Add function _init_once for intrusive shared pointer
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Patrick Pelissier committed
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@@ -4019,12 +4019,22 @@ TODO: Document shared resource
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This header is for creating intrusive shared pointer.
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#### ISHARED\_INTERFACE(name, type)
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#### ISHARED\_PTR\_INTERFACE(name, type)
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Extend the definition of the structure of an object of type 'type' by adding the
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necessary interface to handle it as a shared pointer named 'name'.
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It shall be put within the structure definition of the object (See example).
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#### ISHARED\_PTR\_STATIC\_INIT(name, type)
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Provide the static initialization value of an object defined with a
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ISHARED\_PTR\_INTERFACE extra fields. It shall be used only for global
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variables with the \_init\_once function.
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Usage:
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struct mystruct variable = { ISHARED_PTR_STATIC_INIT(ishared_double, struct mystruct) };
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#### ISHARED\_PTR\_DEF(name, type[, oplist])
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Define the associated methods to handle the shared pointer named 'name'
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@@ -4060,6 +4070,7 @@ so that the CLEAR method doesn't try to free the objectslike this:
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(NEW(0), DEL(0))
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NEW & DEL operators shall be either both defined, or both disabled.
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Example (dynamic):
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@@ -4116,12 +4127,23 @@ This function is thread safe.
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Allocate a new object, initialize it and return an initialized shared pointer to it.
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The used allocation function is the ALLOC operator.
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In this case, it is assumed that the DEL operator has not been disabled.
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The used allocation function is the NEW operator.
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This function is created only if the INIT method is defined in the oplist
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and if the NEW method has not been disabled in the oplist.
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##### name\_t name\_init\_once(type *object)
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Initialize the new object 'object' and return an initialized shared pointer to it.
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The INIT operator of 'object' is ensured to be called only once,
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even if multiple threads try to initialize it at the same time.
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Once the object is fully cleared, the initialization function may occur once again.
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object shall be a global variable initialized with the ISHARED_PTR_STATIC_INIT macro.
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This function is created only if the INIT method is defined in the oplist
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and if the NEW method has been disabled in the oplist.
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##### void name\_clear(name\_t shared)
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Clear the shared pointer, releasing ownership of the object
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+44
-7
@@ -46,6 +46,11 @@ M_BEGIN_PROTECTED_CODE
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atomic_int M_C(name, _cpt)
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/* Value of the interface field for static intialization. */
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#define ISHARED_PTR_STATIC_INIT(name, type) \
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.M_C(name, _cpt) = ATOMIC_VAR_INIT(0)
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/* Define the intrusive shared pointer type and its static inline functions.
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USAGE: ISHARED_PTR_DEF(name, type, [, oplist]) */
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#define ISHARED_PTR_DEF(name, ...) \
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@@ -122,7 +127,7 @@ M_BEGIN_PROTECTED_CODE
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{ \
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/* Initialize the type referenced by the pointer */ \
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if (M_LIKELY (ptr != NULL)) { \
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atomic_init(&ptr->M_C(name, _cpt), 1); \
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atomic_init(&ptr->M_C(name, _cpt), 2); \
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} \
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return ptr; \
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} \
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@@ -131,7 +136,7 @@ M_BEGIN_PROTECTED_CODE
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M_C(name, _init_set)(shared_t shared) \
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{ \
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if (M_LIKELY (shared != NULL)) { \
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int n = atomic_fetch_add(&(shared->M_C(name, _cpt)), 1); \
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int n = atomic_fetch_add(&(shared->M_C(name, _cpt)), 2); \
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(void) n; \
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} \
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return shared; \
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@@ -144,9 +149,41 @@ M_BEGIN_PROTECTED_CODE
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*ptr = M_C(name, _init_set)(shared); \
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} \
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\
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M_IF_METHOD(INIT, oplist)( \
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M_IF_DISABLED_METHOD(NEW, oplist) \
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( /* Nothing to do */, M_IF_METHOD(INIT, oplist) \
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( \
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( \
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/* This function is only for static object */ \
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static inline shared_t \
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M_C(name, _init_once)(type *shared) \
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{ \
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if (M_LIKELY (shared != NULL)) { \
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/* Pretty much like atomic_add, except the first one increment by 1, others by 2 */ \
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int o = atomic_load(&(shared->M_C(name, _cpt))); \
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int n; \
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do { \
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n = o + 1 + (o != 0); \
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} while (!atomic_compare_exchange_strong(&(shared->M_C(name, _cpt)), &o, n)); \
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if (o == 0) { \
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/* Partial initialization: _cpt is odd */ \
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/* Call the INIT function once */ \
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M_CALL_INIT(oplist, *shared); \
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/* Finish initialization: _cpt is even */ \
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atomic_fetch_add(&(shared->M_C(name, _cpt)), 1); \
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} else if ( (o&1) != 0) { \
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/* Not fully initialized yet: wait for initialization */ \
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m_core_backoff_ct bkoff; \
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m_core_backoff_init(bkoff); \
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/* Wait for _cpt to be _even */ \
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while ((atomic_load(&(shared->M_C(name, _cpt)))&1) != 0 ) { \
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m_core_backoff_wait(bkoff); \
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} \
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} \
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M_ASSERT( (atomic_load(&(shared->M_C(name, _cpt)))&1) == 0); \
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} \
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return shared; \
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} \
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, \
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/* This function is only for dynamic object */ \
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static inline shared_t \
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M_C(name, _init_new)(void) \
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{ \
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@@ -156,17 +193,17 @@ M_BEGIN_PROTECTED_CODE
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return NULL; \
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} \
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M_CALL_INIT(oplist, *ptr); \
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atomic_init (&ptr->M_C(name, _cpt), 1); \
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atomic_init (&ptr->M_C(name, _cpt), 2); \
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return ptr; \
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} \
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, /* End of INIT */) \
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/* End of NEW */) \
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, /* End of INIT */) \
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\
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static inline void \
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M_C(name, _clear)(shared_t shared) \
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{ \
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if (shared != NULL) { \
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if (atomic_fetch_sub(&(shared->M_C(name, _cpt)), 1) == 1) { \
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if (atomic_fetch_sub(&(shared->M_C(name, _cpt)), 2) == 2) { \
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M_CALL_CLEAR(oplist, *shared); \
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M_IF_DISABLED_METHOD(DEL, oplist)(, M_CALL_DEL(oplist, shared);) \
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} \
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