CNum::DataStructs::HazardPointer Namespace Reference

Tools for protecting "hazerdous" objects in memory. More...

Classes
struct	HazardSlot
	A slot in which to store a protected pointer. More...
struct	Retire
	A retired protected pointer. More...
class	HazardPtrDomain
	The domain of all hazard pointers. More...
class	HazardPtrGuard
	Thread local guards for hazard pointers. More...

Functions
template<typename T>
void	default_hazard_ptr_delete (void *ptr)
	Default delete function for pointers.
template<typename T>
T *	protect (::std::atomic< T * > &src, HazardSlot *slot)
	Protect an atomic pointer.
template<typename T>
void	protect (T *src, HazardSlot *slot)
	Protect a raw pointer.
template<typename T>
void	retire (T *ptr)
	Retire a pointer.
void	scan ()
	Free memory of objects pointed to by pointers that are no longer hazardous.
void	flush ()
	Force a scan.

Variables
constexpr size_t	MAX_HP_SLOTS = 1024
	The maximum amount of hazard pointer slots (globally) Add more as needed.
constexpr size_t	SLOTS_PER_THREAD = 2
	The amount of slots 1 thread can have.
constexpr size_t	RETIRED_SCAN_THRESHOLD = 64
	The threshold of Retire objects in the tls_retire at which we call scan().
thread_local ::std::vector< Retire >	tls_retire
	The thread local storage of retired objects.

Detailed Description

Tools for protecting "hazerdous" objects in memory.

Function Documentation

default_hazard_ptr_delete()

template<typename T>

void CNum::DataStructs::HazardPointer::default_hazard_ptr_delete

(

void *

ptr

)

Default delete function for pointers.

Parameters

ptr	The pointer to free

flush()

void CNum::DataStructs::HazardPointer::flush

(

)

Force a scan.

protect() [1/2]

template<typename T>

T * CNum::DataStructs::HazardPointer::protect	(	::std::atomic< T * > &	src,
		HazardSlot *	slot )

Protect an atomic pointer.

Used for ensuring that a pointer shared by multiple threads does not get deleted (freed) when another is actively using it

Parameters

src	Atomic pointer to protect
slot	The slot in which to store the pointer

Returns

The raw pointer

protect() [2/2]

template<typename T>

void CNum::DataStructs::HazardPointer::protect	(	T *	src,
		HazardSlot *	slot )

Protect a raw pointer.

Used for ensuring that a pointer shared by multiple threads does not get deleted (freed) when another is actively using it

Parameters

src	The raw pointer to protect
slot	The slot in which to store the pointer

retire()

template<typename T>

void CNum::DataStructs::HazardPointer::retire

(

T *

ptr

)

Retire a pointer.

Mark protected pointer as ready to free

Parameters

ptr	The raw pointer to free

scan()

void CNum::DataStructs::HazardPointer::scan

(

)

Free memory of objects pointed to by pointers that are no longer hazardous.

Iterate over the tls_retire and check if the pointers are hazardous by checking if it is active in the global domain (i.e. marked hazardous by thread)

Variable Documentation

MAX_HP_SLOTS

size_t CNum::DataStructs::HazardPointer::MAX_HP_SLOTS = 1024

constexpr

The maximum amount of hazard pointer slots (globally) Add more as needed.

RETIRED_SCAN_THRESHOLD

size_t CNum::DataStructs::HazardPointer::RETIRED_SCAN_THRESHOLD = 64

constexpr

The threshold of Retire objects in the tls_retire at which we call scan().

SLOTS_PER_THREAD

size_t CNum::DataStructs::HazardPointer::SLOTS_PER_THREAD = 2

constexpr

The amount of slots 1 thread can have.

I assigned a value of 2 because 2 is all that is required for my lock-free concurrent queue. But for your own implementations of lock-free data structures you may need to increase this value.

tls_retire

thread_local ::std::vector<Retire> CNum::DataStructs::HazardPointer::tls_retire

inline

The thread local storage of retired objects.