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/*
* 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

/* 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;
}

int
evthread_set_lock_callbacks(const struct evthread_lock_callbacks *cbs)
{
struct evthread_lock_callbacks *target =
evthread_lock_debugging_enabled_
? &original_lock_fns_ : &evthread_lock_fns_;

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_lock_debugging_enabled_
? &original_cond_fns_ : &evthread_cond_fns_;

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_;
EVUTIL_ASSERT(enable_locks &&
evthread_lock_debugging_enabled_);
EVUTIL_ASSERT(lock->locktype == locktype);
EVUTIL_ASSERT(lock->lock == NULL);
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)
{
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)
{
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
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