simple_processes.c

linux下多线程程序设计,包括signals,mutex,simple_once

/********************************************************
 * An example source module to accompany...
 *
 * "Using POSIX Threads: Programming with Pthreads"
 *     by Brad nichols, Dick Buttlar, Jackie Farrell
 *     O'Reilly & Associates, Inc.
 *
 ********************************************************
 * simple_processes.c
 *
 * Simple multi-process example.
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <errno.h>  

void do_one_thing(int *);
void do_another_thing(int *);
void do_wrap_up(int, int);

int   shared_mem_id;
int   *shared_mem_ptr;
int   *r1p;
int   *r2p;

extern int main(void)
{
	pid_t  child1_pid, child2_pid;
	int  status;
	
	/* initialize shared memory segment */
	if ((shared_mem_id = shmget(IPC_PRIVATE, 2*sizeof(int), 0660)) == -1)
		perror("shmget"), exit(1);
	if ((shared_mem_ptr = (int *)shmat(shared_mem_id, (void *)0, 0)) == (void *)-1)
		perror("shmat failed"), exit(1);
	
	r1p = shared_mem_ptr;  
	r2p = (shared_mem_ptr + 1);
	
	*r1p = 0;
	*r2p = 0;
	
	if ((child1_pid = fork()) == 0) 
	{
		/* first child */
		do_one_thing(r1p);
		return 0;
	} 
	else if (child1_pid == -1) 
	{
		perror("fork"), exit(1);
	}
	
	/* parent */
	if ((child2_pid = fork()) == 0) 
	{
		/* second child */
		do_another_thing(r2p);
		return 0;
	} 
	else if (child2_pid == -1) 
	{  
		perror("fork"), exit(1);
	}
	
	/* parent */
	if ((waitpid(child1_pid, &status, 0) == -1))
		perror("waitpid"), exit(1);
	if ((waitpid(child2_pid, &status, 0) == -1))
		perror("waitpid"), exit(1);
	
	do_wrap_up(*r1p, *r2p);
	
	return 0; 
}

void do_one_thing(int *pnum_times)
{
	int i, j, x;
	
	for (i = 0;  i < 4; i++) 
	{
		printf("doing one thing\n"); 
		for (j = 0; j < 10000; j++) 
			x = x + i;
		(*pnum_times)++;
	}
}

void do_another_thing(int *pnum_times)
{
	int i, j, x;
	
	for (i = 0;  i < 4; i++) 
	{
		printf("doing another \n"); 
		for (j = 0; j < 10000; j++) 
			x = x + i;
		(*pnum_times)++;
	}
}

void do_wrap_up(int one_times, int another_times)
{
	int total;
	
	total = one_times + another_times;
	printf("All done, one thing %d, another %d for a total of %d\n", one_times, another_times, total);
}