Entry point for the lock manager scheduling functionality. More...

#include <lock_manager.h>

Detailed Description

Entry point for the lock manager scheduling functionality.

Don't use it directly, but instead go through the Locker interface.

Classes
struct	LockBucket

struct	Partition

Public Member Functions
	LockManager ()

	~LockManager ()

LockResult	lock (ResourceId resId, LockRequest *request, LockMode mode)
	Acquires lock on the specified resource in the specified mode and returns the outcome of the operation. More...

LockResult	convert (ResourceId resId, LockRequest *request, LockMode newMode)

bool	unlock (LockRequest *request)
	Decrements the reference count of a previously locked request and if the reference count becomes zero, removes the request and proceeds to granting any conflicts. More...

void	downgrade (LockRequest *request, LockMode newMode)
	Downgrades the mode in which an already granted request is held, without changing the reference count of the lock request. More...

void	cleanupUnusedLocks ()
	Iterates through all buckets and deletes all locks, which have no requests on them. More...

void	dump () const
	Dumps the contents of all locks to the log. More...

void	getLockInfoBSON (const std::map< LockerId, BSONObj > &lockToClientMap, BSONObjBuilder *result)
	Dumps the contents of all locks into a BSON object to be used in lockInfo command in the shell. More...

Private Member Functions
	MONGO_DISALLOW_COPYING (LockManager)

LockBucket *	_getBucket (ResourceId resId) const
	Retrieves the bucket in which the particular resource must reside. More...

Partition *	_getPartition (LockRequest *request) const
	Retrieves the Partition that a particular LockRequest should use for intent locking. More...

void	_dumpBucket (const LockBucket *bucket) const
	Prints the contents of a bucket to the log. More...

void	_dumpBucketToBSON (const std::map< LockerId, BSONObj > &lockToClientMap, const LockBucket bucket, BSONObjBuilder result)
	Dump the contents of a bucket to the BSON. More...

void	_buildBucketBSON (const LockRequest iter, const std::map< LockerId, BSONObj > &lockToClientMap, const LockBucket bucket, BSONArrayBuilder *locks)
	Build the BSON object containing the lock info for a particular bucket. More...

void	_onLockModeChanged (LockHead *lock, bool checkConflictQueue)
	Should be invoked when the state of a lock changes in a way, which could potentially allow other blocked requests to proceed. More...

void	_cleanupUnusedLocksInBucket (LockBucket *bucket)
	Helper function to delete all locks that have no request on them on a single bucket. More...

Private Attributes
LockBucket *	_lockBuckets

Partition *	_partitions

Static Private Attributes
static const unsigned	_numLockBuckets

static const unsigned	_numPartitions = 32

Friends
class	DeadlockDetector

struct	LockHead

Constructor & Destructor Documentation

◆ LockManager()

mongo::LockManager::LockManager ( )

◆ ~LockManager()

mongo::LockManager::~LockManager ( )

Member Function Documentation

◆ _buildBucketBSON()

void mongo::LockManager::_buildBucketBSON	(	const LockRequest *	iter,
		const std::map< LockerId, BSONObj > &	lockToClientMap,
		const LockBucket *	bucket,
		BSONArrayBuilder *	locks
	)

private

Build the BSON object containing the lock info for a particular bucket.

The lockToClientMap is used to map the lockerId to more useful client information.

◆ _cleanupUnusedLocksInBucket()

void mongo::LockManager::_cleanupUnusedLocksInBucket ( LockBucket * bucket )

private

Helper function to delete all locks that have no request on them on a single bucket.

Called by cleanupUnusedLocks()

◆ _dumpBucket()

void mongo::LockManager::_dumpBucket ( const LockBucket * bucket ) const

private

Prints the contents of a bucket to the log.

◆ _dumpBucketToBSON()

void mongo::LockManager::_dumpBucketToBSON	(	const std::map< LockerId, BSONObj > &	lockToClientMap,
		const LockBucket *	bucket,
		BSONObjBuilder *	result
	)

private

Dump the contents of a bucket to the BSON.

◆ _getBucket()

LockManager::LockBucket * mongo::LockManager::_getBucket ( ResourceId resId ) const

private

Retrieves the bucket in which the particular resource must reside.

There is no need to hold a lock when calling this function.

◆ _getPartition()

LockManager::Partition * mongo::LockManager::_getPartition ( LockRequest * request ) const

private

Retrieves the Partition that a particular LockRequest should use for intent locking.

◆ _onLockModeChanged()

void mongo::LockManager::_onLockModeChanged	(	LockHead *	lock,
		bool	checkConflictQueue
	)

private

Should be invoked when the state of a lock changes in a way, which could potentially allow other blocked requests to proceed.

