168 lines
4.7 KiB
C
168 lines
4.7 KiB
C
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//============================================================================
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// Copyright (c) 1995, Microsoft Corporation
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//
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// File: sync.h
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//
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// History:
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// V Raman July-11-1997 Created.
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//
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// Lock structures and synchronization routines.
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// Lock structures borrowed from RIPv2 by Abolade Gbadegesin.
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// Dynamic locking idea borrowed from RTM by Vadim Eydelman.
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//============================================================================
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#ifndef _SYNC_H_
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#define _SYNC_H_
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//----------------------------------------------------------------------------
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//
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// Read/Write locks for synchronization of access to various lists
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//
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// Given the large number of lists (including the various hash buckets) and
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// the relatively small number of clients that concurrently invoke MGM
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// API, statically allocating a lock structure for each list was
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// considered expensive. Locks are created as needed and stored in a
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// stack structure (implemented as a singly linked list) after use.
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//
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// Subsequent requests for locks are all satisfied by reusing the locks
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// stored on the stack. Only if the stack is empty ie. all locks in the
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// stack are in use are new locks created.
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//
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// This ensures that the most number of locks created is no larger than
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// the maximum number of concurrent clients at any time.
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//
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// csReadWriteBlock - Critical section guarding access to
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// lReaderCount.
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// lReaderCount - Count of readers currently using the
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// shared resource.
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// hReaderDoneEvent - Event on which writers block when readers
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// are currently using the lists.
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// lUseCount - Count of readers + writers. Used to
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// determine if there are any threads waiting
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// on the lock. If there are none the lock
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// can be released to te stack of locks.
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//----------------------------------------------------------------------------
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typedef struct _MGM_READ_WRITE_LOCK
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{
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SINGLE_LIST_ENTRY sleLockList;
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CRITICAL_SECTION csReaderWriterBlock;
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LONG lReaderCount;
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HANDLE hReaderDoneEvent;
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LONG lUseCount;
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} MGM_READ_WRITE_LOCK, *PMGM_READ_WRITE_LOCK;
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//----------------------------------------------------------------------------
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//
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// Read/write locks are created dynamically and stored for
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// reuse in a stack struture.
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//
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//----------------------------------------------------------------------------
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typedef struct _LOCK_LIST
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{
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SINGLE_LIST_ENTRY sleHead;
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CRITICAL_SECTION csListLock;
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BOOL bInit;
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} LOCK_LIST, *PLOCK_LIST;
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//----------------------------------------------------------------------------
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// Standard locked list structure.
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//----------------------------------------------------------------------------
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typedef struct _MGM_LOCKED_LIST
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{
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LIST_ENTRY leHead;
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PMGM_READ_WRITE_LOCK pmrwlLock;
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DWORD dwCreated;
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} MGM_LOCKED_LIST, *PMGM_LOCKED_LIST;
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#define CREATE_LOCKED_LIST( p ) \
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{ \
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(p)-> pmrwlLock = NULL; \
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InitializeListHead( &(p)->leHead ); \
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(p)-> dwCreated = 0x12345678; \
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}
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#define DELETE_LOCKED_LIST( p ) \
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{ \
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(p)-> pmrwlLock = NULL; \
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if ( !IsListEmpty( &(p)-> leHead ) ) \
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TRACE0( ANY, "Locked list being deleted is not empty" ); \
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InitializeListHead( &(p)-> leHead ); \
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(p)-> dwCreated = 0; \
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}
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#define LOCKED_LIST_HEAD( p ) &(p)-> leHead
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//
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// Routines to create/delete locks
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//
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DWORD
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CreateReadWriteLock(
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IN OUT PMGM_READ_WRITE_LOCK * ppmrwl
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);
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VOID
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DeleteReadWriteLock(
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IN OUT PMGM_READ_WRITE_LOCK pmrwl
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);
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VOID
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DeleteLockList(
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);
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//
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// Routines to acquire and release locks.
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//
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DWORD
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AcquireReadLock(
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IN OUT PMGM_READ_WRITE_LOCK * ppmrwl
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);
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VOID
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ReleaseReadLock(
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IN OUT PMGM_READ_WRITE_LOCK * ppmrwl
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);
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DWORD
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AcquireWriteLock(
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IN OUT PMGM_READ_WRITE_LOCK * ppmrwl
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);
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VOID
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ReleaseWriteLock(
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IN OUT PMGM_READ_WRITE_LOCK * ppmrwl
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);
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#endif // _SYNC_H_
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