Re: [TOMOYO 05/15](repost) Domain transition handler functions.

Tetsuo Handa
2007-10-15T12:09:23Z

Hello.

James Morris wrote:
> > > It seems that standard kernel list API does not have singly-linked list manipulation.
> > > I'm considering the following list manipulation API.
>
> I'm pretty sure that the singly linked list idea has been rejected a few
> times. Just use the existing API.
>
OK. I posted new one that uses existing API at http://lkml.org/lkml/2007/10/11/140 .

By the way, what do you think of new primitives shown below?
I'd like to use list_for_each_cookie() and list_add_tail_mb() if acceptable.

----- Start of code -----
/********** Existing API **********/

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

static inline void mb(void) {;}
static inline void prefetch(void *p) {;}
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define container_of(ptr, type, member) ({ const typeof( ((type *)0)->member ) *__mptr = (ptr); (type *)( (char *)__mptr - offsetof(type,member) );})
#define list_entry(ptr, type, member) container_of(ptr, type, member)

struct list_head {
struct list_head *next, *prev;
};
#define LIST_HEAD_INIT(name) { &name, &name }
#define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)

/********** Proposed API **********/

/**
* list_for_each_cookie - iterate over a list with cookie.
* @pos: the &struct list_head to use as a loop cursor.
* @cookie: the &struct list_head to use as a cookie.
* @head: the head for your list.
*
* Same with list_for_each except that this primitive uses cookie
* so that we can continue iteration.
*/
#define list_for_each_cookie(pos, cookie, head) \
for ((cookie) || ((cookie) = (head)), pos = (cookie)->next; \
prefetch(pos->next), pos != (head) || ((cookie) = NULL); \
(cookie) = pos, pos = pos->next)

/**
* list_add_tail_mb - add a new entry with memory barrier.
* @new: new entry to be added.
* @head: list head to add it before.
*
* Same with list_add_tail_rcu() except that this primitive uses mb()
* so that we can traverse forwards using list_for_each() and
* list_for_each_cookie().
*/
static inline void list_add_tail_mb(struct list_head *new,
struct list_head *head)
{
struct list_head *prev = head->prev;
struct list_head *next = head;
new->next = next;
new->prev = prev;
mb();
next->prev = new;
prev->next = new;
}

/********** Usage example **********/

struct something {
struct list_head list;
int v;
};

static LIST_HEAD(something_list);

int main(int argc, char *argv[]) {
struct something *ptr;
struct list_head *pos;
struct list_head *cookie = NULL;
int i;
for (i = 0; i < 10; i++) {
printf("add %d\n", i);
ptr = malloc(sizeof(*ptr));
ptr->v = 10 + i;
list_add_tail_mb(&(ptr->list), &something_list);
}
printf("dump\n");
i = 0;
do {
list_for_each_cookie(pos, cookie, &something_list) {
ptr = list_entry(pos, struct something, list);
if (++i % 4 == 0) { /* Interrupt such as buffer-full. */
printf("break\n");
break;
}
printf("%d\n", ptr->v);
}
} while (cookie);
return 0;
}
----- End of code -----

Regards.