Reference counting

Reference counting. More...

Data Structures
struct	ref_t
	Reference counting structure. More...

Macros
#define	REF_MAGIC   0x26CB6E4C
	Magic value used in debug builds to check for corruption or invalid use of the ref_t structure.
#define	DEREF_DEFER(ptr)   __attribute__((cleanup(ref_defer_cleanup))) void* CONCAT(p, __COUNTER__) = (ptr)
	RAII-style cleanup for scoped references.
#define	REF(ptr)
	Increment reference count.
#define	DEREF(ptr)
	Decrement reference count.

Functions
static void	ref_init (ref_t *ref, void *free)
	Initialize a reference counter.
static void *	ref_inc (void *ptr)
	Increment reference count.
static void	ref_dec (void *ptr)
	Decrement reference count.
static void	ref_defer_cleanup (void **ptr)

Detailed Description

Reference counting.

Macro Definition Documentation

DEREF

#define DEREF

(

ptr

)

Value:

    ({ \
        ref_t* ref = (ref_t*)ptr; \
        ref_dec(ref); \
    })

Decrement reference count.

Atomically decrements the reference counter. Used to avoid the need for a typecast. The magic number checking makes sure we cant accidentally misuse this.

Parameters

ptr	Pointer to the struct containing ref_t as its first member, can be NULL.

Definition at line 80 of file ref.h.

DEREF_DEFER

#define DEREF_DEFER

(

ptr

)

__attribute__((cleanup(ref_defer_cleanup))) void* CONCAT(p, __COUNTER__) = (ptr)

RAII-style cleanup for scoped references.

Uses GCC's cleanup attribute to automatically call ref_dec when going out of scope.

Parameters

ptr	Pointer to the struct containing ref_t as its first member, can be NULL.

Definition at line 54 of file ref.h.

REF

#define REF

(

ptr

)

Value:

    ({ \
        ref_t* ref = (ref_t*)ptr; \
        ref_inc(ref); \
        ptr; \
    })

Increment reference count.

Atomically increments the reference counter. Used to avoid the need for a typecast. The magic number checking makes sure we cant accidentally misuse this.

Parameters

ptr	Pointer to the struct containing ref_t as its first member, can be NULL.

Returns

The ptr passed as input

Definition at line 65 of file ref.h.

REF_MAGIC

#define REF_MAGIC   0x26CB6E4C

Magic value used in debug builds to check for corruption or invalid use of the ref_t structure.

Definition at line 19 of file ref.h.

Function Documentation

ref_dec()

static void ref_dec ( void *  ptr )

inlinestatic

Decrement reference count.

If count reaches zero it calls the registered cleanup function.

Parameters

ptr	Pointer to the struct containing ref_t as its first member, can be NULL.

Definition at line 127 of file ref.h.

References assert, atomic_fetch_sub_explicit, atomic_thread_fence, ref_t::count, count, ref_t::free, ref_t::magic, memory_order_acquire, memory_order_relaxed, NULL, and REF_MAGIC.

Referenced by init_process_spawn(), and ref_defer_cleanup().

ref_defer_cleanup()

static void ref_defer_cleanup ( void **  ptr )

inlinestatic

Definition at line 155 of file ref.h.

References ref_dec().

ref_inc()

static void * ref_inc ( void *  ptr )

inlinestatic

Increment reference count.

Parameters

ptr	Pointer to the struct containing ref_t as its first member, can be NULL.

Returns

The ptr passed as input

Definition at line 107 of file ref.h.

References assert, atomic_fetch_add_explicit, ref_t::count, ref_t::magic, memory_order_relaxed, NULL, and REF_MAGIC.

ref_init()

static void ref_init ( ref_t *  ref, void *  free  )

inlinestatic

Initialize a reference counter.

Parameters

ref	Pointer to the reference counter structure
free	Cleanup function to call when count reaches zero

Definition at line 92 of file ref.h.

References atomic_init, ref_t::count, free(), ref_t::free, ref_t::magic, and REF_MAGIC.

Referenced by aml_object_new(), dentry_new(), file_new(), inode_new(), local_conn_new(), local_listen_new(), mount_new(), process_init(), shmem_object_new(), socket_new(), and superblock_new().