gecko-dev/security/nss/lib/pk11wrap/pk11list.c

/*
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * 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.
 * 
 * The Original Code is the Netscape security libraries.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1994-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s):
 * 
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
 * instead of those above.  If you wish to allow use of your 
 * version of this file only under the terms of the GPL and not to
 * allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by
 * the GPL.  If you do not delete the provisions above, a recipient
 * may use your version of this file under either the MPL or the
 * GPL.
 */
/*
 * Locking and queue management primatives
 *
 */

#include "seccomon.h"
#include "nssilock.h"
#include "prmon.h"
#include "secmod.h"
#include "secmodi.h"
#include "prlong.h"

#define ISREADING 1
#define ISWRITING 2
#define WANTWRITE 4
#define ISLOCKED 3

/*
 * create a new lock for a Module List
 */
SECMODListLock *SECMOD_NewListLock() {
    SECMODListLock *modLock;

    modLock = (SECMODListLock*)PORT_Alloc(sizeof(SECMODListLock));
#ifdef PKCS11_USE_THREADS
    modLock->mutex = NULL;
    modLock->monitor = PZ_NewMonitor(nssILockList);
#else
    modLock->mutex = NULL;
    modLock->monitor = NULL;
#endif
    modLock->state = 0;
    modLock->count = 0;
    return modLock;
}

/*
 * destroy the lock
 */
void SECMOD_DestroyListLock(SECMODListLock *lock) {
    PK11_USE_THREADS(PZ_DestroyMonitor(lock->monitor);)
    PORT_Free(lock);
}


/*
 * Lock the List for Read: NOTE: this assumes the reading isn't so common
 * the writing will be starved.
 */
void SECMOD_GetReadLock(SECMODListLock *modLock) {
#ifdef PKCS11_USE_THREADS
    if (modLock == NULL) return;
    PZ_EnterMonitor(modLock->monitor);
    while (modLock->state & ISWRITING) {
	PZ_Wait(modLock->monitor,PR_INTERVAL_NO_TIMEOUT); /* wait until woken up */
    }
    modLock->state |= ISREADING;
    modLock->count++;
    PZ_ExitMonitor(modLock->monitor);
#endif
}

/*
 * Release the Read lock
 */
void SECMOD_ReleaseReadLock(SECMODListLock *modLock) {
#ifdef PKCS11_USE_THREADS
    if (modLock == NULL) return;
    PZ_EnterMonitor(modLock->monitor);
    modLock->count--;
    if (modLock->count == 0) {
	modLock->state &= ~ISREADING;
	if (modLock->state & WANTWRITE) {
	    PZ_Notify(modLock->monitor);  /* only one writer at a time */
	}
    }
    PZ_ExitMonitor(modLock->monitor);
#endif
}


/*
 * lock the list for Write
 */
void SECMOD_GetWriteLock(SECMODListLock *modLock) {
#ifdef PKCS11_USE_THREADS
    if (modLock == NULL) return;
    PZ_EnterMonitor(modLock->monitor);
    while (modLock->state & ISLOCKED) {
	modLock->state |= WANTWRITE;
	PZ_Wait(modLock->monitor,PR_INTERVAL_NO_TIMEOUT); /* wait until woken up */
    }
    modLock->state = ISWRITING;
    PZ_ExitMonitor(modLock->monitor);
#endif
}


/*
 * Release the Write Lock: NOTE, this code is pretty inefficient if you have
 * lots of write collisions.
 */
void SECMOD_ReleaseWriteLock(SECMODListLock *modLock) {
#ifdef PKCS11_USE_THREADS
    if (modLock == NULL) return;
    PZ_EnterMonitor(modLock->monitor);
    modLock->state = 0;
    PR_NotifyAll(modLock->monitor); /* enable all the readers */
    PZ_ExitMonitor(modLock->monitor);
#endif
}


/*
 * must Hold the Write lock
 */
void
SECMOD_RemoveList(SECMODModuleList **parent, SECMODModuleList *child) {
    *parent = child->next;
    child->next = NULL;
}

/*
 * if lock is not specified, it must already be held
 */
void
SECMOD_AddList(SECMODModuleList *parent, SECMODModuleList *child, 
							SECMODListLock *lock) {
    if (lock) { SECMOD_GetWriteLock(lock); }

    child->next = parent->next;
    parent->next = child;

   if (lock) { SECMOD_ReleaseWriteLock(lock); }
}