Convering fork-->vfork()

[Zulu]

Hi all. I have some code which does what i need it to do on a standard Linux platform. However i need to make it work on the uClinux kernel, which is used for microcontrollers. To do this, i have been told i will need to change fork() to vfork().

If someone would be able to help me, or guide me on how to make this work on uClinux using the vfork(), i would appreciate it.

Here is the code:

#include <stdio.h>																		
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <signal.h>

void termination_handler(int);

int test_pipe=1;
int main()
{
	int pipedescriptor[2]; 															
	char buff[100];																				
	alarm(10);																		
	/*if (signal (SIGALRM, termination_handler) == SIG_IGN)*/
        signal (SIGALRM, termination_handler);										
       		
	pipe(pipedescriptor);
	while (test_pipe>0)																
	{						
		if(!fork())										
		{
			printf("This is the child writing to the pipe\n");
			write(pipedescriptor[1], "TST", 4);										
			printf("This is the child exiting the pipe\n");
			exit(0);
				
		}
		else
		{
			printf("This is the parent reading from the pipe\n");
			fflush(stdout);
			read(pipedescriptor[0], buff, 4);										 			
			printf("Parent reading form pipe: \"%s\"\n", buff);
			test_pipe++;															
			wait(NULL);
		}
	}
	while(1);
	return 0;
}

void termination_handler (int signum)												
{
	printf("Total messeges sent: %d\n",test_pipe);
	printf("Total bytes per second: %d\n",(test_pipe*4)/10);
	exit(0);
}

Any help is appreciated.

[Salem]

So does this mean you've already tried to use 'vfork()' and it's failed horribly?

How about - http://www.linuxjournal.com/article/7221

This is avoided by ensuring that the child never returns from the current stack frame once vfork() has been called and that it calls _exit when finishing-exit cannot be called as it changes data structures in the parent.

You're going to get a lot more detailed (and accurate) help by signing up to the forums / mailing lists at http://www.uclinux.org/

[brewbuck]

Hi all. I have some code which does what i need it to do on a standard Linux platform. However i need to make it work on the uClinux kernel, which is used for microcontrollers. To do this, i have been told i will need to change fork() to vfork().

If someone would be able to help me, or guide me on how to make this work on uClinux using the vfork(), i would appreciate it.

In the code you posted, you can't. vfork() suspends the parent until the child either exits or execs. This is to avoid the page-copy penalty on systems that can't support copy-on-write. Your program will have to be redesigned. The child will have to reside in a separate program. You will vfork() and then the child will exec() this program.