diff options
Diffstat (limited to 'contrib/tools/python3/Modules/gcmodule.c')
| -rw-r--r-- | contrib/tools/python3/Modules/gcmodule.c | 2176 |
1 files changed, 133 insertions, 2043 deletions
diff --git a/contrib/tools/python3/Modules/gcmodule.c b/contrib/tools/python3/Modules/gcmodule.c index 39856b8eb70..ee24900ae88 100644 --- a/contrib/tools/python3/Modules/gcmodule.c +++ b/contrib/tools/python3/Modules/gcmodule.c @@ -1,135 +1,16 @@ /* - - Reference Cycle Garbage Collection - ================================== - - Neil Schemenauer <[email protected]> - - Based on a post on the python-dev list. Ideas from Guido van Rossum, - Eric Tiedemann, and various others. - - http://www.arctrix.com/nas/python/gc/ - - The following mailing list threads provide a historical perspective on - the design of this module. Note that a fair amount of refinement has - occurred since those discussions. - - http://mail.python.org/pipermail/python-dev/2000-March/002385.html - http://mail.python.org/pipermail/python-dev/2000-March/002434.html - http://mail.python.org/pipermail/python-dev/2000-March/002497.html - - For a highlevel view of the collection process, read the collect - function. - -*/ + * Python interface to the garbage collector. + * + * See Python/gc.c for the implementation of the garbage collector. + */ #include "Python.h" -#include "pycore_context.h" -#include "pycore_initconfig.h" -#include "pycore_interp.h" // PyInterpreterState.gc -#include "pycore_object.h" -#include "pycore_pyerrors.h" -#include "pycore_pystate.h" // _PyThreadState_GET() -#include "pydtrace.h" +#include "pycore_gc.h" +#include "pycore_object.h" // _PyObject_IS_GC() +#include "pycore_pystate.h" // _PyInterpreterState_GET() typedef struct _gc_runtime_state GCState; -/*[clinic input] -module gc -[clinic start generated code]*/ -/*[clinic end generated code: output=da39a3ee5e6b4b0d input=b5c9690ecc842d79]*/ - - -#ifdef Py_DEBUG -# ifndef GC_NDEBUG -# define GC_DEBUG -# endif -#endif - -#define GC_NEXT _PyGCHead_NEXT -#define GC_PREV _PyGCHead_PREV - -// update_refs() set this bit for all objects in current generation. -// subtract_refs() and move_unreachable() uses this to distinguish -// visited object is in GCing or not. -// -// move_unreachable() removes this flag from reachable objects. -// Only unreachable objects have this flag. -// -// No objects in interpreter have this flag after GC ends. -#define PREV_MASK_COLLECTING _PyGC_PREV_MASK_COLLECTING - -// Lowest bit of _gc_next is used for UNREACHABLE flag. -// -// This flag represents the object is in unreachable list in move_unreachable() -// -// Although this flag is used only in move_unreachable(), move_unreachable() -// doesn't clear this flag to skip unnecessary iteration. -// move_legacy_finalizers() removes this flag instead. -// Between them, unreachable list is not normal list and we can not use -// most gc_list_* functions for it. -#define NEXT_MASK_UNREACHABLE (1) - -/* Get an object's GC head */ -#define AS_GC(o) ((PyGC_Head *)(((char *)(o))-sizeof(PyGC_Head))) - -/* Get the object given the GC head */ -#define FROM_GC(g) ((PyObject *)(((char *)(g))+sizeof(PyGC_Head))) - -static inline int -gc_is_collecting(PyGC_Head *g) -{ - return (g->_gc_prev & PREV_MASK_COLLECTING) != 0; -} - -static inline void -gc_clear_collecting(PyGC_Head *g) -{ - g->_gc_prev &= ~PREV_MASK_COLLECTING; -} - -static inline Py_ssize_t -gc_get_refs(PyGC_Head *g) -{ - return (Py_ssize_t)(g->_gc_prev >> _PyGC_PREV_SHIFT); -} - -static inline void -gc_set_refs(PyGC_Head *g, Py_ssize_t refs) -{ - g->_gc_prev = (g->_gc_prev & ~_PyGC_PREV_MASK) - | ((uintptr_t)(refs) << _PyGC_PREV_SHIFT); -} - -static inline void -gc_reset_refs(PyGC_Head *g, Py_ssize_t refs) -{ - g->_gc_prev = (g->_gc_prev & _PyGC_PREV_MASK_FINALIZED) - | PREV_MASK_COLLECTING - | ((uintptr_t)(refs) << _PyGC_PREV_SHIFT); -} - -static inline void -gc_decref(PyGC_Head *g) -{ - _PyObject_ASSERT_WITH_MSG(FROM_GC(g), - gc_get_refs(g) > 0, - "refcount is too small"); - g->_gc_prev -= 1 << _PyGC_PREV_SHIFT; -} - -/* set for debugging information */ -#define DEBUG_STATS (1<<0) /* print collection statistics */ -#define DEBUG_COLLECTABLE (1<<1) /* print collectable objects */ -#define DEBUG_UNCOLLECTABLE (1<<2) /* print uncollectable objects */ -#define DEBUG_SAVEALL (1<<5) /* save all garbage in gc.garbage */ -#define DEBUG_LEAK DEBUG_COLLECTABLE | \ - DEBUG_UNCOLLECTABLE | \ - DEBUG_SAVEALL - -#define GEN_HEAD(gcstate, n) (&(gcstate)->generations[n].head) - - static GCState * get_gc_state(void) { @@ -137,1356 +18,10 @@ get_gc_state(void) return &interp->gc; } - -void -_PyGC_InitState(GCState *gcstate) -{ -#define INIT_HEAD(GEN) \ - do { \ - GEN.head._gc_next = (uintptr_t)&GEN.head; \ - GEN.head._gc_prev = (uintptr_t)&GEN.head; \ - } while (0) - - for (int i = 0; i < NUM_GENERATIONS; i++) { - assert(gcstate->generations[i].count == 0); - INIT_HEAD(gcstate->generations[i]); - }; - gcstate->generation0 = GEN_HEAD(gcstate, 0); - INIT_HEAD(gcstate->permanent_generation); - -#undef INIT_HEAD -} - - -PyStatus -_PyGC_Init(PyInterpreterState *interp) -{ - GCState *gcstate = &interp->gc; - - gcstate->garbage = PyList_New(0); - if (gcstate->garbage == NULL) { - return _PyStatus_NO_MEMORY(); - } - - gcstate->callbacks = PyList_New(0); - if (gcstate->callbacks == NULL) { - return _PyStatus_NO_MEMORY(); - } - - return _PyStatus_OK(); -} - - -/* -_gc_prev values ---------------- - -Between collections, _gc_prev is used for doubly linked list. - -Lowest two bits of _gc_prev are used for flags. -PREV_MASK_COLLECTING is used only while collecting and cleared before GC ends -or _PyObject_GC_UNTRACK() is called. - -During a collection, _gc_prev is temporary used for gc_refs, and the gc list -is singly linked until _gc_prev is restored. - -gc_refs - At the start of a collection, update_refs() copies the true refcount - to gc_refs, for each object in the generation being collected. - subtract_refs() then adjusts gc_refs so that it equals the number of - times an object is referenced directly from outside the generation - being collected. - -PREV_MASK_COLLECTING - Objects in generation being collected are marked PREV_MASK_COLLECTING in - update_refs(). - - -_gc_next values ---------------- - -_gc_next takes these values: - -0 - The object is not tracked - -!= 0 - Pointer to the next object in the GC list. - Additionally, lowest bit is used temporary for - NEXT_MASK_UNREACHABLE flag described below. - -NEXT_MASK_UNREACHABLE - move_unreachable() then moves objects not reachable (whether directly or - indirectly) from outside the generation into an "unreachable" set and - set this flag. - - Objects that are found to be reachable have gc_refs set to 1. - When this flag is set for the reachable object, the object must be in - "unreachable" set. - The flag is unset and the object is moved back to "reachable" set. - - move_legacy_finalizers() will remove this flag from "unreachable" set. -*/ - -/*** list functions ***/ - -static inline void -gc_list_init(PyGC_Head *list) -{ - // List header must not have flags. - // We can assign pointer by simple cast. - list->_gc_prev = (uintptr_t)list; - list->_gc_next = (uintptr_t)list; -} - -static inline int -gc_list_is_empty(PyGC_Head *list) -{ - return (list->_gc_next == (uintptr_t)list); -} - -/* Append `node` to `list`. */ -static inline void -gc_list_append(PyGC_Head *node, PyGC_Head *list) -{ - PyGC_Head *last = (PyGC_Head *)list->_gc_prev; - - // last <-> node - _PyGCHead_SET_PREV(node, last); - _PyGCHead_SET_NEXT(last, node); - - // node <-> list - _PyGCHead_SET_NEXT(node, list); - list->_gc_prev = (uintptr_t)node; -} - -/* Remove `node` from the gc list it's currently in. */ -static inline void -gc_list_remove(PyGC_Head *node) -{ - PyGC_Head *prev = GC_PREV(node); - PyGC_Head *next = GC_NEXT(node); - - _PyGCHead_SET_NEXT(prev, next); - _PyGCHead_SET_PREV(next, prev); - - node->_gc_next = 0; /* object is not currently tracked */ -} - -/* Move `node` from the gc list it's currently in (which is not explicitly - * named here) to the end of `list`. This is semantically the same as - * gc_list_remove(node) followed by gc_list_append(node, list). - */ -static void -gc_list_move(PyGC_Head *node, PyGC_Head *list) -{ - /* Unlink from current list. */ - PyGC_Head *from_prev = GC_PREV(node); - PyGC_Head *from_next = GC_NEXT(node); - _PyGCHead_SET_NEXT(from_prev, from_next); - _PyGCHead_SET_PREV(from_next, from_prev); - - /* Relink at end of new list. */ - // list must not have flags. So we can skip macros. - PyGC_Head *to_prev = (PyGC_Head*)list->_gc_prev; - _PyGCHead_SET_PREV(node, to_prev); - _PyGCHead_SET_NEXT(to_prev, node); - list->_gc_prev = (uintptr_t)node; - _PyGCHead_SET_NEXT(node, list); -} - -/* append list `from` onto list `to`; `from` becomes an empty list */ -static void -gc_list_merge(PyGC_Head *from, PyGC_Head *to) -{ - assert(from != to); - if (!gc_list_is_empty(from)) { - PyGC_Head *to_tail = GC_PREV(to); - PyGC_Head *from_head = GC_NEXT(from); - PyGC_Head *from_tail = GC_PREV(from); - assert(from_head != from); - assert(from_tail != from); - - _PyGCHead_SET_NEXT(to_tail, from_head); - _PyGCHead_SET_PREV(from_head, to_tail); - - _PyGCHead_SET_NEXT(from_tail, to); - _PyGCHead_SET_PREV(to, from_tail); - } - gc_list_init(from); -} - -static Py_ssize_t -gc_list_size(PyGC_Head *list) -{ - PyGC_Head *gc; - Py_ssize_t n = 0; - for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(gc)) { - n++; - } - return n; -} - -/* Walk the list and mark all objects as non-collecting */ -static inline void -gc_list_clear_collecting(PyGC_Head *collectable) -{ - PyGC_Head *gc; - for (gc = GC_NEXT(collectable); gc != collectable; gc = GC_NEXT(gc)) { - gc_clear_collecting(gc); - } -} - -/* Append objects in a GC list to a Python list. - * Return 0 if all OK, < 0 if error (out of memory for list) - */ -static int -append_objects(PyObject *py_list, PyGC_Head *gc_list) -{ - PyGC_Head *gc; - for (gc = GC_NEXT(gc_list); gc != gc_list; gc = GC_NEXT(gc)) { - PyObject *op = FROM_GC(gc); - if (op != py_list) { - if (PyList_Append(py_list, op)) { - return -1; /* exception */ - } - } - } - return 0; -} - -// Constants for validate_list's flags argument. -enum flagstates {collecting_clear_unreachable_clear, - collecting_clear_unreachable_set, - collecting_set_unreachable_clear, - collecting_set_unreachable_set}; - -#ifdef GC_DEBUG -// validate_list checks list consistency. And it works as document -// describing when flags are expected to be set / unset. -// `head` must be a doubly-linked gc list, although it's fine (expected!) if -// the prev and next pointers are "polluted" with flags. -// What's checked: -// - The `head` pointers are not polluted. -// - The objects' PREV_MASK_COLLECTING and NEXT_MASK_UNREACHABLE flags are all -// `set or clear, as specified by the 'flags' argument. -// - The prev and next pointers are mutually consistent. -static void -validate_list(PyGC_Head *head, enum flagstates flags) -{ - assert((head->_gc_prev & PREV_MASK_COLLECTING) == 0); - assert((head->_gc_next & NEXT_MASK_UNREACHABLE) == 0); - uintptr_t prev_value = 0, next_value = 0; - switch (flags) { - case collecting_clear_unreachable_clear: - break; - case collecting_set_unreachable_clear: - prev_value = PREV_MASK_COLLECTING; - break; - case collecting_clear_unreachable_set: - next_value = NEXT_MASK_UNREACHABLE; - break; - case collecting_set_unreachable_set: - prev_value = PREV_MASK_COLLECTING; - next_value = NEXT_MASK_UNREACHABLE; - break; - default: - assert(! "bad internal flags argument"); - } - PyGC_Head *prev = head; - PyGC_Head *gc = GC_NEXT(head); - while (gc != head) { - PyGC_Head *trueprev = GC_PREV(gc); - PyGC_Head *truenext = (PyGC_Head *)(gc->_gc_next & ~NEXT_MASK_UNREACHABLE); - assert(truenext != NULL); - assert(trueprev == prev); - assert((gc->_gc_prev & PREV_MASK_COLLECTING) == prev_value); - assert((gc->_gc_next & NEXT_MASK_UNREACHABLE) == next_value); - prev = gc; - gc = truenext; - } - assert(prev == GC_PREV(head)); -} -#else -#define validate_list(x, y) do{}while(0) -#endif - -/*** end of list stuff ***/ - - -/* Set all gc_refs = ob_refcnt. After this, gc_refs is > 0 and - * PREV_MASK_COLLECTING bit is set for all objects in containers. - */ -static void -update_refs(PyGC_Head *containers) -{ - PyGC_Head *next; - PyGC_Head *gc = GC_NEXT(containers); - - while (gc != containers) { - next = GC_NEXT(gc); - /* Move any object that might have become immortal to the - * permanent generation as the reference count is not accurately - * reflecting the actual number of live references to this object - */ - if (_Py_IsImmortal(FROM_GC(gc))) { - gc_list_move(gc, &get_gc_state()->permanent_generation.head); - gc = next; - continue; - } - gc_reset_refs(gc, Py_REFCNT(FROM_GC(gc))); - /* Python's cyclic gc should never see an incoming refcount - * of 0: if something decref'ed to 0, it should have been - * deallocated immediately at that time. - * Possible cause (if the assert triggers): a tp_dealloc - * routine left a gc-aware object tracked during its teardown - * phase, and did something-- or allowed something to happen -- - * that called back into Python. gc can trigger then, and may - * see the still-tracked dying object. Before this assert - * was added, such mistakes went on to allow gc to try to - * delete the object again. In a debug build, that caused - * a mysterious segfault, when _Py_ForgetReference tried - * to remove the object from the doubly-linked list of all - * objects a second time. In a release build, an actual - * double deallocation occurred, which leads to corruption - * of the allocator's internal bookkeeping pointers. That's - * so serious that maybe this should be a release-build - * check instead of an assert? - */ - _PyObject_ASSERT(FROM_GC(gc), gc_get_refs(gc) != 0); - gc = next; - } -} - -/* A traversal callback for subtract_refs. */ -static int -visit_decref(PyObject *op, void *parent) -{ - _PyObject_ASSERT(_PyObject_CAST(parent), !_PyObject_IsFreed(op)); - - if (_PyObject_IS_GC(op)) { - PyGC_Head *gc = AS_GC(op); - /* We're only interested in gc_refs for objects in the - * generation being collected, which can be recognized - * because only they have positive gc_refs. - */ - if (gc_is_collecting(gc)) { - gc_decref(gc); - } - } - return 0; -} - -/* Subtract internal references from gc_refs. After this, gc_refs is >= 0 - * for all objects in containers, and is GC_REACHABLE for all tracked gc - * objects not in containers. The ones with gc_refs > 0 are directly - * reachable from outside containers, and so can't be collected. - */ -static void -subtract_refs(PyGC_Head *containers) -{ - traverseproc traverse; - PyGC_Head *gc = GC_NEXT(containers); - for (; gc != containers; gc = GC_NEXT(gc)) { - PyObject *op = FROM_GC(gc); - traverse = Py_TYPE(op)->tp_traverse; - (void) traverse(op, - (visitproc)visit_decref, - op); - } -} - -/* A traversal callback for move_unreachable. */ -static int -visit_reachable(PyObject *op, PyGC_Head *reachable) -{ - if (!_PyObject_IS_GC(op)) { - return 0; - } - - PyGC_Head *gc = AS_GC(op); - const Py_ssize_t gc_refs = gc_get_refs(gc); - - // Ignore objects in other generation. - // This also skips objects "to the left" of the current position in - // move_unreachable's scan of the 'young' list - they've already been - // traversed, and no longer have the PREV_MASK_COLLECTING flag. - if (! gc_is_collecting(gc)) { - return 0; - } - // It would be a logic error elsewhere if the collecting flag were set on - // an untracked object. - assert(gc->_gc_next != 0); - - if (gc->_gc_next & NEXT_MASK_UNREACHABLE) { - /* This had gc_refs = 0 when move_unreachable got - * to it, but turns out it's reachable after all. - * Move it back to move_unreachable's 'young' list, - * and move_unreachable will eventually get to it - * again. - */ - // Manually unlink gc from unreachable list because the list functions - // don't work right in the presence of NEXT_MASK_UNREACHABLE flags. - PyGC_Head *prev = GC_PREV(gc); - PyGC_Head *next = (PyGC_Head*)(gc->_gc_next & ~NEXT_MASK_UNREACHABLE); - _PyObject_ASSERT(FROM_GC(prev), - prev->_gc_next & NEXT_MASK_UNREACHABLE); - _PyObject_ASSERT(FROM_GC(next), - next->_gc_next & NEXT_MASK_UNREACHABLE); - prev->_gc_next = gc->_gc_next; // copy NEXT_MASK_UNREACHABLE - _PyGCHead_SET_PREV(next, prev); - - gc_list_append(gc, reachable); - gc_set_refs(gc, 