tor-browser

evthread.c (13717B)

---

/*
* Copyright (c) 2008-2012 Niels Provos, Nick Mathewson
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "event2/event-config.h"
#include "evconfig-private.h"

#ifndef EVENT__DISABLE_THREAD_SUPPORT

#include "event2/thread.h"

#include <stdlib.h>
#include <string.h>

#include "log-internal.h"
#include "mm-internal.h"
#include "util-internal.h"
#include "evthread-internal.h"

#ifdef EVTHREAD_EXPOSE_STRUCTS
#define GLOBAL
#else
#define GLOBAL static
#endif

#ifndef EVENT__DISABLE_DEBUG_MODE
extern int event_debug_created_threadable_ctx_;
extern int event_debug_mode_on_;
#endif

/* globals */
GLOBAL int evthread_lock_debugging_enabled_ = 0;
GLOBAL struct evthread_lock_callbacks evthread_lock_fns_ = {
0, 0, NULL, NULL, NULL, NULL
};
GLOBAL unsigned long (*evthread_id_fn_)(void) = NULL;
GLOBAL struct evthread_condition_callbacks evthread_cond_fns_ = {
0, NULL, NULL, NULL, NULL
};

/* Used for debugging */
static struct evthread_lock_callbacks original_lock_fns_ = {
0, 0, NULL, NULL, NULL, NULL
};
static struct evthread_condition_callbacks original_cond_fns_ = {
0, NULL, NULL, NULL, NULL
};

void
evthread_set_id_callback(unsigned long (*id_fn)(void))
{
evthread_id_fn_ = id_fn;
}

struct evthread_lock_callbacks *evthread_get_lock_callbacks()
{
return evthread_lock_debugging_enabled_
    ? &original_lock_fns_ : &evthread_lock_fns_;
}
struct evthread_condition_callbacks *evthread_get_condition_callbacks()
{
return evthread_lock_debugging_enabled_
    ? &original_cond_fns_ : &evthread_cond_fns_;
}
void evthreadimpl_disable_lock_debugging_(void)
{
evthread_lock_debugging_enabled_ = 0;
}

int
evthread_set_lock_callbacks(const struct evthread_lock_callbacks *cbs)
{
struct evthread_lock_callbacks *target = evthread_get_lock_callbacks();

#ifndef EVENT__DISABLE_DEBUG_MODE
if (event_debug_mode_on_) {
	if (event_debug_created_threadable_ctx_) {
	    event_errx(1, "evthread initialization must be called BEFORE anything else!");
	}
}
#endif

if (!cbs) {
	if (target->alloc)
		event_warnx("Trying to disable lock functions after "
		    "they have been set up will probaby not work.");
	memset(target, 0, sizeof(evthread_lock_fns_));
	return 0;
}
if (target->alloc) {
	/* Uh oh; we already had locking callbacks set up.*/
	if (target->lock_api_version == cbs->lock_api_version &&
		target->supported_locktypes == cbs->supported_locktypes &&
		target->alloc == cbs->alloc &&
		target->free == cbs->free &&
		target->lock == cbs->lock &&
		target->unlock == cbs->unlock) {
		/* no change -- allow this. */
		return 0;
	}
	event_warnx("Can't change lock callbacks once they have been "
	    "initialized.");
	return -1;
}
if (cbs->alloc && cbs->free && cbs->lock && cbs->unlock) {
	memcpy(target, cbs, sizeof(evthread_lock_fns_));
	return event_global_setup_locks_(1);
} else {
	return -1;
}
}

int
evthread_set_condition_callbacks(const struct evthread_condition_callbacks *cbs)
{
struct evthread_condition_callbacks *target = evthread_get_condition_callbacks();

#ifndef EVENT__DISABLE_DEBUG_MODE
if (event_debug_mode_on_) {
	if (event_debug_created_threadable_ctx_) {
	    event_errx(1, "evthread initialization must be called BEFORE anything else!");
	}
}
#endif

if (!cbs) {
	if (target->alloc_condition)
		event_warnx("Trying to disable condition functions "
		    "after they have been set up will probaby not "
		    "work.");
	memset(target, 0, sizeof(evthread_cond_fns_));
	return 0;
}
if (target->alloc_condition) {
	/* Uh oh; we already had condition callbacks set up.*/
	if (target->condition_api_version == cbs->condition_api_version &&
		target->alloc_condition == cbs->alloc_condition &&
		target->free_condition == cbs->free_condition &&
		target->signal_condition == cbs->signal_condition &&
		target->wait_condition == cbs->wait_condition) {
		/* no change -- allow this. */
		return 0;
	}
	event_warnx("Can't change condition callbacks once they "
	    "have been initialized.");
	return -1;
}
if (cbs->alloc_condition && cbs->free_condition &&
    cbs->signal_condition && cbs->wait_condition) {
	memcpy(target, cbs, sizeof(evthread_cond_fns_));
}
if (evthread_lock_debugging_enabled_) {
	evthread_cond_fns_.alloc_condition = cbs->alloc_condition;
	evthread_cond_fns_.free_condition = cbs->free_condition;
	evthread_cond_fns_.signal_condition = cbs->signal_condition;
}
return 0;
}

