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/*
* BIRD Locking
*
* (c) 2020 Maria Matejka <mq@jmq.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#undef LOCAL_DEBUG
#undef DEBUG_LOCKING
#include "lib/birdlib.h"
#include "lib/locking.h"
#include "lib/resource.h"
#include "lib/timer.h"
#include "conf/conf.h"
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdatomic.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
/*
* Locking subsystem
*/
_Thread_local struct lock_order locking_stack = {};
_Thread_local struct domain_generic **last_locked = NULL;
#define ASSERT_NO_LOCK ASSERT_DIE(last_locked == NULL)
struct domain_generic {
pthread_mutex_t mutex;
uint order;
struct domain_generic **prev;
struct lock_order *locked_by;
const char *name;
};
#define DOMAIN_INIT(_name, _order) { .mutex = PTHREAD_MUTEX_INITIALIZER, .name = _name, .order = _order }
static struct domain_generic the_bird_domain_gen = DOMAIN_INIT("The BIRD", OFFSETOF(struct lock_order, the_bird));
DOMAIN(the_bird) the_bird_domain = { .the_bird = &the_bird_domain_gen };
struct domain_generic *
domain_new(const char *name, uint order)
{
ASSERT_DIE(order < sizeof(struct lock_order));
struct domain_generic *dg = xmalloc(sizeof(struct domain_generic));
*dg = (struct domain_generic) DOMAIN_INIT(name, order);
return dg;
}
void
domain_free(struct domain_generic *dg)
{
pthread_mutex_destroy(&dg->mutex);
xfree(dg);
}
const char *
domain_name(struct domain_generic *dg)
{
return dg->name;
}
uint dg_order(struct domain_generic *dg)
{
return dg->order;
}
void do_lock(struct domain_generic *dg, struct domain_generic **lsp)
{
struct lock_order stack_copy;
memcpy(&stack_copy, &locking_stack, sizeof(stack_copy));
struct domain_generic **lll = last_locked;
if ((char *) lsp - (char *) &locking_stack != dg->order)
bug("Trying to lock on bad position: order=%u, lsp=%p, base=%p", dg->order, lsp, &locking_stack);
if (lsp <= last_locked)
bug("Trying to lock in a bad order: %p %p", &stack_copy, lll);
if (*lsp)
bug("Inconsistent locking stack state on lock");
btime lock_begin = current_time();
pthread_mutex_lock(&dg->mutex);
btime duration = current_time() - lock_begin;
if (config && (duration > config->watchdog_warning))
log(L_WARN "Locking of %s took %d ms", dg->name, (int) (duration TO_MS));
if (dg->prev || dg->locked_by)
bug("Previous unlock not finished correctly");
dg->prev = last_locked;
*lsp = dg;
last_locked = lsp;
dg->locked_by = &locking_stack;
}
void do_unlock(struct domain_generic *dg, struct domain_generic **lsp)
{
if ((char *) lsp - (char *) &locking_stack != dg->order)
bug("Trying to unlock on bad position: order=%u, lsp=%p, base=%p", dg->order, lsp, &locking_stack);
if (dg->locked_by != &locking_stack)
bug("Inconsistent domain state on unlock");
if ((last_locked != lsp) || (*lsp != dg))
bug("Inconsistent locking stack state on unlock");
dg->locked_by = NULL;
last_locked = dg->prev;
*lsp = NULL;
dg->prev = NULL;
pthread_mutex_unlock(&dg->mutex);
}
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