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/*
* BIRD Coroutines
*
* (c) 2017 Martin Mares <mj@ucw.cz>
* (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/coro.h"
#include "lib/resource.h"
#include "lib/timer.h"
/* Using a rather big stack for coroutines to allow for stack-local allocations.
* In real world, the kernel doesn't alloc this memory until it is used.
* */
#define CORO_STACK_SIZE 1048576
/*
* Implementation of coroutines based on POSIX threads
*/
#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);
}
void do_lock(struct domain_generic *dg, struct domain_generic **lsp)
{
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");
if (*lsp)
bug("Inconsistent locking stack state on lock");
pthread_mutex_lock(&dg->mutex);
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);
}
/* Coroutines */
struct coroutine {
resource r;
pthread_t id;
pthread_attr_t attr;
void (*entry)(void *);
void *data;
};
static _Thread_local _Bool coro_cleaned_up = 0;
static void coro_free(resource *r)
{
struct coroutine *c = (void *) r;
ASSERT_DIE(pthread_equal(pthread_self(), c->id));
pthread_attr_destroy(&c->attr);
coro_cleaned_up = 1;
}
static struct resclass coro_class = {
.name = "Coroutine",
.size = sizeof(struct coroutine),
.free = coro_free,
};
static void *coro_entry(void *p)
{
struct coroutine *c = p;
ASSERT_DIE(c->entry);
c->entry(c->data);
ASSERT_DIE(coro_cleaned_up);
return NULL;
}
struct coroutine *coro_run(pool *p, void (*entry)(void *), void *data)
{
ASSERT_DIE(entry);
ASSERT_DIE(p);
struct coroutine *c = ralloc(p, &coro_class);
c->entry = entry;
c->data = data;
int e = 0;
if (e = pthread_attr_init(&c->attr))
die("pthread_attr_init() failed: %M", e);
if (e = pthread_attr_setstacksize(&c->attr, CORO_STACK_SIZE))
die("pthread_attr_setstacksize(%u) failed: %M", CORO_STACK_SIZE, e);
if (e = pthread_attr_setdetachstate(&c->attr, PTHREAD_CREATE_DETACHED))
die("pthread_attr_setdetachstate(PTHREAD_CREATE_DETACHED) failed: %M", e);
if (e = pthread_create(&c->id, &c->attr, coro_entry, c))
die("pthread_create() failed: %M", e);
return c;
}
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