MUST be called under the lock bucket's mutex.

Parameters

lock	Lock whose grant state should be recalculated.
checkConflictQueue	Whether to go through the conflict queue. This is an optimisation in that we only need to check the conflict queue if one of the granted modes, which was conflicting before became zero.

◆ cleanupUnusedLocks()

void mongo::LockManager::cleanupUnusedLocks ( )

Iterates through all buckets and deletes all locks, which have no requests on them.

This call is kind of expensive and should only be used for reducing the memory footprint of the lock manager.

◆ convert()

LockResult mongo::LockManager::convert	(	ResourceId	resId,
		LockRequest *	request,
		LockMode	newMode
	)

◆ downgrade()

void mongo::LockManager::downgrade	(	LockRequest *	request,
		LockMode	newMode
	)

Downgrades the mode in which an already granted request is held, without changing the reference count of the lock request.

This call never blocks, will always succeed and may potentially allow other blocked lock requests to proceed.

Parameters

request	Request, already in granted mode through a previous call to lock.
newMode	Mode, which is less-restrictive than the mode in which the request is already held. I.e., the conflict set of newMode must be a sub-set of the conflict set of the request's current mode.

◆ dump()

void mongo::LockManager::dump ( ) const

Dumps the contents of all locks to the log.

◆ getLockInfoBSON()

void mongo::LockManager::getLockInfoBSON	(	const std::map< LockerId, BSONObj > &	lockToClientMap,
		BSONObjBuilder *	result
	)

Dumps the contents of all locks into a BSON object to be used in lockInfo command in the shell.

◆ lock()

LockResult mongo::LockManager::lock	(	ResourceId	resId,
		LockRequest *	request,
		LockMode	mode
	)

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.

Locking the same resource twice increments the reference count of the lock so each call to lock must be matched with a call to unlock with the same resource.

Parameters

resId	Id of the resource to be locked.
request	LockRequest structure on which the state of the request will be tracked. This value cannot be NULL and the notify value must be set. If the return value is not LOCK_WAITING, this pointer can be freed and will not be used any more.

If the return value is LOCK_WAITING, the notification method will be called at some point into the future, when the lock either becomes granted or a deadlock is discovered. If unlock is called before the lock becomes granted, the notification will not be invoked.

If the return value is LOCK_WAITING, the notification object must live at least until the notify method has been invoked or unlock has been called for the resource it was assigned to. Failure to do so will cause the lock manager to call into an invalid memory location.

Parameters

mode	Mode in which the resource should be locked. Lock upgrades are allowed.

Returns: See comments for LockResult.

◆ MONGO_DISALLOW_COPYING()

mongo::LockManager::MONGO_DISALLOW_COPYING ( LockManager )

private

◆ unlock()

bool mongo::LockManager::unlock ( LockRequest * request )

Decrements the reference count of a previously locked request and if the reference count becomes zero, removes the request and proceeds to granting any conflicts.

This method always succeeds and never blocks.

Parameters

request A previously locked request. Calling unlock more times than lock was called for the same LockRequest is an error.

Returns: true if this is the last reference for the request; false otherwise

Friends And Related Function Documentation

◆ DeadlockDetector

friend class DeadlockDetector

friend

◆ LockHead

friend struct LockHead

friend

Member Data Documentation

◆ _lockBuckets

LockBucket* mongo::LockManager::_lockBuckets

private

◆ _numLockBuckets

const unsigned mongo::LockManager::_numLockBuckets

staticprivate

◆ _numPartitions

const unsigned mongo::LockManager::_numPartitions = 32

staticprivate

◆ _partitions

Partition* mongo::LockManager::_partitions

private

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

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

Detailed Description

Classes

Public Member Functions

Private Member Functions

Private Attributes

Static Private Attributes

Friends

Constructor & Destructor Documentation

◆ LockManager()

◆ ~LockManager()

Member Function Documentation

◆ _buildBucketBSON()

◆ _cleanupUnusedLocksInBucket()

◆ _dumpBucket()

◆ _dumpBucketToBSON()

◆ _getBucket()

◆ _getPartition()

◆ _onLockModeChanged()

◆ cleanupUnusedLocks()

◆ convert()

◆ downgrade()

◆ dump()

◆ getLockInfoBSON()

◆ lock()

◆ MONGO_DISALLOW_COPYING()

◆ unlock()

Friends And Related Function Documentation

◆ DeadlockDetector

◆ LockHead

Member Data Documentation

◆ _lockBuckets

◆ _numLockBuckets

◆ _numPartitions

◆ _partitions