mongo::DeadlockDetector Class Reference

Iteratively builds the wait-for graph, starting from a given blocked Locker and stops either when all reachable nodes have been checked or if a cycle is detected. More...

#include <lock_manager.h>

Detailed Description

Iteratively builds the wait-for graph, starting from a given blocked Locker and stops either when all reachable nodes have been checked or if a cycle is detected.

This class is thread-safe. Because locks may come and go in parallel with deadlock detection, it may report false positives, but if there is a stable cycle it will be discovered.

Implemented as a separate class in order to facilitate diagnostics and also unit-testing for cases where locks come and go in parallel with deadlock detection.

Classes
struct	Edges
struct	UnprocessedNode

Public Member Functions
	DeadlockDetector (const LockManager &lockMgr, const Locker *initialLocker)
	Initializes the wait-for graph builder with the LM to operate on and a locker object from which to start the search. More...
DeadlockDetector &	check ()
bool	next ()
	Processes the next wait for node and queues up its set of owners to the unprocessed queue. More...
bool	hasCycle () const
	Checks whether a cycle exists in the wait-for graph, which has been built so far. More...
std::string	toString () const
	Produces a string containing the wait-for graph that has been built so far. More...

Private Types
typedef std::vector< LockerId >	ConflictingOwnersList
typedef std::map< LockerId, Edges >	WaitForGraph
typedef WaitForGraph::value_type	WaitForGraphPair
typedef std::deque< UnprocessedNode >	UnprocessedNodesQueue

Private Member Functions
void	_processNextNode (const UnprocessedNode &node)

Private Attributes
const LockManager &	_lockMgr
const LockerId	_initialLockerId
UnprocessedNodesQueue	_queue
WaitForGraph	_graph
bool	_foundCycle

Member Typedef Documentation

ConflictingOwnersList

typedef std::vector<LockerId> mongo::DeadlockDetector::ConflictingOwnersList

private

UnprocessedNodesQueue

typedef std::deque<UnprocessedNode> mongo::DeadlockDetector::UnprocessedNodesQueue

private

WaitForGraph

typedef std::map<LockerId, Edges> mongo::DeadlockDetector::WaitForGraph

private

WaitForGraphPair

typedef WaitForGraph::value_type mongo::DeadlockDetector::WaitForGraphPair

private

Constructor & Destructor Documentation

DeadlockDetector()

mongo::DeadlockDetector::DeadlockDetector	(	const LockManager &	lockMgr,
		const Locker *	initialLocker
	)

Initializes the wait-for graph builder with the LM to operate on and a locker object from which to start the search.

Deadlock will only be reported if there is a wait cycle in which the initial locker participates.

Member Function Documentation

_processNextNode()

void mongo::DeadlockDetector::_processNextNode ( const UnprocessedNode &  node )

private

check()

DeadlockDetector& mongo::DeadlockDetector::check ( )

inline

hasCycle()

bool mongo::DeadlockDetector::hasCycle

(

)

const

Checks whether a cycle exists in the wait-for graph, which has been built so far.

It's only useful to call this after next() has returned false.

next()

bool mongo::DeadlockDetector::next

(

)

Processes the next wait for node and queues up its set of owners to the unprocessed queue.

Returns

true if there are more unprocessed nodes and no cycle has been discovered yet; false if either all reachable nodes have been processed or

toString()

std::string mongo::DeadlockDetector::toString

(

)

const

Produces a string containing the wait-for graph that has been built so far.

Member Data Documentation

_foundCycle

bool mongo::DeadlockDetector::_foundCycle

private

_graph

WaitForGraph mongo::DeadlockDetector::_graph

private

_initialLockerId

const LockerId mongo::DeadlockDetector::_initialLockerId

private

_lockMgr

const LockManager& mongo::DeadlockDetector::_lockMgr

private

_queue

UnprocessedNodesQueue mongo::DeadlockDetector::_queue

private

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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