Locker, which cannot be used to lock/unlock resources and just returns true for checks for whether a particular resource is locked. More...

#include <locker_noop.h>

Inheritance diagram for mongo::LockerNoop:

Detailed Description

Locker, which cannot be used to lock/unlock resources and just returns true for checks for whether a particular resource is locked.

Do not use it for cases where actual locking behaviour is expected or locking is performed.

Public Member Functions
	LockerNoop ()

virtual bool	isNoop () const
	Returns true if this is an instance of LockerNoop. More...

virtual ClientState	getClientState () const
	Return whether client is holding any locks (active), or is queued on any locks or waiting for a ticket (throttled). More...

virtual LockerId	getId () const

stdx::thread::id	getThreadId () const override
	Get a platform-specific thread identifier of the thread which owns the this locker for tracing purposes. More...

void	updateThreadIdToCurrentThread () override
	Updates any cached thread id values to represent the current thread. More...

void	unsetThreadId () override
	Clears any cached thread id values. More...

void	setSharedLocksShouldTwoPhaseLock (bool sharedLocksShouldTwoPhaseLock) override
	Indicate that shared locks should participate in two-phase locking for this Locker instance. More...

void	setMaxLockTimeout (Milliseconds maxTimeout) override
	This is useful to ensure that potential deadlocks do not occur. More...

bool	hasMaxLockTimeout () override
	Returns whether this Locker has a maximum lock timeout set. More...

void	unsetMaxLockTimeout () override
	Clears the max lock timeout override set by setMaxLockTimeout() above. More...

virtual LockResult	lockGlobal (OperationContext *opCtx, LockMode mode)
	This should be the first method invoked for a particular Locker object. More...

virtual LockResult	lockGlobal (LockMode mode)

virtual LockResult	lockGlobalBegin (OperationContext *opCtx, LockMode mode, Date_t deadline)
	Requests the global lock to be acquired in the specified mode. More...

virtual LockResult	lockGlobalBegin (LockMode mode, Date_t deadline)

virtual LockResult	lockGlobalComplete (OperationContext *opCtx, Date_t deadline)
	Calling lockGlobalComplete without an OperationContext does not allow the lock acquisition to be interrupted. More...

virtual LockResult	lockGlobalComplete (Date_t deadline)

virtual void	lockMMAPV1Flush ()
	This method is used only in the MMAP V1 storage engine, otherwise it is a no-op. More...

virtual bool	unlockGlobal ()
	Decrements the reference count on the global lock. More...

virtual void	downgradeGlobalXtoSForMMAPV1 ()
	This is only necessary for the MMAP V1 engine and in particular, the fsyncLock command which needs to first acquire the global lock in X-mode for truncating the journal and then downgrade to S before it blocks. More...

virtual void	beginWriteUnitOfWork ()
	beginWriteUnitOfWork/endWriteUnitOfWork are called at the start and end of WriteUnitOfWorks. More...

virtual void	endWriteUnitOfWork ()

virtual bool	inAWriteUnitOfWork () const

virtual LockResult	lock (OperationContext *opCtx, ResourceId resId, LockMode mode, Date_t deadline, bool checkDeadlock)
	Acquires lock on the specified resource in the specified mode and returns the outcome of the operation. More...

virtual LockResult	lock (ResourceId resId, LockMode mode, Date_t deadline, bool checkDeadlock)
	Calling lock without an OperationContext does not allow LOCK_WAITING states to be interrupted. More...

virtual void	downgrade (ResourceId resId, LockMode newMode)
	Downgrades the specified resource's lock mode without changing the reference count. More...

virtual bool	unlock (ResourceId resId)
	Releases a lock previously acquired through a lock call. More...

virtual LockMode	getLockMode (ResourceId resId) const
	Retrieves the mode in which a lock is held or checks whether the lock held for a particular resource covers the specified mode. More...