#define DEBUG_LOCK_SIG	0xdeb0b10c

struct debug_lock {
unsigned signature;
unsigned locktype;
unsigned long held_by;
/* XXXX if we ever use read-write locks, we will need a separate
 * lock to protect count. */
int count;
void *lock;
};

static void *
debug_lock_alloc(unsigned locktype)
{
struct debug_lock *result = mm_malloc(sizeof(struct debug_lock));
if (!result)
	return NULL;
if (original_lock_fns_.alloc) {
	if (!(result->lock = original_lock_fns_.alloc(
			locktype|EVTHREAD_LOCKTYPE_RECURSIVE))) {
		mm_free(result);
		return NULL;
	}
} else {
	result->lock = NULL;
}
result->signature = DEBUG_LOCK_SIG;
result->locktype = locktype;
result->count = 0;
result->held_by = 0;
return result;
}

static void
debug_lock_free(void *lock_, unsigned locktype)
{
struct debug_lock *lock = lock_;
EVUTIL_ASSERT(lock->count == 0);
EVUTIL_ASSERT(locktype == lock->locktype);
EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
if (original_lock_fns_.free) {
	original_lock_fns_.free(lock->lock,
	    lock->locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
}
lock->lock = NULL;
lock->count = -100;
lock->signature = 0x12300fda;
mm_free(lock);
}

static void
evthread_debug_lock_mark_locked(unsigned mode, struct debug_lock *lock)
{
EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
++lock->count;
if (!(lock->locktype & EVTHREAD_LOCKTYPE_RECURSIVE))
	EVUTIL_ASSERT(lock->count == 1);
if (evthread_id_fn_) {
	unsigned long me;
	me = evthread_id_fn_();
	if (lock->count > 1)
		EVUTIL_ASSERT(lock->held_by == me);
	lock->held_by = me;
}
}

static int
debug_lock_lock(unsigned mode, void *lock_)
{
struct debug_lock *lock = lock_;
int res = 0;
if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
	EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
else
	EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
if (original_lock_fns_.lock)
	res = original_lock_fns_.lock(mode, lock->lock);
if (!res) {
	evthread_debug_lock_mark_locked(mode, lock);
}
return res;
}

static void
evthread_debug_lock_mark_unlocked(unsigned mode, struct debug_lock *lock)
{
EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
if (lock->locktype & EVTHREAD_LOCKTYPE_READWRITE)
	EVUTIL_ASSERT(mode & (EVTHREAD_READ|EVTHREAD_WRITE));
else
	EVUTIL_ASSERT((mode & (EVTHREAD_READ|EVTHREAD_WRITE)) == 0);
if (evthread_id_fn_) {
	unsigned long me;
	me = evthread_id_fn_();
	EVUTIL_ASSERT(lock->held_by == me);
	if (lock->count == 1)
		lock->held_by = 0;
}
--lock->count;
EVUTIL_ASSERT(lock->count >= 0);
}

static int
debug_lock_unlock(unsigned mode, void *lock_)
{
struct debug_lock *lock = lock_;
int res = 0;
evthread_debug_lock_mark_unlocked(mode, lock);
if (original_lock_fns_.unlock)
	res = original_lock_fns_.unlock(mode, lock->lock);
return res;
}

static int
debug_cond_wait(void *cond_, void *lock_, const struct timeval *tv)
{
int r;
struct debug_lock *lock = lock_;
EVUTIL_ASSERT(lock);
EVUTIL_ASSERT(DEBUG_LOCK_SIG == lock->signature);
EVLOCK_ASSERT_LOCKED(lock_);
evthread_debug_lock_mark_unlocked(0, lock);
r = original_cond_fns_.wait_condition(cond_, lock->lock, tv);
evthread_debug_lock_mark_locked(0, lock);
return r;
}

/* misspelled version for backward compatibility */
void
evthread_enable_lock_debuging(void)
{
evthread_enable_lock_debugging();
}

void
evthread_enable_lock_debugging(void)
{
struct evthread_lock_callbacks cbs = {
	EVTHREAD_LOCK_API_VERSION,
	EVTHREAD_LOCKTYPE_RECURSIVE,
	debug_lock_alloc,
	debug_lock_free,
	debug_lock_lock,
	debug_lock_unlock
};
if (evthread_lock_debugging_enabled_)
	return;
memcpy(&original_lock_fns_, &evthread_lock_fns_,
    sizeof(struct evthread_lock_callbacks));
memcpy(&evthread_lock_fns_, &cbs,
    sizeof(struct evthread_lock_callbacks));

memcpy(&original_cond_fns_, &evthread_cond_fns_,
    sizeof(struct evthread_condition_callbacks));
evthread_cond_fns_.wait_condition = debug_cond_wait;
evthread_lock_debugging_enabled_ = 1;

