/** @file * MS COM / XPCOM Abstraction Layer - Automatic locks, implementation. */ /* * Copyright (C) 2006-2020 Oracle Corporation * * This file is part of VirtualBox Open Source Edition (OSE), as * available from http://www.virtualbox.org. This file is free software; * you can redistribute it and/or modify it under the terms of the GNU * General Public License (GPL) as published by the Free Software * Foundation, in version 2 as it comes in the "COPYING" file of the * VirtualBox OSE distribution. VirtualBox OSE is distributed in the * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. * * The contents of this file may alternatively be used under the terms * of the Common Development and Distribution License Version 1.0 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the * VirtualBox OSE distribution, in which case the provisions of the * CDDL are applicable instead of those of the GPL. * * You may elect to license modified versions of this file under the * terms and conditions of either the GPL or the CDDL or both. */ #ifndef VBOX_INCLUDED_com_AutoLock_h #define VBOX_INCLUDED_com_AutoLock_h #ifndef RT_WITHOUT_PRAGMA_ONCE # pragma once #endif #include /** @defgroup grp_com_autolock Automatic Locks * @ingroup grp_com * @{ */ // macros for automatic lock validation; these will amount to nothing // unless lock validation is enabled for the runtime #if defined(RT_LOCK_STRICT) # define VBOX_WITH_MAIN_LOCK_VALIDATION # define COMMA_LOCKVAL_SRC_POS , RT_SRC_POS # define LOCKVAL_SRC_POS_DECL RT_SRC_POS_DECL # define COMMA_LOCKVAL_SRC_POS_DECL , RT_SRC_POS_DECL # define LOCKVAL_SRC_POS_ARGS RT_SRC_POS_ARGS # define COMMA_LOCKVAL_SRC_POS_ARGS , RT_SRC_POS_ARGS #else # define COMMA_LOCKVAL_SRC_POS # define LOCKVAL_SRC_POS_DECL # define COMMA_LOCKVAL_SRC_POS_DECL # define LOCKVAL_SRC_POS_ARGS # define COMMA_LOCKVAL_SRC_POS_ARGS #endif namespace util { //////////////////////////////////////////////////////////////////////////////// // // Order classes for lock validation // //////////////////////////////////////////////////////////////////////////////// /** * IPRT now has a sophisticated system of run-time locking classes to validate * locking order. Since the Main code is handled by simpler minds, we want * compile-time constants for simplicity, and we'll look up the run-time classes * in AutoLock.cpp transparently. These are passed to the constructors of the * LockHandle classes. */ enum VBoxLockingClass { LOCKCLASS_NONE = 0, LOCKCLASS_WEBSERVICE = 1, // highest order: webservice locks LOCKCLASS_VIRTUALBOXOBJECT = 2, // highest order within Main itself: VirtualBox object lock LOCKCLASS_HOSTOBJECT = 3, // Host object lock LOCKCLASS_LISTOFMACHINES = 4, // list of machines in VirtualBox object LOCKCLASS_MACHINEOBJECT = 5, // Machine object lock LOCKCLASS_SNAPSHOTOBJECT = 6, // snapshot object locks // (the snapshots tree, including the child pointers in Snapshot, // is protected by the normal Machine object lock) LOCKCLASS_MEDIUMQUERY = 7, // lock used to protect Machine::queryInfo LOCKCLASS_LISTOFMEDIA = 8, // list of media (hard disks, DVDs, floppies) in VirtualBox object LOCKCLASS_LISTOFOTHEROBJECTS = 9, // any other list of objects LOCKCLASS_OTHEROBJECT = 10, // any regular object member variable lock LOCKCLASS_PROGRESSLIST = 11, // list of progress objects in VirtualBox; no other object lock // may be held after this! LOCKCLASS_OBJECTSTATE = 12 // object state lock (handled by AutoCaller classes) }; void InitAutoLockSystem(); /** * Check whether the current thread holds any locks in the given class * * @return true if any such locks are held, false otherwise. If the lock * validator is not compiled in, always returns false. * @param lockClass Which lock class to check. */ bool AutoLockHoldsLocksInClass(VBoxLockingClass lockClass); //////////////////////////////////////////////////////////////////////////////// // // LockHandle and friends // //////////////////////////////////////////////////////////////////////////////// /** * Abstract base class for semaphore handles (RWLockHandle and WriteLockHandle). * Don't use this directly, but this implements lock validation for them. */ class LockHandle { public: LockHandle() {} virtual ~LockHandle() {} /** * Returns @c true if the current thread holds a write lock on this * read/write semaphore. Intended for debugging only. */ virtual bool isWriteLockOnCurrentThread() const = 0; /** * Returns @c true if the current thread holds a read lock on this * read/write semaphore. Intended for debugging only as it isn't