virtual bool	isLockHeldForMode (ResourceId resId, LockMode mode) const

virtual bool	isDbLockedForMode (StringData dbName, LockMode mode) const

virtual bool	isCollectionLockedForMode (StringData ns, LockMode mode) const

virtual ResourceId	getWaitingResource () const
	Returns the resource that this locker is waiting/blocked on (if any). More...

virtual void	getLockerInfo (LockerInfo *lockerInfo) const

virtual boost::optional< LockerInfo >	getLockerInfo () const
	Returns boost::none if this is an instance of LockerNoop, or a populated LockerInfo otherwise. More...

virtual bool	saveLockStateAndUnlock (LockSnapshot *stateOut)
	Retrieves all locks held by this transaction, other than RESOURCE_MUTEX locks, and what mode they're held in. More...

virtual void	restoreLockState (OperationContext *opCtx, const LockSnapshot &stateToRestore)
	Re-locks all locks whose state was stored in 'stateToRestore'. More...

virtual void	restoreLockState (const LockSnapshot &stateToRestore)

virtual void	releaseTicket ()
	Releases the ticket associated with the Locker. More...

virtual void	reacquireTicket (OperationContext *opCtx)
	Reacquires a ticket for the Locker. More...

virtual void	dump () const

virtual bool	isW () const

virtual bool	isR () const

virtual bool	isLocked () const

virtual bool	isWriteLocked () const

virtual bool	isReadLocked () const

virtual bool	hasLockPending () const
	Pending means we are currently trying to get a lock (could be the parallel batch writer lock). More...

bool	isGlobalLockedRecursively () override

Public Member Functions inherited from mongo::Locker
virtual	~Locker ()

void	setShouldConflictWithSecondaryBatchApplication (bool newValue)
	If set to false, this opts out of conflicting with replication's use of the ParallelBatchWriterMode lock. More...

bool	shouldConflictWithSecondaryBatchApplication () const

void	setShouldAcquireTicket (bool newValue)
	If set to false, this opts out of the ticket mechanism. More...

bool	shouldAcquireTicket () const

unsigned	numResourcesToUnlockAtEndUnitOfWorkForTest () const
	This function is for unit testing only. More...

Additional Inherited Members
Public Types inherited from mongo::Locker
enum	ClientState { kInactive, kActiveReader, kActiveWriter, kQueuedReader, kQueuedWriter }
	State for reporting the number of active and queued reader and writer clients. More...

Static Public Member Functions inherited from mongo::Locker
static void	setGlobalThrottling (class TicketHolder reading, class TicketHolder writing)
	Require global lock attempts to obtain tickets from 'reading' (for MODE_S and MODE_IS), and from 'writing' (for MODE_IX), which must have static lifetimes. More...

Protected Member Functions inherited from mongo::Locker
	Locker ()

Protected Attributes inherited from mongo::Locker
int	_uninterruptibleLocksRequested = 0
	The number of callers that are guarding from lock interruptions. More...

unsigned	_numResourcesToUnlockAtEndUnitOfWork = 0
	The number of LockRequests to unlock at the end of this WUOW. More...

Constructor & Destructor Documentation

◆ LockerNoop()

mongo::LockerNoop::LockerNoop ( )

inline

Member Function Documentation

◆ beginWriteUnitOfWork()

virtual void mongo::LockerNoop::beginWriteUnitOfWork ( )

inlinevirtual

beginWriteUnitOfWork/endWriteUnitOfWork are called at the start and end of WriteUnitOfWorks.

They can be used to implement two-phase locking. Each call to begin should be matched with an eventual call to end.

endWriteUnitOfWork, if not called in a nested WUOW, will release all two-phase locking held lock resources.

Implements mongo::Locker.

◆ downgrade()

virtual void mongo::LockerNoop::downgrade	(	ResourceId	resId,
		LockMode	newMode
	)

inlinevirtual

Downgrades the specified resource's lock mode without changing the reference count.

Implements mongo::Locker.

