C++

Forum

 
Segmentation fault (core dumped) when using clone() system call

binladenvn88 (18)
I'm trying write small test code using clone() system call.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
/*
 * test.c
 */
#include <stdio.h>
#include <stdlib.h>
#include <linux/sched.h>

struct shared_data_struct {
        unsigned int data1;
        unsigned int data2;
};

struct shared_data_struct shared_data;

static int inc_second(struct shared_data_struct *);

int main(){

        int i, j, pid;
        void *child_stack;

        /* allocate memory for other process to execute in */
        if((child_stack = (void *) malloc(4096)) == NULL) {
                perror("Cannot allocate stack for child");
                exit(1);
        }

        /* clone process and run in the same memory space */
        if ((pid = clone((void *)&inc_second, child_stack,
                        CLONE_VM, &shared_data)) < 0) {
                perror("clone called failed.");
                exit(1);
        }

        /* increment first member of shared struct */
        for (j = 0; j < 2000; j++) {
                for (i = 0; i < 100000; i++) {
                        shared_data.data1++;
                }
        }

        return 0;
}

int inc_second(struct shared_data_struct *sd)
{
        int i,j;

        /* increment second member of shared struct */
        for (j = 1; j < 2000; j++) {
                for (i = 1; i < 100000; i++) {
                        sd->data2++;
                }
        }
}


Compile above source code has not any warning or error.

$ gcc -o test test.c

But, when i run this program, i have gotten error message:

Segmentation fault (core dumped)

I really don't know why have this error?
Please suggest for me solve this problem.
Thank so much!
Last edited on
kbw (9488)
Shortcuts cost time.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
#include <stdio.h>
#include <stdlib.h>
#include <linux/sched.h>

struct shared_data_struct
{
	unsigned long data1;
	unsigned long data2;
};

struct shared_data_struct shared_data;

static int inc_second(struct shared_data_struct *);

int main()
{
	int i, j, pid;
	void *child_stack;

	/* allocate memory for other process to execute in */
	child_stack = (void *) malloc(4096);
	if (child_stack == NULL)
	{
		perror("Cannot allocate stack for child");
		exit(1);
	}

	/* clone process and run in the same memory space */
	pid = clone((void *)&inc_second, child_stack, CLONE_VM, &shared_data);
	if (pid < 0)
	{
		perror("clone called failed.");
		exit(1);
	}

	/* increment first member of shared struct */
	for (j = 0; j < 2000; ++j)
		for (i = 0; i < 100000; ++i)
			++shared_data.data1;

	sleep(10);	/* let things settle down */
	printf("%lu %lu\n", shared_data.data1, shared_data.data2);

	return 0;
}

int inc_second(struct shared_data_struct *sd)
{
	int i,j;

	/* increment second member of shared struct */
	for (j = 1; j < 2000; ++j)
		for (i = 1; i < 100000; ++i)
			++(sd->data2);
}

binladenvn88 (18)
Thank you for reply, but perhap have some thing wrong. After compile above source code of you successfully, i have gotten same error "Segmentation fault (core dumped)" when run program.
I'm running on Ubuntu 12.04, gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Could you have suggest for me to solve this problem,
Thank you so much!
Last edited on
kbw (9488)
Mine runs ok (using an up to date ArchLinux), both in and outside of gdb. I'll take another look when I get onto a Linux box.
binladenvn88 (18)
Thank you, but my program require run on Ubuntu or Debian, and now i can't found error anywhere, ^_^,
Last edited on
kbw (9488)
You may find this article useful.
http://www.linuxjournal.com/article/5211?page=0,0
Topic archived. No new replies allowed.