always * accurate given @a fWannaHear. */ virtual bool isReadLockedOnCurrentThread(bool fWannaHear = true) const = 0; /** * Returns the current write lock level of this semaphore. The lock level * determines the number of nested #lockWrite() calls on the given * semaphore handle. * * Note that this call is valid only when the current thread owns a write * lock on the given semaphore handle and will assert otherwise. */ virtual uint32_t writeLockLevel() const = 0; virtual void lockWrite(LOCKVAL_SRC_POS_DECL) = 0; virtual void unlockWrite() = 0; virtual void lockRead(LOCKVAL_SRC_POS_DECL) = 0; virtual void unlockRead() = 0; #ifdef VBOX_WITH_MAIN_LOCK_VALIDATION virtual const char* describe() const = 0; #endif private: // prohibit copy + assignment LockHandle(const LockHandle&); LockHandle& operator=(const LockHandle&); }; /** * Full-featured read/write semaphore handle implementation. * * This is an auxiliary base class for classes that need full-featured * read/write locking as described in the AutoWriteLock class documentation. * Instances of classes inherited from this class can be passed as arguments to * the AutoWriteLock and AutoReadLock constructors. */ class RWLockHandle : public LockHandle { public: RWLockHandle(VBoxLockingClass lockClass); virtual ~RWLockHandle(); virtual bool isWriteLockOnCurrentThread() const; virtual bool isReadLockedOnCurrentThread(bool fWannaHear = true) const; virtual void lockWrite(LOCKVAL_SRC_POS_DECL); virtual void unlockWrite(); virtual void lockRead(LOCKVAL_SRC_POS_DECL); virtual void unlockRead(); virtual uint32_t writeLockLevel() const; #ifdef VBOX_WITH_MAIN_LOCK_VALIDATION virtual const char* describe() const; #endif private: struct Data; Data *m; DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(RWLockHandle); /* Shuts up MSC warning C4625. */ }; /** * Write-only semaphore handle implementation. * * This is an auxiliary base class for classes that need write-only (exclusive) * locking and do not need read (shared) locking. This implementation uses a * cheap and fast critical section for both lockWrite() and lockRead() methods * which makes a lockRead() call fully equivalent to the lockWrite() call and * therefore makes it pointless to use instahces of this class with * AutoReadLock instances -- shared locking will not be possible anyway and * any call to lock() will block if there are lock owners on other threads. * * Use with care only when absolutely sure that shared locks are not necessary. */ class WriteLockHandle : public LockHandle { public: WriteLockHandle(VBoxLockingClass lockClass); virtual ~WriteLockHandle(); virtual bool isWriteLockOnCurrentThread() const; virtual bool isReadLockedOnCurrentThread(bool fWannaHear = true) const; virtual void lockWrite(LOCKVAL_SRC_POS_DECL); virtual void unlockWrite(); virtual void lockRead(LOCKVAL_SRC_POS_DECL); virtual void unlockRead(); virtual uint32_t writeLockLevel() const; #ifdef VBOX_WITH_MAIN_LOCK_VALIDATION virtual const char* describe() const; #endif private: struct Data; Data *m; DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(WriteLockHandle); /* Shuts up MSC warning C4625. */ }; //////////////////////////////////////////////////////////////////////////////// // // Lockable // //////////////////////////////////////////////////////////////////////////////// /** * Lockable interface. * * This is an abstract base for classes that need read/write locking. Unlike * RWLockHandle and other classes that makes the read/write semaphore a part of * class data, this class allows subclasses to decide which semaphore handle to * use. */ class Lockable { public: virtual ~Lockable() { } /* To make VC++ 2019 happy. */ /** * Returns a pointer to a LockHandle used by AutoWriteLock/AutoReadLock * for locking. Subclasses are allowed to return @c NULL -- in this case, * the AutoWriteLock/AutoReadLock object constructed using an instance of * such subclass will simply turn into no-op. */ virtual LockHandle *lockHandle() const = 0; /** * Equivalent to #lockHandle()->isWriteLockOnCurrentThread(). * Returns @c false if lockHandle() returns @c NULL. */ bool isWriteLockOnCurrentThread() { LockHandle *h = lockHandle(); return h ? h->isWriteLockOnCurrentThread() : false; } /** * Equivalent to #lockHandle()->isReadLockedOnCurrentThread(). * Returns @c false if lockHandle() returns @c NULL. * @note Use with care, simple debug assertions and similar only. */ bool isReadLockedOnCurrentThread(bool fWannaHear = true) const { LockHandle *h = lockHandle(); return h ? h->isReadLockedOnCurrentThread(fWannaHear) : false; } }; //////////////////////////////////////////////////////////////////////////////// // // AutoLockBase // //////////////////////////////////////////////////////////////////////////////// /** * Abstract base class for all autolocks. * * This cannot be used directly. Use AutoReadLock or AutoWriteLock or AutoMultiWriteLock2/3 * which directly and indirectly derive from this. * * In the implementation, the instance data contains a list of lock handles. * The class provides some utility functions to help locking and unlocking * them. */ class AutoLockBase { protected: AutoLockBase(uint32_t cHandles COMMA_LOCKVAL_SRC_POS_DECL); AutoLockBase(uint32_t cHandles, LockHandle *pHandle COMMA_LOCKVAL_SRC_POS_DECL); virtual ~AutoLockBase(); struct Data; Data *m; virtual void callLockImpl(LockHandle &l) = 0; virtual void callUnlockImpl(LockHandle &l) = 0; void callLockOnAllHandles(); void callUnlockOnAllHandles(); void cleanup(); public: void acquire(); void release(); private: // prohibit copy + assignment AutoLockBase(const AutoLockBase&); AutoLockBase& operator=(const AutoLockBase&); }; //////////////////////////////////////////////////////////////////////////////// // // AutoReadLock // //////////////////////////////////////////////////////////////////////////////// /** * Automatic read lock. Use this with a RWLockHandle to request a read/write * semaphore in read mode. You can also use this with a WriteLockHandle but * that makes little sense since they treat read mode like write mode. * * If constructed with a RWLockHandle or an instance of Lockable (which in * practice means any VirtualBoxBase derivative), it autoamtically requests * the lock in read mode and releases the read lock in the destructor. */ class AutoReadLock : public AutoLockBase { public: /** * Constructs a null instance that does not manage any read/write * semaphore. * * Note that all method calls on a null instance are no-ops. This allows to * have the code where lock protection can be selected (or omitted) at * runtime. */ AutoReadLock(LOCKVAL_SRC_POS_DECL) : AutoLockBase(1, NULL COMMA_LOCKVAL_SRC_POS_ARGS) { } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a read lock. */ AutoReadLock(LockHandle *aHandle COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(1, aHandle COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a read lock. */ AutoReadLock(LockHandle &aHandle COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(1, &aHandle COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a read lock. */ AutoReadLock(const Lockable &aLockable COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(1, aLockable.lockHandle() COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a read lock. */ AutoReadLock(const Lockable *aLockable COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(1, aLockable ? aLockable->lockHandle() : NULL COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } virtual ~AutoReadLock(); virtual void callLockImpl(LockHandle &l); virtual void callUnlockImpl(LockHandle &l); private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoReadLock); /* Shuts up MSC warning C4625. */ }; //////////////////////////////////////////////////////////////////////////////// // // AutoWriteLockBase // //////////////////////////////////////////////////////////////////////////////// /** * Base class for all auto write locks. * * This cannot be used directly. Use AutoWriteLock or AutoMultiWriteLock2/3 * which derive from this. * * It has some utility methods for subclasses. */ class AutoWriteLockBase : public AutoLockBase { protected: AutoWriteLockBase(uint32_t cHandles COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(cHandles COMMA_LOCKVAL_SRC_POS_ARGS) { } AutoWriteLockBase(uint32_t cHandles, LockHandle *pHandle COMMA_LOCKVAL_SRC_POS_DECL) : AutoLockBase(cHandles, pHandle COMMA_LOCKVAL_SRC_POS_ARGS) { } virtual ~AutoWriteLockBase() { } virtual void callLockImpl(LockHandle &l); virtual void callUnlockImpl(LockHandle &l); private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoWriteLockBase); /* Shuts up MSC warning C4625. */ }; //////////////////////////////////////////////////////////////////////////////// // // AutoWriteLock // //////////////////////////////////////////////////////////////////////////////// /** * Automatic write lock. Use this with a RWLockHandle to request a read/write * semaphore in write mode. There can only ever be one writer of a read/write * semaphore: while the lock is held in write mode, no other writer or