◆ downgradeGlobalXtoSForMMAPV1()

virtual void mongo::LockerNoop::downgradeGlobalXtoSForMMAPV1 ( )

inlinevirtual

This is only necessary for the MMAP V1 engine and in particular, the fsyncLock command which needs to first acquire the global lock in X-mode for truncating the journal and then downgrade to S before it blocks.

The downgrade is necessary in order to be nice and not block readers while under fsyncLock.

Implements mongo::Locker.

◆ dump()

virtual void mongo::LockerNoop::dump ( ) const

inlinevirtual

Implements mongo::Locker.

◆ endWriteUnitOfWork()

virtual void mongo::LockerNoop::endWriteUnitOfWork ( )

inlinevirtual

Implements mongo::Locker.

◆ getClientState()

virtual ClientState mongo::LockerNoop::getClientState ( ) const

inlinevirtual

Return whether client is holding any locks (active), or is queued on any locks or waiting for a ticket (throttled).

Implements mongo::Locker.

◆ getId()

virtual LockerId mongo::LockerNoop::getId ( ) const

inlinevirtual

Implements mongo::Locker.

◆ getLockerInfo() [1/2]

virtual void mongo::LockerNoop::getLockerInfo ( LockerInfo * lockerInfo ) const

inlinevirtual

Implements mongo::Locker.

◆ getLockerInfo() [2/2]

virtual boost::optional<LockerInfo> mongo::LockerNoop::getLockerInfo ( ) const

inlinevirtual

Returns boost::none if this is an instance of LockerNoop, or a populated LockerInfo otherwise.

Implements mongo::Locker.

◆ getLockMode()

virtual LockMode mongo::LockerNoop::getLockMode ( ResourceId resId ) const

inlinevirtual

Retrieves the mode in which a lock is held or checks whether the lock held for a particular resource covers the specified mode.

For example isLockHeldForMode will return true for MODE_S, if MODE_X is already held, because MODE_X covers MODE_S.

Implements mongo::Locker.

◆ getThreadId()

stdx::thread::id mongo::LockerNoop::getThreadId ( ) const

inlineoverridevirtual

Get a platform-specific thread identifier of the thread which owns the this locker for tracing purposes.

Implements mongo::Locker.

◆ getWaitingResource()

virtual ResourceId mongo::LockerNoop::getWaitingResource ( ) const

inlinevirtual

Returns the resource that this locker is waiting/blocked on (if any).

If the locker is not waiting for a resource the returned value will be invalid (isValid() == false).

Implements mongo::Locker.

◆ hasLockPending()

virtual bool mongo::LockerNoop::hasLockPending ( ) const

inlinevirtual

Pending means we are currently trying to get a lock (could be the parallel batch writer lock).

Implements mongo::Locker.

◆ hasMaxLockTimeout()

bool mongo::LockerNoop::hasMaxLockTimeout ( )

inlineoverridevirtual

Returns whether this Locker has a maximum lock timeout set.

Implements mongo::Locker.

◆ inAWriteUnitOfWork()

virtual bool mongo::LockerNoop::inAWriteUnitOfWork ( ) const

inlinevirtual

Implements mongo::Locker.

◆ isCollectionLockedForMode()

virtual bool mongo::LockerNoop::isCollectionLockedForMode	(	StringData	ns,
		LockMode	mode
	)		const

inlinevirtual

Implements mongo::Locker.

◆ isDbLockedForMode()

virtual bool mongo::LockerNoop::isDbLockedForMode	(	StringData	dbName,
		LockMode	mode
	)		const

inlinevirtual

Implements mongo::Locker.

◆ isGlobalLockedRecursively()

bool mongo::LockerNoop::isGlobalLockedRecursively ( )

inlineoverridevirtual

Implements mongo::Locker.

◆ isLocked()

virtual bool mongo::LockerNoop::isLocked ( ) const

inlinevirtual

Implements mongo::Locker.

◆ isLockHeldForMode()

virtual bool mongo::LockerNoop::isLockHeldForMode	(	ResourceId	resId,
		LockMode	mode
	)		const

inlinevirtual

Implements mongo::Locker.