/* XXX return value should get checked. */
event_global_setup_locks_(0);
}

int
evthread_is_debug_lock_held_(void *lock_)
{
struct debug_lock *lock = lock_;
if (! lock->count)
	return 0;
if (evthread_id_fn_) {
	unsigned long me = evthread_id_fn_();
	if (lock->held_by != me)
		return 0;
}
return 1;
}

void *
evthread_debug_get_real_lock_(void *lock_)
{
struct debug_lock *lock = lock_;
return lock->lock;
}

void *
evthread_setup_global_lock_(void *lock_, unsigned locktype, int enable_locks)
{
/* there are four cases here:
   1) we're turning on debugging; locking is not on.
   2) we're turning on debugging; locking is on.
   3) we're turning on locking; debugging is not on.
   4) we're turning on locking; debugging is on. */

if (!enable_locks && original_lock_fns_.alloc == NULL) {
	/* Case 1: allocate a debug lock. */
	EVUTIL_ASSERT(lock_ == NULL);
	return debug_lock_alloc(locktype);
} else if (!enable_locks && original_lock_fns_.alloc != NULL) {
	/* Case 2: wrap the lock in a debug lock. */
	struct debug_lock *lock;
	EVUTIL_ASSERT(lock_ != NULL);

	if (!(locktype & EVTHREAD_LOCKTYPE_RECURSIVE)) {
		/* We can't wrap it: We need a recursive lock */
		original_lock_fns_.free(lock_, locktype);
		return debug_lock_alloc(locktype);
	}
	lock = mm_malloc(sizeof(struct debug_lock));
	if (!lock) {
		original_lock_fns_.free(lock_, locktype);
		return NULL;
	}
	lock->lock = lock_;
	lock->locktype = locktype;
	lock->count = 0;
	lock->held_by = 0;
	return lock;
} else if (enable_locks && ! evthread_lock_debugging_enabled_) {
	/* Case 3: allocate a regular lock */
	EVUTIL_ASSERT(lock_ == NULL);
	return evthread_lock_fns_.alloc(locktype);
} else {
	/* Case 4: Fill in a debug lock with a real lock */
	struct debug_lock *lock = lock_ ? lock_ : debug_lock_alloc(locktype);
	EVUTIL_ASSERT(enable_locks &&
	              evthread_lock_debugging_enabled_);
	EVUTIL_ASSERT(lock->locktype == locktype);
	if (!lock->lock) {
		lock->lock = original_lock_fns_.alloc(
			locktype|EVTHREAD_LOCKTYPE_RECURSIVE);
		if (!lock->lock) {
			lock->count = -200;
			mm_free(lock);
			return NULL;
		}
	}
	return lock;
}
}


#ifndef EVTHREAD_EXPOSE_STRUCTS
unsigned long
evthreadimpl_get_id_()
{
return evthread_id_fn_ ? evthread_id_fn_() : 1;
}
void *
evthreadimpl_lock_alloc_(unsigned locktype)
{
#ifndef EVENT__DISABLE_DEBUG_MODE
if (event_debug_mode_on_) {
	event_debug_created_threadable_ctx_ = 1;
}
#endif

return evthread_lock_fns_.alloc ?
    evthread_lock_fns_.alloc(locktype) : NULL;
}
void
evthreadimpl_lock_free_(void *lock, unsigned locktype)
{
if (evthread_lock_fns_.free)
	evthread_lock_fns_.free(lock, locktype);
}
int
evthreadimpl_lock_lock_(unsigned mode, void *lock)
{
if (evthread_lock_fns_.lock)
	return evthread_lock_fns_.lock(mode, lock);
else
	return 0;
}
int
evthreadimpl_lock_unlock_(unsigned mode, void *lock)
{
if (evthread_lock_fns_.unlock)
	return evthread_lock_fns_.unlock(mode, lock);
else
	return 0;
}
void *
evthreadimpl_cond_alloc_(unsigned condtype)
{
#ifndef EVENT__DISABLE_DEBUG_MODE
if (event_debug_mode_on_) {
	event_debug_created_threadable_ctx_ = 1;
}
#endif

return evthread_cond_fns_.alloc_condition ?
    evthread_cond_fns_.alloc_condition(condtype) : NULL;
}
void
evthreadimpl_cond_free_(void *cond)
{
if (evthread_cond_fns_.free_condition)
	evthread_cond_fns_.free_condition(cond);
}
int
evthreadimpl_cond_signal_(void *cond, int broadcast)
{
if (evthread_cond_fns_.signal_condition)
	return evthread_cond_fns_.signal_condition(cond, broadcast);
else
	return 0;
}
int
evthreadimpl_cond_wait_(void *cond, void *lock, const struct timeval *tv)
{
if (evthread_cond_fns_.wait_condition)
	return evthread_cond_fns_.wait_condition(cond, lock, tv);
else
	return 0;
}
int
evthreadimpl_is_lock_debugging_enabled_(void)
{
return evthread_lock_debugging_enabled_;
}

int
evthreadimpl_locking_enabled_(void)
{
return evthread_lock_fns_.lock != NULL;
}
#endif

#endif