reader * can request the semaphore and will block. * * If constructed with a RWLockHandle or an instance of Lockable (which in * practice means any VirtualBoxBase derivative), it autoamtically requests * the lock in write mode and releases the write lock in the destructor. * * When used with a WriteLockHandle, it requests the semaphore contained therein * exclusively. */ class AutoWriteLock : public AutoWriteLockBase { public: /** * Constructs a null instance that does not manage any read/write * semaphore. * * Note that all method calls on a null instance are no-ops. This allows to * have the code where lock protection can be selected (or omitted) at * runtime. */ AutoWriteLock(LOCKVAL_SRC_POS_DECL) : AutoWriteLockBase(1, NULL COMMA_LOCKVAL_SRC_POS_ARGS) { } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a write lock. */ AutoWriteLock(LockHandle *aHandle COMMA_LOCKVAL_SRC_POS_DECL) : AutoWriteLockBase(1, aHandle COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a write lock. */ AutoWriteLock(LockHandle &aHandle COMMA_LOCKVAL_SRC_POS_DECL) : AutoWriteLockBase(1, &aHandle COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a write lock. */ AutoWriteLock(const Lockable &aLockable COMMA_LOCKVAL_SRC_POS_DECL) : AutoWriteLockBase(1, aLockable.lockHandle() COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a write lock. */ AutoWriteLock(const Lockable *aLockable COMMA_LOCKVAL_SRC_POS_DECL) : AutoWriteLockBase(1, aLockable ? aLockable->lockHandle() : NULL COMMA_LOCKVAL_SRC_POS_ARGS) { acquire(); } /** * Constructs a new instance that will start managing the given read/write * semaphore by requesting a write lock. */ AutoWriteLock(uint32_t cHandles, LockHandle** pHandles COMMA_LOCKVAL_SRC_POS_DECL); /** * Release all write locks acquired by this instance through the #acquire() * call and destroys the instance. * * Note that if there there are nested #acquire() calls without the * corresponding number of #release() calls when the destructor is called, it * will assert. This is because having an unbalanced number of nested locks * is a program logic error which must be fixed. */ virtual ~AutoWriteLock() { cleanup(); } void attach(LockHandle *aHandle); /** @see attach (LockHandle *) */ void attach(LockHandle &aHandle) { attach(&aHandle); } /** @see attach (LockHandle *) */ void attach(const Lockable &aLockable) { attach(aLockable.lockHandle()); } /** @see attach (LockHandle *) */ void attach(const Lockable *aLockable) { attach(aLockable ? aLockable->lockHandle() : NULL); } bool isWriteLockOnCurrentThread() const; uint32_t writeLockLevel() const; bool isReadLockedOnCurrentThread(bool fWannaHear = true) const; private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoWriteLock); /* Shuts up MSC warning C4625. */ }; //////////////////////////////////////////////////////////////////////////////// // // AutoMultiWriteLock* // //////////////////////////////////////////////////////////////////////////////// /** * A multi-write-lock containing two other write locks. * */ class AutoMultiWriteLock2 : public AutoWriteLockBase { public: AutoMultiWriteLock2(Lockable *pl1, Lockable *pl2 COMMA_LOCKVAL_SRC_POS_DECL); AutoMultiWriteLock2(LockHandle *pl1, LockHandle *pl2 COMMA_LOCKVAL_SRC_POS_DECL); virtual ~AutoMultiWriteLock2() { cleanup(); } private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoMultiWriteLock2); /* Shuts up MSC warning C4625. */ }; /** * A multi-write-lock containing three other write locks. * */ class AutoMultiWriteLock3 : public AutoWriteLockBase { public: AutoMultiWriteLock3(Lockable *pl1, Lockable *pl2, Lockable *pl3 COMMA_LOCKVAL_SRC_POS_DECL); AutoMultiWriteLock3(LockHandle *pl1, LockHandle *pl2, LockHandle *pl3 COMMA_LOCKVAL_SRC_POS_DECL); virtual ~AutoMultiWriteLock3() { cleanup(); } private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoMultiWriteLock3); /* Shuts up MSC warning C4625. */ }; /** * A multi-write-lock containing four other write locks. * */ class AutoMultiWriteLock4 : public AutoWriteLockBase { public: AutoMultiWriteLock4(Lockable *pl1, Lockable *pl2, Lockable *pl3, Lockable *pl4 COMMA_LOCKVAL_SRC_POS_DECL); AutoMultiWriteLock4(LockHandle *pl1, LockHandle *pl2, LockHandle *pl3, LockHandle *pl4 COMMA_LOCKVAL_SRC_POS_DECL); virtual ~AutoMultiWriteLock4() { cleanup(); } private: DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(AutoMultiWriteLock4); /* Shuts up MSC warning C4625. */ }; } /* namespace util */ /** @} */ #endif /* !VBOX_INCLUDED_com_AutoLock_h */ /* vi: set tabstop=4 shiftwidth=4 expandtab: */