◆ isNoop()

virtual bool mongo::LockerNoop::isNoop ( ) const

inlinevirtual

Returns true if this is an instance of LockerNoop.

Because LockerNoop doesn't implement many methods, some users may need to check this first to find out what is safe to call. LockerNoop is only used in unittests and for a brief period at startup, so you can assume you hold the equivalent of a MODE_X lock when using it.

TODO get rid of this once we kill LockerNoop.

Reimplemented from mongo::Locker.

◆ isR()

virtual bool mongo::LockerNoop::isR ( ) const

inlinevirtual

Implements mongo::Locker.

◆ isReadLocked()

virtual bool mongo::LockerNoop::isReadLocked ( ) const

inlinevirtual

Implements mongo::Locker.

◆ isW()

virtual bool mongo::LockerNoop::isW ( ) const

inlinevirtual

Implements mongo::Locker.

◆ isWriteLocked()

virtual bool mongo::LockerNoop::isWriteLocked ( ) const

inlinevirtual

Implements mongo::Locker.

◆ lock() [1/2]

virtual LockResult mongo::LockerNoop::lock	(	OperationContext *	opCtx,
		ResourceId	resId,
		LockMode	mode,
		Date_t	deadline,
		bool	checkDeadlock
	)

inlinevirtual

Acquires lock on the specified resource in the specified mode and returns the outcome of the operation.

See the details for LockResult for more information on what the different results mean.

Each successful acquisition of a lock on a given resource increments the reference count of the lock. Therefore, each call, which returns LOCK_OK must be matched with a corresponding call to unlock.

If setLockTimeoutMillis has been called, then a lock request with a Date_t::max() deadline may throw a LockTimeout error. See setMaxLockTimeout() above for details.

Parameters

opCtx	If provided, will be used to interrupt a LOCK_WAITING state.
resId	Id of the resource to be locked.
mode	Mode in which the resource should be locked. Lock upgrades are allowed.
deadline	How long to wait for the lock to be granted, before returning LOCK_TIMEOUT. This parameter defaults to an infinite deadline. If Milliseconds(0) is passed, the request will return immediately, if the request could not be granted right away.
checkDeadlock	Whether to enable deadlock detection for this acquisition. This parameter is put in place until we can handle deadlocks at all places, which acquire locks.

Returns: All LockResults except for LOCK_WAITING, because it blocks.

Implements mongo::Locker.

◆ lock() [2/2]

virtual LockResult mongo::LockerNoop::lock	(	ResourceId	resId,
		LockMode	mode,
		Date_t	deadline,
		bool	checkDeadlock
	)

inlinevirtual

Calling lock without an OperationContext does not allow LOCK_WAITING states to be interrupted.

Implements mongo::Locker.

◆ lockGlobal() [1/2]

virtual LockResult mongo::LockerNoop::lockGlobal	(	OperationContext *	opCtx,
		LockMode	mode
	)

inlinevirtual

This should be the first method invoked for a particular Locker object.

It acquires the Global lock in the specified mode and effectively indicates the mode of the operation. This is what the lock modes on the global lock mean:

IX - Regular write operation IS - Regular read operation S - Stops all write activity. Used for administrative operations (repl, etc). X - Stops all activity. Used for administrative operations (repl state changes, shutdown, etc).

This method can be called recursively, but each call to lockGlobal must be accompanied by a call to unlockGlobal.

Parameters

opCtx	OperationContext used to interrupt the lock waiting, if provided.
mode	Mode in which the global lock should be acquired. Also indicates the intent of the operation.

Returns: LOCK_OK, if the global lock (and the flush lock, for the MMAP V1 engine) were acquired within the specified time bound. Otherwise, the respective failure code and neither lock will be acquired.

Implements mongo::Locker.

◆ lockGlobal() [2/2]

virtual LockResult mongo::LockerNoop::lockGlobal ( LockMode mode )

inlinevirtual

Implements mongo::Locker.

