bird/nest/locks.c
Martin Mares f545d38707 Added universal locking mechanism which will solve problems
with protocols wanting to use the same port on the same interface
during reconfiguration time.

How to use locks: In the if_notify hook, just order locks for the
interfaces you want to work with and do the real socket opening after the
lock hook function gets called. When you stop using the socket, close
it and rfree() the lock.

Please update your protocols to use the new locking mechanism.
1999-12-09 18:54:20 +00:00

147 lines
2.8 KiB
C

/*
* BIRD Object Locks
*
* (c) 1999 Martin Mares <mj@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include <stdio.h>
#define LOCAL_DEBUG
#include "nest/bird.h"
#include "lib/resource.h"
#include "nest/locks.h"
#include "nest/iface.h"
static list olock_list;
static event *olock_event;
static inline int
olock_same(struct object_lock *x, struct object_lock *y)
{
return
x->type == y->type &&
x->iface == y->iface &&
x->port == y->port &&
ipa_equal(x->addr, y->addr);
}
static void
olock_free(resource *r)
{
struct object_lock *q, *l = (struct object_lock *) r;
node *n;
DBG("olock: Freeing %p\n", l);
switch (l->state)
{
case OLOCK_STATE_FREE:
break;
case OLOCK_STATE_LOCKED:
case OLOCK_STATE_EVENT:
rem_node(&l->n);
n = HEAD(l->waiters);
if (n->next)
{
DBG("olock: -> %p becomes locked\n", n);
q = SKIP_BACK(struct object_lock, n, n);
rem_node(n);
add_tail_list(&l->waiters, &q->waiters);
q->state = OLOCK_STATE_EVENT;
add_head(&olock_list, n);
ev_schedule(olock_event);
}
break;
case OLOCK_STATE_WAITING:
rem_node(&l->n);
break;
default:
ASSERT(0);
}
}
static void
olock_dump(resource *r)
{
struct object_lock *l = (struct object_lock *) r;
static char *olock_states[] = { "free", "locked", "waiting", "event" };
debug("(%d:%s:%I:%d) [%s]", l->type, (l->iface ? l->iface->name : "?"), l->addr, l->port, olock_states[l->state]);
if (!EMPTY_LIST(l->waiters))
debug(" [wanted]\n");
}
static struct resclass olock_class = {
"ObjLock",
sizeof(struct object_lock),
olock_free,
olock_dump
};
struct object_lock *
olock_new(pool *p)
{
struct object_lock *l = ralloc(p, &olock_class);
l->state = OLOCK_STATE_FREE;
init_list(&l->waiters);
return l;
}
void
olock_acquire(struct object_lock *l)
{
node *n;
struct object_lock *q;
WALK_LIST(n, olock_list)
{
q = SKIP_BACK(struct object_lock, n, n);
if (olock_same(q, l))
{
l->state = OLOCK_STATE_WAITING;
add_tail(&q->waiters, &l->n);
DBG("olock: %p waits\n", l);
return;
}
}
DBG("olock: %p acquired immediately\n", l);
l->state = OLOCK_STATE_EVENT;
add_head(&olock_list, &l->n);
ev_schedule(olock_event);
}
int
olock_run_event(void *unused)
{
node *n;
struct object_lock *q;
DBG("olock: Processing events\n");
for(;;)
{
n = HEAD(olock_list);
if (!n->next)
break;
q = SKIP_BACK(struct object_lock, n, n);
if (q->state != OLOCK_STATE_EVENT)
break;
DBG("olock: %p locked\n", q);
q->state = OLOCK_STATE_LOCKED;
rem_node(&q->n);
add_tail(&olock_list, &q->n);
q->hook(q);
}
return 0;
}
void
olock_init(void)
{
DBG("olock: init\n");
init_list(&olock_list);
olock_event = ev_new(&root_pool);
olock_event->hook = olock_run_event;
}