/* lockw3.c: RECURSIVE LOCKS IN WIN32
 *
 * $Id$
 * Copyright (c) 2001 Ravenbrook Limited.  See end of file for license.
 *
 * .design: These are implemented using critical sections.
 *  See the section titled "Synchronization functions" in the Groups
 *  chapter of the Microsoft Win32 API Programmer's Reference.
 *  The "Synchronization" section of the Overview is also relevant.
 *
 *  Critical sections support recursive locking, so the implementation
 *  could be trivial.  This implementation counts the claims to provide
 *  extra checking.
 *
 *  The limit on the number of recursive claims is the max of
 *  ULONG_MAX and the limit imposed by critical sections, which
 *  is believed to be about UCHAR_MAX.
 *
 *  During use the claims field is updated to remember the number of
 *  claims acquired on a lock.  This field must only be modified
 *  while we are inside the critical section.
 */

#include "mpm.h"

#ifndef MPS_OS_W3
#error "lockw3.c is specific to Win32 but MPS_OS_W3 not defined"
#endif

#include "mpswin.h"

SRCID(lockw3, "$Id$");


/* .lock.win32: Win32 lock structure; uses CRITICAL_SECTION */
typedef struct LockStruct {
  Sig sig;                      /* <design/sig/> */
  unsigned long claims;         /* # claims held by the owning thread */
  CRITICAL_SECTION cs;          /* Win32's recursive lock thing */
} LockStruct;


size_t LockSize(void)
{
  return sizeof(LockStruct);
}

Bool LockCheck(Lock lock)
{
  CHECKS(Lock, lock);
  return TRUE;
}

void LockInit(Lock lock)
{
  AVER(lock != NULL);
  lock->claims = 0;
  InitializeCriticalSection(&lock->cs);
  lock->sig = LockSig;
  AVERT(Lock, lock);
}

void LockFinish(Lock lock)
{
  AVERT(Lock, lock);
  /* Lock should not be finished while held */
  AVER(lock->claims == 0);
  DeleteCriticalSection(&lock->cs);
  lock->sig = SigInvalid;
}

void LockClaim(Lock lock)
{
  AVERT(Lock, lock);
  EnterCriticalSection(&lock->cs);
  /* This should be the first claim.  Now we are inside the
   * critical section it is ok to check this. */
  AVER(lock->claims == 0);
  lock->claims = 1;
}

void LockReleaseMPM(Lock lock)
{
  AVERT(Lock, lock);
  AVER(lock->claims == 1);  /* The lock should only be held once */
  lock->claims = 0;  /* Must set this before leaving CS */
  LeaveCriticalSection(&lock->cs);
}

void LockClaimRecursive(Lock lock)
{
  AVERT(Lock, lock);
  EnterCriticalSection(&lock->cs);
  ++lock->claims;
  AVER(lock->claims > 0);
}

void LockReleaseRecursive(Lock lock)
{
  AVERT(Lock, lock);
  AVER(lock->claims > 0);
  --lock->claims;
  LeaveCriticalSection(&lock->cs);
}



/* Global locking is performed by normal locks.
 * A separate lock structure is used for recursive and
 * non-recursive locks so that each may be differently ordered
 * with respect to client-allocated locks.
 */

static LockStruct globalLockStruct;
static LockStruct globalRecLockStruct;
static Lock globalLock = &globalLockStruct;
static Lock globalRecLock = &globalRecLockStruct;
static Bool globalLockInit = FALSE; /* TRUE iff initialized */


static void lockEnsureGlobalLock(void)
{
  /* Ensure both global locks have been initialized. */
  /* There is a race condition initializing them. */
  if (!globalLockInit) {
    LockInit(globalLock);
    LockInit(globalRecLock);
    globalLockInit = TRUE;
  }
}

void LockClaimGlobalRecursive(void)
{
  lockEnsureGlobalLock();
  AVER(globalLockInit);
  LockClaimRecursive(globalRecLock);
}

void LockReleaseGlobalRecursive(void)
{
  AVER(globalLockInit);
  LockReleaseRecursive(globalRecLock);
}

void LockClaimGlobal(void)
{
  lockEnsureGlobalLock();
  AVER(globalLockInit);
  LockClaim(globalLock);
}

void LockReleaseGlobal(void)
{
  AVER(globalLockInit);
  LockReleaseMPM(globalLock);
}


/* C. COPYRIGHT AND LICENSE
 *
 * Copyright (C) 2001-2002 Ravenbrook Limited <http://www.ravenbrook.com/>.
 * All rights reserved.  This is an open source license.  Contact
 * Ravenbrook for commercial licensing options.
 * 
 * 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. Redistributions in any form must be accompanied by information on how
 * to obtain complete source code for this software and any accompanying
 * software that uses this software.  The source code must either be
 * included in the distribution or be available for no more than the cost
 * of distribution plus a nominal fee, and must be freely redistributable
 * under reasonable conditions.  For an executable file, complete source
 * code means the source code for all modules it contains. It does not
 * include source code for modules or files that typically accompany the
 * major components of the operating system on which the executable file
 * runs.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT, ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS AND CONTRIBUTORS 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.
 */