◆ lockGlobalBegin() [1/2]

virtual LockResult mongo::LockerNoop::lockGlobalBegin	(	OperationContext *	opCtx,
		LockMode	mode,
		Date_t	deadline
	)

inlinevirtual

Requests the global lock to be acquired in the specified mode.

See the comments for lockBegin/Complete for more information on the semantics. The deadline indicates the absolute time point when this lock acquisition will time out, if not yet granted. The lockGlobalBegin method has a deadline for use with the TicketHolder, if there is one.

Implements mongo::Locker.

◆ lockGlobalBegin() [2/2]

virtual LockResult mongo::LockerNoop::lockGlobalBegin	(	LockMode	mode,
		Date_t	deadline
	)

inlinevirtual

Implements mongo::Locker.

◆ lockGlobalComplete() [1/2]

virtual LockResult mongo::LockerNoop::lockGlobalComplete	(	OperationContext *	opCtx,
		Date_t	deadline
	)

inlinevirtual

Calling lockGlobalComplete without an OperationContext does not allow the lock acquisition to be interrupted.

Implements mongo::Locker.

◆ lockGlobalComplete() [2/2]

virtual LockResult mongo::LockerNoop::lockGlobalComplete ( Date_t deadline )

inlinevirtual

Implements mongo::Locker.

◆ lockMMAPV1Flush()

virtual void mongo::LockerNoop::lockMMAPV1Flush ( )

inlinevirtual

This method is used only in the MMAP V1 storage engine, otherwise it is a no-op.

See the comments in the implementation for more details on how MMAP V1 journaling works.

Implements mongo::Locker.

◆ reacquireTicket()

virtual void mongo::LockerNoop::reacquireTicket ( OperationContext * opCtx )

inlinevirtual

Reacquires a ticket for the Locker.

This must only be called after releaseTicket(). It restores the ticket under its previous LockMode. An OperationContext is required to interrupt the ticket acquisition to prevent deadlocks. A dead lock is possible when a ticket is reacquired while holding a lock.

Implements mongo::Locker.

◆ releaseTicket()

virtual void mongo::LockerNoop::releaseTicket ( )

inlinevirtual

Releases the ticket associated with the Locker.

This allows locks to be held without contributing to reader/writer throttling.

Implements mongo::Locker.

◆ restoreLockState() [1/2]

virtual void mongo::LockerNoop::restoreLockState	(	OperationContext *	opCtx,
		const LockSnapshot &	stateToRestore
	)

inlinevirtual

Re-locks all locks whose state was stored in 'stateToRestore'.

Parameters

opCtx An operation context that enables the restoration to be interrupted.

Implements mongo::Locker.

◆ restoreLockState() [2/2]

virtual void mongo::LockerNoop::restoreLockState ( const LockSnapshot & stateToRestore )

inlinevirtual

Implements mongo::Locker.

◆ saveLockStateAndUnlock()

virtual bool mongo::LockerNoop::saveLockStateAndUnlock ( LockSnapshot * stateOut )

inlinevirtual

Retrieves all locks held by this transaction, other than RESOURCE_MUTEX locks, and what mode they're held in.

Stores these locks in 'stateOut', destroying any previous state. Unlocks all locks held by this transaction. This functionality is used for yielding, which is voluntary/cooperative lock release and reacquisition in order to allow for interleaving of otherwise conflicting long-running operations.

This functionality is also used for releasing locks on databases and collections when cursors are dormant and waiting for a getMore request.

Returns true if locks are released. It is expected that restoreLockerImpl will be called in the future.

Returns false if locks are not released. restoreLockState(...) does not need to be called in this case.

Implements mongo::Locker.

◆ setMaxLockTimeout()

void mongo::LockerNoop::setMaxLockTimeout ( Milliseconds maxTimeout )

inlineoverridevirtual

This is useful to ensure that potential deadlocks do not occur.

Overrides provided timeouts in lock requests with 'maxTimeout' if the provided timeout is greater. Basically, no lock acquisition will take longer than 'maxTimeout'.

