/*
* %CopyrightBegin%
*
* Copyright Ericsson AB 1997-2009. All Rights Reserved.
*
* The contents of this file are subject to the Erlang Public License,
* Version 1.1, (the "License"); you may not use this file except in
* compliance with the License. You should have received a copy of the
* Erlang Public License along with this software. If not, it can be
* retrieved online at http://www.erlang.org/.
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* %CopyrightEnd%
*
*/
/*
* common interface to some simple synchronisation primitives for
* internal use by ei.
*/
/* Note that these locks are NOT recursive on Win32 or Solaris,
* i.e. self-deadlock will occur if a thread tries to obtain a lock it
* is already holding. The primitives used on VxWorks are recursive however.
*/
#include "eidef.h"
#ifdef __WIN32__
#include <winsock2.h>
#include <windows.h>
#include <winbase.h>
#elif VXWORKS
#include <vxWorks.h>
#include <semLib.h>
#else /* unix */
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#endif /* platforms */
#include "ei_malloc.h"
#include "ei_locking.h"
#ifdef _REENTRANT
/*
* Create a new mutex object.
* Returns a pointer to the mutex if successful, NULL otherwise.
*/
ei_mutex_t *ei_mutex_create(void)
{
ei_mutex_t *l;
if ((l = ei_malloc(sizeof(*l))) == NULL) return NULL;
#ifdef __WIN32__
l->lock = CreateMutex(NULL,FALSE,NULL);
#elif VXWORKS
if (!(l->lock = semMCreate(SEM_DELETE_SAFE))) {
ei_free(l);
return NULL;
}
#else /* unix */
l->lock = ei_m_create();
#endif
return l;
}
/*
* Free a mutex and the structure asociated with it.
*
* This function attempts to obtain the mutex before releasing it;
* If nblock == 1 and the mutex was unavailable, the function will
* return failure and the mutex will not have been removed.
*
* If nblock == 0 the function will block until the mutex becomes
* available, at which time it will be removed and the function will
* succeed.
*
* returns 0 if the mutex is removed, -1 on failure (busy)
*/
int ei_mutex_free(ei_mutex_t *l, int nblock)
{
/* attempt to lock it first, to make sure it's really free */
if (ei_mutex_lock(l,nblock)) return -1; /* attempt failed */
/* we are now holding the lock */
#ifdef __WIN32__
CloseHandle(l->lock);
#elif VXWORKS
if (semDelete(l->lock) == ERROR) return -1;
#else /* unix */
ei_m_destroy(l->lock);
#endif
ei_free(l);
return 0;
}
/* Grab a mutex. If the mutex is not held by any other process the
* function returns so that the caller may enter a critical section.
* Processes subsequently wishing to obtain the lock will block
* until this process releases it.
*
* If the mutex is busy (held by some other process) and nblock == 0,
* the function will block until the mutex is freed by the process
* holding it, returning only when the mutex has been grabbed.
*
* If the mutex is busy and nblock != 0, the function will not block.
* Instead it will return -1 immediately, indicating that the
* operation failed.
* Returns 0 on success, -1 on failure.
*/
int ei_mutex_lock(ei_mutex_t *l, int nblock)
{
#ifdef __WIN32__
/* check valid values for timeout: is 0 ok? */
if (WaitForSingleObject(l->lock,(nblock? 0 : INFINITE)) != WAIT_OBJECT_0)
return -1;
#elif VXWORKS
if (semTake(l->lock,(nblock? NO_WAIT : WAIT_FOREVER)) == ERROR)
return -1;
#else /* unix */
if (nblock) {
if (ei_m_trylock(l->lock) < 0) return -1;
}
else ei_m_lock(l->lock);
#endif
return 0;
}
/* Release a mutex */
int ei_mutex_unlock(ei_mutex_t *l)
{
#ifdef __WIN32__
ReleaseMutex(l->lock);
#elif VXWORKS
semGive(l->lock);
#else /* unix */
ei_m_unlock(l->lock);
#endif
return 0;
}
#endif /* _REENTRANT */
