Quelle  evthread.c   Sprache: C

/*
 * 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