1); - } - else if (gc_refs == 0) { - /* This is in move_unreachable's 'young' list, but - * the traversal hasn't yet gotten to it. All - * we need to do is tell move_unreachable that it's - * reachable. - */ - gc_set_refs(gc, 1); - } - /* Else there's nothing to do. - * If gc_refs > 0, it must be in move_unreachable's 'young' - * list, and move_unreachable will eventually get to it. - */ - else { - _PyObject_ASSERT_WITH_MSG(op, gc_refs > 0, "refcount is too small"); - } - return 0; -} - -/* Move the unreachable objects from young to unreachable. After this, - * all objects in young don't have PREV_MASK_COLLECTING flag and - * unreachable have the flag. - * All objects in young after this are directly or indirectly reachable - * from outside the original young; and all objects in unreachable are - * not. - * - * This function restores _gc_prev pointer. young and unreachable are - * doubly linked list after this function. - * But _gc_next in unreachable list has NEXT_MASK_UNREACHABLE flag. - * So we can not gc_list_* functions for unreachable until we remove the flag. - */ -static void -move_unreachable(PyGC_Head *young, PyGC_Head *unreachable) -{ - // previous elem in the young list, used for restore gc_prev. - PyGC_Head *prev = young; - PyGC_Head *gc = GC_NEXT(young); - - /* Invariants: all objects "to the left" of us in young are reachable - * (directly or indirectly) from outside the young list as it was at entry. - * - * All other objects from the original young "to the left" of us are in - * unreachable now, and have NEXT_MASK_UNREACHABLE. All objects to the - * left of us in 'young' now have been scanned, and no objects here - * or to the right have been scanned yet. - */ - - while (gc != young) { - if (gc_get_refs(gc)) { - /* gc is definitely reachable from outside the - * original 'young'. Mark it as such, and traverse - * its pointers to find any other objects that may - * be directly reachable from it. Note that the - * call to tp_traverse may append objects to young, - * so we have to wait until it returns to determine - * the next object to visit. - */ - PyObject *op = FROM_GC(gc); - traverseproc traverse = Py_TYPE(op)->tp_traverse; - _PyObject_ASSERT_WITH_MSG(op, gc_get_refs(gc) > 0, - "refcount is too small"); - // NOTE: visit_reachable may change gc->_gc_next when - // young->_gc_prev == gc. Don't do gc = GC_NEXT(gc) before! - (void) traverse(op, - (visitproc)visit_reachable, - (void *)young); - // relink gc_prev to prev element. - _PyGCHead_SET_PREV(gc, prev); - // gc is not COLLECTING state after here. - gc_clear_collecting(gc); - prev = gc; - } - else { - /* This *may* be unreachable. To make progress, - * assume it is. gc isn't directly reachable from - * any object we've already traversed, but may be - * reachable from an object we haven't gotten to yet. - * visit_reachable will eventually move gc back into - * young if that's so, and we'll see it again. - */ - // Move gc to unreachable. - // No need to gc->next->prev = prev because it is single linked. - prev->_gc_next = gc->_gc_next; - - // We can't use gc_list_append() here because we use - // NEXT_MASK_UNREACHABLE here. - PyGC_Head *last = GC_PREV(unreachable); - // NOTE: Since all objects in unreachable set has - // NEXT_MASK_UNREACHABLE flag, we set it unconditionally. - // But this may pollute the unreachable list head's 'next' pointer - // too. That's semantically senseless but expedient here - the - // damage is repaired when this function ends. - last->_gc_next = (NEXT_MASK_UNREACHABLE | (uintptr_t)gc); - _PyGCHead_SET_PREV(gc, last); - gc->_gc_next = (NEXT_MASK_UNREACHABLE | (uintptr_t)unreachable); - unreachable->_gc_prev = (uintptr_t)gc; - } - gc = (PyGC_Head*)prev->_gc_next; - } - // young->_gc_prev must be last element remained in the list. - young->_gc_prev = (uintptr_t)prev; - // don't let the pollution of the list head's next pointer leak - unreachable->_gc_next &= ~NEXT_MASK_UNREACHABLE; -} - -static void -untrack_tuples(PyGC_Head *head) -{ - PyGC_Head *next, *gc = GC_NEXT(head); - while (gc != head) { - PyObject *op = FROM_GC(gc); - next = GC_NEXT(gc); - if (PyTuple_CheckExact(op)) { - _PyTuple_MaybeUntrack(op); - } - gc = next; - } -} - -/* Try to untrack all currently tracked dictionaries */ -static void -untrack_dicts(PyGC_Head *head) -{ - PyGC_Head *next, *gc = GC_NEXT(head); - while (gc != head) { - PyObject *op = FROM_GC(gc); - next = GC_NEXT(gc); - if (PyDict_CheckExact(op)) { - _PyDict_MaybeUntrack(op); - } - gc = next; - } -} - -/* Return true if object has a pre-PEP 442 finalization method. */ -static int -has_legacy_finalizer(PyObject *op) -{ - return Py_TYPE(op)->tp_del != NULL; -} - -/* Move the objects in unreachable with tp_del slots into `finalizers`. - * - * This function also removes NEXT_MASK_UNREACHABLE flag - * from _gc_next in unreachable. - */ -static void -move_legacy_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers) -{ - PyGC_Head *gc, *next; - assert((unreachable->_gc_next & NEXT_MASK_UNREACHABLE) == 0); - - /* March over unreachable. Move objects with finalizers into - * `finalizers`. - */ - for (gc = GC_NEXT(unreachable); gc != unreachable; gc = next) { - PyObject *op = FROM_GC(gc); - - _PyObject_ASSERT(op, gc->_gc_next & NEXT_MASK_UNREACHABLE); - gc->_gc_next &= ~NEXT_MASK_UNREACHABLE; - next = (PyGC_Head*)gc->_gc_next; - - if (has_legacy_finalizer(op)) { - gc_clear_collecting(gc); - gc_list_move(gc, finalizers); - } - } -} - -static inline void -clear_unreachable_mask(PyGC_Head *unreachable) -{ - /* Check that the list head does not have the unreachable bit set */ - assert(((uintptr_t)unreachable & NEXT_MASK_UNREACHABLE) == 0); - - PyGC_Head *gc, *next; - assert((unreachable->_gc_next & NEXT_MASK_UNREACHABLE) == 0); - for (gc = GC_NEXT(unreachable); gc != unreachable; gc = next) { - _PyObject_ASSERT((PyObject*)FROM_GC(gc), gc->_gc_next & NEXT_MASK_UNREACHABLE); - gc->_gc_next &= ~NEXT_MASK_UNREACHABLE; - next = (PyGC_Head*)gc->_gc_next; - } - validate_list(unreachable, collecting_set_unreachable_clear); -} - -/* A traversal callback for move_legacy_finalizer_reachable. */ -static int -visit_move(PyObject *op, PyGC_Head *tolist) -{ - if (_PyObject_IS_GC(op)) { - PyGC_Head *gc = AS_GC(op); - if (gc_is_collecting(gc)) { - gc_list_move(gc, tolist); - gc_clear_collecting(gc); - } - } - return 0; -} - -/* Move objects that are reachable from finalizers, from the unreachable set - * into finalizers set. - */ -static void -move_legacy_finalizer_reachable(PyGC_Head *finalizers) -{ - traverseproc traverse; - PyGC_Head *gc = GC_NEXT(finalizers); - for (; gc != finalizers; gc = GC_NEXT(gc)) { - /* Note that the finalizers list may grow during this. */ - traverse = Py_TYPE(FROM_GC(gc))->tp_traverse; - (void) traverse(FROM_GC(gc), - (visitproc)visit_move, - (void *)finalizers); - } -} - -/* Clear all weakrefs to unreachable objects, and if such a weakref has a - * callback, invoke it if necessary. Note that it's possible for such - * weakrefs to be outside the unreachable set -- indeed, those are precisely - * the weakrefs whose callbacks must be invoked. See gc_weakref.txt for - * overview & some details. Some weakrefs with callbacks may be reclaimed - * directly by this routine; the number reclaimed is the return value. Other - * weakrefs with callbacks may be moved into the `old` generation. Objects - * moved into `old` have gc_refs set to GC_REACHABLE; the objects remaining in - * unreachable are left at GC_TENTATIVELY_UNREACHABLE. When this returns, - * no object in `unreachable` is weakly referenced anymore. - */ -static int -handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old) -{ - PyGC_Head *gc; - PyObject *op; /* generally FROM_GC(gc) */ - PyWeakReference *wr; /* generally a cast of op */ - PyGC_Head wrcb_to_call; /* weakrefs with callbacks to call */ - PyGC_Head *next; - int num_freed = 0; - - gc_list_init(&wrcb_to_call); - - /* Clear all weakrefs to the objects in unreachable. If such a weakref - * also has a callback, move it into `wrcb_to_call` if the callback - * needs to be invoked. Note that we cannot invoke any callbacks until - * all weakrefs to unreachable objects are cleared, lest the