If an UninterruptibleLockGuard is set during a lock request, the max timeout override will be ignored.

Future lock requests may throw LockTimeout errors if a lock request provides a Date_t::max() deadline and 'maxTimeout' is reached. Presumably these callers do not expect to handle lock acquisition failure, so this is done to ensure the caller does not proceed as if the lock were successfully acquired.

Implements mongo::Locker.

◆ setSharedLocksShouldTwoPhaseLock()

void mongo::LockerNoop::setSharedLocksShouldTwoPhaseLock ( bool sharedLocksShouldTwoPhaseLock )

inlineoverridevirtual

Indicate that shared locks should participate in two-phase locking for this Locker instance.

Implements mongo::Locker.

◆ unlock()

virtual bool mongo::LockerNoop::unlock ( ResourceId resId )

inlinevirtual

Releases a lock previously acquired through a lock call.

It is an error to try to release lock which has not been previously acquired (invariant violation).

Returns: true if the lock was actually released; false if only the reference count was decremented, but the lock is still held.

Implements mongo::Locker.

◆ unlockGlobal()

virtual bool mongo::LockerNoop::unlockGlobal ( )

inlinevirtual

Decrements the reference count on the global lock.

If the reference count on the global lock hits zero, the transaction is over, and unlockGlobal unlocks all other locks except for RESOURCE_MUTEX locks.

Returns: true if this is the last endTransaction call (i.e., the global lock was released); false if there are still references on the global lock. This value should not be relied on and is only used for assertion purposes.; false if the global lock is still held.

Implements mongo::Locker.

◆ unsetMaxLockTimeout()

void mongo::LockerNoop::unsetMaxLockTimeout ( )

inlineoverridevirtual

Clears the max lock timeout override set by setMaxLockTimeout() above.

Implements mongo::Locker.

◆ unsetThreadId()

void mongo::LockerNoop::unsetThreadId ( )

inlineoverridevirtual

Clears any cached thread id values.

Implements mongo::Locker.

◆ updateThreadIdToCurrentThread()

void mongo::LockerNoop::updateThreadIdToCurrentThread ( )

inlineoverridevirtual

Updates any cached thread id values to represent the current thread.

Implements mongo::Locker.

The documentation for this class was generated from the following file:

/home/louis/git/mongodbsource.github.io/src/src/mongo/db/concurrency/locker_noop.h

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ LockerNoop()

Member Function Documentation

◆ beginWriteUnitOfWork()

◆ downgrade()

◆ downgradeGlobalXtoSForMMAPV1()

◆ dump()

◆ endWriteUnitOfWork()

◆ getClientState()

◆ getId()

◆ getLockerInfo() [1/2]

◆ getLockerInfo() [2/2]

◆ getLockMode()

◆ getThreadId()

◆ getWaitingResource()

◆ hasLockPending()

◆ hasMaxLockTimeout()

◆ inAWriteUnitOfWork()

◆ isCollectionLockedForMode()

◆ isDbLockedForMode()

◆ isGlobalLockedRecursively()

◆ isLocked()

◆ isLockHeldForMode()

◆ isNoop()

◆ isR()

◆ isReadLocked()

◆ isW()

◆ isWriteLocked()

◆ lock() [1/2]

◆ lock() [2/2]

◆ lockGlobal() [1/2]

◆ lockGlobal() [2/2]

◆ lockGlobalBegin() [1/2]

◆ lockGlobalBegin() [2/2]

◆ lockGlobalComplete() [1/2]

◆ lockGlobalComplete() [2/2]

◆ lockMMAPV1Flush()

◆ reacquireTicket()

◆ releaseTicket()

◆ restoreLockState() [1/2]

◆ restoreLockState() [2/2]

◆ saveLockStateAndUnlock()

◆ setMaxLockTimeout()

◆ setSharedLocksShouldTwoPhaseLock()

◆ unlock()

◆ unlockGlobal()

◆ unsetMaxLockTimeout()

◆ unsetThreadId()

◆ updateThreadIdToCurrentThread()