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/* lock.h: RECURSIVE LOCKS
*
* $Id$
* Copyright (c) 2001-2020 Ravenbrook Limited. See end of file for license.
*/
#ifndef lock_h
#define lock_h
#include "mpm.h"
#define LockSig ((Sig)0x51970CC9) /* SIGnature LOCK */
/* LockSize -- Return the size of a LockStruct
*
* Supports allocation of locks.
*/
extern size_t LockSize(void);
/* LockInitGlobal -- initialize global locks */
extern void LockInitGlobal(void);
/* LockInit/Finish
*
* lock points to the allocated lock structure. A lock has no
* owner after initialisation.
*/
extern void LockInit(Lock lock);
extern void LockFinish(Lock lock);
/* LockClaimRecursive
*
* This is called to increase the number of claims on the lock.
* LockClaimRecursive will wait until the lock is not owned by another
* thread and return with the lock owned.
* This can be called recursively.
*/
extern void LockClaimRecursive(Lock lock);
/* LockReleaseRecursive
*
* This is called to reduce the number of claims on the lock.
* If the number of claims drops to zero, ownership is relinquished.
* This must not be called without possession of the lock.
*/
extern void LockReleaseRecursive(Lock lock);
/* LockClaim
*
* This may only be used when the lock is not already owned by
* the calling thread.
* When used it behaves like LockClaimRecursive, but must be
* matched by a call to LockRelease.
*/
extern void LockClaim(Lock lock);
/* LockRelease
*
* This must only be used to release a Lock symmetrically
* with LockClaim. It therefore should only be called with
* a single claim.
*/
extern void LockRelease(Lock lock);
/* LockCheck -- Validation */
extern Bool LockCheck(Lock lock);
/* LockIsHeld -- test whether lock is held by any thread */
extern Bool LockIsHeld(Lock lock);
/* == Global locks == */
/* LockClaimGlobalRecursive
*
* This is called to increase the number of claims on the recursive
* global lock. LockClaimRecursive will wait until the lock is not
* owned by another thread and return with the lock owned.
* This can be called recursively.
*/
extern void LockClaimGlobalRecursive(void);
/* LockReleaseGlobalRecursive
*
* This is called to reduce the number of claims on the recursive
* global lock. If the number of claims drops to zero, ownership
* is relinquished. This must not be called without possession of
* the lock.
*/
extern void LockReleaseGlobalRecursive(void);
/* LockClaimGlobal
*
* This is called to claim the binary global lock, and may only be
* used if that lock is not already owned by the calling thread.
* It must be matched by a call to LockReleaseGlobal.
*/
extern void LockClaimGlobal(void);
/* LockReleaseGlobal
*
* This must only be used to release the binary global lock
* symmetrically with LockClaimGlobal.
* It therefore should only be called with a single claim.
*/
extern void LockReleaseGlobal(void);
/* LockSetup -- one-time lock initialization */
extern void LockSetup(void);
#endif /* lock_h */
/* C. COPYRIGHT AND LICENSE
*
* Copyright (C) 2001-2020 Ravenbrook Limited <https://www.ravenbrook.com/>.
*
* 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.
*
* 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 AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR 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.
*/
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