     char *message;
     message = (char *) ptr;
     printf("%s \n", message);
}

 

Results:

Thread 1
Thread 2
Thread 1 returns: 0
Thread 2 returns: 0

Details:

• In this example the same function is used in each thread. The arguments are different. The functions need not be the same.

   

• Threads terminate by explicitly calling pthread_exit , by letting the function return, or by a call to the function exit which will terminate the process including any threads.

   

• Function call: pthread_create

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

  Arguments:
  • thread - returns the thread id. (unsigned long int defined in bits/pthreadtypes.h)
  • attr - Set to NULL if default thread attributes are used. (else define members of the struct pthread_attr_t defined in bits/pthreadtypes.h) Attributes include:
    • detached state (joinable? Default: PTHREAD_CREATE_JOINABLE. Other option: PTHREAD_CREATE_DETACHED)
    • scheduling policy (real-time? PTHREAD_INHERIT_SCHED,PTHREAD_EXPLICIT_SCHED,SCHED_OTHER)
    • scheduling parameter
    • inheritsched attribute (Default: PTHREAD_EXPLICIT_SCHED Inherit from parent thread: PTHREAD_INHERIT_SCHED)
    • scope (Kernel threads: PTHREAD_SCOPE_SYSTEM User threads: PTHREAD_SCOPE_PROCESS Pick one or the other not both.)
    • guard size
    • stack address (See unistd.h and bits/posix_opt.h _POSIX_THREAD_ATTR_STACKADDR)
    • stack size (default minimum PTHREAD_STACK_SIZE set in pthread.h),
  • void * (*start_routine) - pointer to the function to be threaded. Function has a single argument: pointer to void.
  • *arg - pointer to argument of function. To pass multiple arguments, send a pointer to a structure.

   

• Function call: pthread_exit

      void pthread_exit(void *retval);
      

  Arguments:
  • retval - Return value of thread.

  This routine kills the thread. The pthread_exit function never returns. If the thread is not detached, the thread id and return value may be examined from another thread by using pthread_join.
  Note: the return pointer *retval , must not be of local scope otherwise it would cease to exist once the thread terminates.