evthread-internal.h

/*
 * Copyright (c) 2008-2010 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.
 */
#ifndef _EVTHREAD_INTERNAL_H_
#define _EVTHREAD_INTERNAL_H_

#ifdef __cplusplus
extern "C" {
#endif

#include <event2/thread.h>
#include "event-config.h"
#include "util-internal.h"

struct event_base;

#ifndef _EVENT_DISABLE_THREAD_SUPPORT
/* Global function pointers to lock-related functions. NULL if locking isn't
   enabled. */
extern struct evthread_lock_callbacks _evthread_lock_fns;
extern unsigned long (*_evthread_id_fn)(void);
extern int _evthread_lock_debugging_enabled;

/** True iff the given event_base is set up to use locking */
#define EVBASE_USING_LOCKS(base)			\
	(base != NULL && (base)->th_base_lock != NULL)

/** Return the ID of the current thread, or 1 if threading isn't enabled. */
#define EVTHREAD_GET_ID() \
	(_evthread_id_fn ? _evthread_id_fn() : 1)

/** Return true iff we're in the thread that is currently running a given
 * event_base's loop. */
#define EVBASE_IN_THREAD(base)				 \
	(_evthread_id_fn == NULL ||			 \
	(base)->th_owner_id == _evthread_id_fn())

/** Allocate a new lock, and store it in lockvar, a void*.  Sets lockvar to
    NULL if locking is not enabled. */
#define EVTHREAD_ALLOC_LOCK(lockvar, locktype)		\
	((lockvar) = _evthread_lock_fns.alloc ?		\
	    _evthread_lock_fns.alloc(locktype) : NULL)

/** Free a given lock, if it is present and locking is enabled. */
#define EVTHREAD_FREE_LOCK(lockvar, locktype)				\
	do {								\
		void *_lock_tmp_ = (lockvar);				\
		if (_lock_tmp_ && _evthread_lock_fns.free)		\
			_evthread_lock_fns.free(_lock_tmp_, (locktype)); \
	} while (0)

/** Acquire a lock. */
#define EVLOCK_LOCK(lockvar,mode)					\
	do {								\
		if (lockvar)						\
			_evthread_lock_fns.lock(mode, lockvar);		\
	} while (0)

/** Release a lock */
#define EVLOCK_UNLOCK(lockvar,mode)					\
	do {								\
		if (lockvar)						\
			_evthread_lock_fns.unlock(mode, lockvar);	\
	} while (0)

/** Helper: put lockvar1 and lockvar2 into pointerwise ascending order. */
#define _EVLOCK_SORTLOCKS(lockvar1, lockvar2)				\
	do {								\
		if (lockvar1 && lockvar2 && lockvar1 > lockvar2) {	\
			void *tmp = lockvar1;				\
			lockvar1 = lockvar2;				\
			lockvar2 = tmp;					\
		}							\
	} while (0)

/** Acquire both lock1 and lock2.  Always allocates locks in the same order,
 * so that two threads locking two locks with LOCK2 will not deadlock. */
#define EVLOCK_LOCK2(lock1,lock2,mode1,mode2)				\
	do {								\
		void *_lock1_tmplock = (lock1);				\
		void *_lock2_tmplock = (lock2);				\
		_EVLOCK_SORTLOCKS(_lock1_tmplock,_lock2_tmplock);	\
		EVLOCK_LOCK(_lock1_tmplock,mode1);			\
		if (_lock2_tmplock != _lock1_tmplock)			\
			EVLOCK_LOCK(_lock2_tmplock,mode2);		\
	} while (0)

/** Release both lock1 and lock2.  */
#define EVLOCK_UNLOCK2(lock1,lock2,mode1,mode2)				\
	do {								\
		void *_lock1_tmplock = (lock1);				\
		void *_lock2_tmplock = (lock2);				\
		_EVLOCK_SORTLOCKS(_lock1_tmplock,_lock2_tmplock);	\
		if (_lock2_tmplock != _lock1_tmplock)			\
			EVLOCK_UNLOCK(_lock2_tmplock,mode2);		\
		EVLOCK_UNLOCK(_lock1_tmplock,mode1);			\
	} while (0)


/** Lock an event_base, if it is set up for locking.  Acquires the lock
    in the base structure whose field is named 'lockvar'. */
#define EVBASE_ACQUIRE_LOCK(base, lockvar) do {				\
		if (EVBASE_USING_LOCKS(base))				\
			_evthread_lock_fns.lock(0, (base)->lockvar);	\
	} while (0)

/** Unlock an event_base, if it is set up for locking. */
#define EVBASE_RELEASE_LOCK(base, lockvar) do {				\
		if (EVBASE_USING_LOCKS(base))				\
			_evthread_lock_fns.unlock(0, (base)->lockvar);	\
	} while (0)

/** If lock debugging is enabled, and lock is non-null, assert that 'lock' is
 * locked and held by us. */
#define EVLOCK_ASSERT_LOCKED(lock)					\
	do {								\
		if ((lock) && _evthread_lock_debugging_enabled) {	\
			EVUTIL_ASSERT(_evthread_is_debug_lock_held(lock)); \
		}							\
	} while (0)

int _evthread_is_debug_lock_held(void *lock);

/** Try to grab the lock for 'lockvar' without blocking, and return 1 if we
 * manage to get it. */
static inline int EVLOCK_TRY_LOCK(void *lock);
static inline int
EVLOCK_TRY_LOCK(void *lock)
{
	if (lock && _evthread_lock_fns.lock) {
		int r = _evthread_lock_fns.lock(EVTHREAD_TRY, lock);
		return !r;
	} else {
		/* Locking is disabled either globally or for this thing;
		 * of course we count as having the lock. */
		return 1;
	}
}

#else /* _EVENT_DISABLE_THREAD_SUPPORT */

#define EVTHREAD_GET_ID()	1
#define EVTHREAD_ALLOC_LOCK(lockvar, locktype) _EVUTIL_NIL_STMT
#define EVTHREAD_FREE_LOCK(lockvar, locktype) _EVUTIL_NIL_STMT

#define EVLOCK_LOCK(lockvar, mode) _EVUTIL_NIL_STMT
#define EVLOCK_UNLOCK(lockvar, mode) _EVUTIL_NIL_STMT
#define EVLOCK_LOCK2(lock1,lock2,mode1,mode2) _EVUTIL_NIL_STMT
#define EVLOCK_UNLOCK2(lock1,lock2,mode1,mode2) _EVUTIL_NIL_STMT

#define EVBASE_IN_THREAD(base)	1
#define EVBASE_ACQUIRE_LOCK(base, lock) _EVUTIL_NIL_STMT
#define EVBASE_RELEASE_LOCK(base, lock) _EVUTIL_NIL_STMT
#define EVLOCK_ASSERT_LOCKED(lock) _EVUTIL_NIL_STMT

#define EVLOCK_TRY_LOCK(lock) 1
#endif

#ifdef __cplusplus
}
#endif

#endif /* _EVTHREAD_INTERNAL_H_ */