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113 lines
3.0 KiB
C++
113 lines
3.0 KiB
C++
/*
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* PROGRAM: JRD Access Method
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* MODULE: GlobalRWLock.h
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* DESCRIPTION: Global Read Write Lock
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*
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* The contents of this file are subject to the Initial
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* Developer's Public License Version 1.0 (the "License");
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* you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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* http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_idpl.
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*
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* Software distributed under the License is distributed AS IS,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied.
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* See the License for the specific language governing rights
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* and limitations under the License.
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*
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* The Original Code was created by Nickolay Samofatov
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* for the Firebird Open Source RDBMS project.
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*
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* Copyright (c) 2006 Nickolay Samofatov
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* and all contributors signed below.
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*
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* All Rights Reserved.
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* Contributor(s):
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*
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* Roman Simakov <roman-simakov@users.sourceforge.net>
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*
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*/
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#ifndef GLOBAL_RW_LOCK
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#define GLOBAL_RW_LOCK
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#include "../common/classes/alloc.h"
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#include "../jrd/jrd.h"
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#include "../jrd/lck.h"
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#include "../jrd/lck_proto.h"
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#include "fb_types.h"
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#include "os/pio.h"
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#include "../common/classes/condition.h"
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//#define COS_DEBUG
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#ifdef COS_DEBUG
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DEFINE_TRACE_ROUTINE(cos_trace);
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#define COS_TRACE(args) cos_trace args
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#define COS_TRACE_AST(message) gds__trace(message)
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#else
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#define COS_TRACE(args) /* nothing */
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#define COS_TRACE_AST(message) /* nothing */
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#endif
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namespace Jrd {
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enum lck_t;
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class GlobalRWLock : public Firebird::PermanentStorage
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{
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public:
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GlobalRWLock(thread_db* tdbb, MemoryPool& p,
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lck_t lckType, bool lock_caching = true,
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FB_SIZE_T lockLen = 0, const UCHAR* lockStr = NULL);
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virtual ~GlobalRWLock();
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// This function returns false if it cannot take the lock
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bool lockWrite(thread_db* tdbb, SSHORT wait);
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void unlockWrite(thread_db* tdbb, const bool release = false);
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bool lockRead(thread_db* tdbb, SSHORT wait, const bool queueJump = false);
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void unlockRead(thread_db* tdbb);
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bool tryReleaseLock(thread_db* tdbb);
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void shutdownLock(thread_db* tdbb);
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protected:
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// Flag to indicate that somebody is waiting via lock manager.
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// If somebody uses lock manager, all concurrent requests should also
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// go via lock manager to prevent starvation.
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Lock* cachedLock;
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// Load the object from shared location.
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virtual bool fetch(thread_db* /*tdbb*/) { return true; }
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virtual void invalidate(thread_db* /*tdbb*/)
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{
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fb_assert(readers == 0);
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blocking = false;
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}
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virtual void blockingAstHandler(thread_db* tdbb);
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Firebird::Mutex counterMutex; // Protects counter and blocking flag
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private:
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ULONG pendingLock;
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ULONG readers;
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Firebird::Condition noReaders; // Semaphore to wait all readers unlock to start relock
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ULONG pendingWriters;
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bool currentWriter;
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Firebird::Condition writerFinished;
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// true - unlock keep cached lock and release by AST.
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// false - unlock releases cached lock if possible
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bool lockCaching;
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bool blocking; // Unprocessed AST pending
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static int blocking_ast_cached_lock(void* ast_object);
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};
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}
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#endif // GLOBAL_RW_LOCK
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