callback - * resurrect an unreachable object via a still-active weakref. We - * make another pass over wrcb_to_call, invoking callbacks, after this - * pass completes. - */ - for (gc = GC_NEXT(unreachable); gc != unreachable; gc = next) { - PyWeakReference **wrlist; - - op = FROM_GC(gc); - next = GC_NEXT(gc); - - if (PyWeakref_Check(op)) { - /* A weakref inside the unreachable set must be cleared. If we - * allow its callback to execute inside delete_garbage(), it - * could expose objects that have tp_clear already called on - * them. Or, it could resurrect unreachable objects. One way - * this can happen is if some container objects do not implement - * tp_traverse. Then, wr_object can be outside the unreachable - * set but can be deallocated as a result of breaking the - * reference cycle. If we don't clear the weakref, the callback - * will run and potentially cause a crash. See bpo-38006 for - * one example. - */ - _PyWeakref_ClearRef((PyWeakReference *)op); - } - - if (! _PyType_SUPPORTS_WEAKREFS(Py_TYPE(op))) - continue; - - /* It supports weakrefs. Does it have any? - * - * This is never triggered for static types so we can avoid the - * (slightly) more costly _PyObject_GET_WEAKREFS_LISTPTR(). - */ - wrlist = _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(op); - - /* `op` may have some weakrefs. March over the list, clear - * all the weakrefs, and move the weakrefs with callbacks - * that must be called into wrcb_to_call. - */ - for (wr = *wrlist; wr != NULL; wr = *wrlist) { - PyGC_Head *wrasgc; /* AS_GC(wr) */ - - /* _PyWeakref_ClearRef clears the weakref but leaves - * the callback pointer intact. Obscure: it also - * changes *wrlist. - */ - _PyObject_ASSERT((PyObject *)wr, wr->wr_object == op); - _PyWeakref_ClearRef(wr); - _PyObject_ASSERT((PyObject *)wr, wr->wr_object == Py_None); - if (wr->wr_callback == NULL) { - /* no callback */ - continue; - } - - /* Headache time. `op` is going away, and is weakly referenced by - * `wr`, which has a callback. Should the callback be invoked? If wr - * is also trash, no: - * - * 1. There's no need to call it. The object and the weakref are - * both going away, so it's legitimate to pretend the weakref is - * going away first. The user has to ensure a weakref outlives its - * referent if they want a guarantee that the wr callback will get - * invoked. - * - * 2. It may be catastrophic to call it. If the callback is also in - * cyclic trash (CT), then although the CT is unreachable from - * outside the current generation, CT may be reachable from the - * callback. Then the callback could resurrect insane objects. - * - * Since the callback is never needed and may be unsafe in this case, - * wr is simply left in the unreachable set. Note that because we - * already called _PyWeakref_ClearRef(wr), its callback will never - * trigger. - * - * OTOH, if wr isn't part of CT, we should invoke the callback: the - * weakref outlived the trash. Note that since wr isn't CT in this - * case, its callback can't be CT either -- wr acted as an external - * root to this generation, and therefore its callback did too. So - * nothing in CT is reachable from the callback either, so it's hard - * to imagine how calling it later could create a problem for us. wr - * is moved to wrcb_to_call in this case. - */ - if (gc_is_collecting(AS_GC(wr))) { - /* it should already have been cleared above */ - assert(wr->wr_object == Py_None); - continue; - } - - /* Create a new reference so that wr can't go away - * before we can process it again. - */ - Py_INCREF(wr); - - /* Move wr to wrcb_to_call, for the next pass. */ - wrasgc = AS_GC(wr); - assert(wrasgc != next); /* wrasgc is reachable, but - next isn't, so they can't - be the same */ - gc_list_move(wrasgc, &wrcb_to_call); - } - } - - /* Invoke the callbacks we decided to honor. It's safe to invoke them - * because they can't reference unreachable objects. - */ - while (! gc_list_is_empty(&wrcb_to_call)) { - PyObject *temp; - PyObject *callback; - - gc = (PyGC_Head*)wrcb_to_call._gc_next; - op = FROM_GC(gc); - _PyObject_ASSERT(op, PyWeakref_Check(op)); - wr = (PyWeakReference *)op; - callback = wr->wr_callback; - _PyObject_ASSERT(op, callback != NULL); - - /* copy-paste of weakrefobject.c's handle_callback() */ - temp = PyObject_CallOneArg(callback, (PyObject *)wr); - if (temp == NULL) - PyErr_WriteUnraisable(callback); - else - Py_DECREF(temp); - - /* Give up the reference we created in the first pass. When - * op's refcount hits 0 (which it may or may not do right now), - * op's tp_dealloc will decref op->wr_callback too. Note - * that the refcount probably will hit 0 now, and because this - * weakref was reachable to begin with, gc didn't already - * add it to its count of freed objects. Example: a reachable - * weak value dict maps some key to this reachable weakref. - * The callback removes this key->weakref mapping from the - * dict, leaving no other references to the weakref (excepting - * ours). - */ - Py_DECREF(op); - if (wrcb_to_call._gc_next == (uintptr_t)gc) { - /* object is still alive -- move it */ - gc_list_move(gc, old); - } - else { - ++num_freed; - } - } - - return num_freed; -} - -static void -debug_cycle(const char *msg, PyObject *op) -{ - PySys_FormatStderr("gc: %s <%s %p>\n", - msg, Py_TYPE(op)->tp_name, op); -} - -/* Handle uncollectable garbage (cycles with tp_del slots, and stuff reachable - * only from such cycles). - * If DEBUG_SAVEALL, all objects in finalizers are appended to the module - * garbage list (a Python list), else only the objects in finalizers with - * __del__ methods are appended to garbage. All objects in finalizers are - * merged into the old list regardless. - */ -static void -handle_legacy_finalizers(PyThreadState *tstate, - GCState *gcstate, - PyGC_Head *finalizers, PyGC_Head *old) -{ - assert(!_PyErr_Occurred(tstate)); - assert(gcstate->garbage != NULL); - - PyGC_Head *gc = GC_NEXT(finalizers); - for (; gc != finalizers; gc = GC_NEXT(gc)) { - PyObject *op = FROM_GC(gc); - - if ((gcstate->debug & DEBUG_SAVEALL) || has_legacy_finalizer(op)) { - if (PyList_Append(gcstate->garbage, op) < 0) { - _PyErr_Clear(tstate); - break; - } - } - } - - gc_list_merge(finalizers, old); -} - -/* Run first-time finalizers (if any) on all the objects in collectable. - * Note that this may remove some (or even all) of the objects from the - * list, due to refcounts falling to 0. - */ -static void -finalize_garbage(PyThreadState *tstate, PyGC_Head *collectable) -{ - destructor finalize; - PyGC_Head seen; - - /* While we're going through the loop, `finalize(op)` may cause op, or - * other objects, to be reclaimed via refcounts falling to zero. So - * there's little we can rely on about the structure of the input - * `collectable` list across iterations. For safety, we always take the - * first object in that list and move it to a temporary `seen` list. - * If objects vanish from the `collectable` and `seen` lists we don't - * care. - */ - gc_list_init(&seen); - - while (!gc_list_is_empty(collectable)) { - PyGC_Head *gc = GC_NEXT(collectable); - PyObject *op = FROM_GC(gc); - gc_list_move(gc, &seen); - if (!_PyGCHead_FINALIZED(gc) && - (finalize = Py_TYPE(op)->tp_finalize) != NULL) { - _PyGCHead_SET_FINALIZED(gc); - Py_INCREF(op); - finalize(op); - assert(!_PyErr_Occurred(tstate)); - Py_DECREF(op); - } - } - gc_list_merge(&seen, collectable); -} - -/* Break reference cycles by clearing the containers involved. This is - * tricky business as the lists can be changing and we don't know which - * objects may be freed. It is possible I screwed something up here. - */ -static void -delete_garbage(PyThreadState *tstate, GCState *gcstate, - PyGC_Head *collectable, PyGC_Head *old) -{ - assert(!_PyErr_Occurred(tstate)); - - while (!gc_list_is_empty(collectable)) { - PyGC_Head *gc = GC_NEXT(collectable); - PyObject *op = FROM_GC(gc); - - _PyObject_ASSERT_WITH_MSG(op, Py_REFCNT(op) > 0, - "refcount is too small"); - - if (gcstate->debug & DEBUG_SAVEALL) { - assert(gcstate->garbage != NULL); - if (PyList_Append(gcstate->garbage, op) < 0) { - _PyErr_Clear(tstate); - } - } - else { - inquiry clear; - if ((clear = Py_TYPE(op)->tp_clear) != NULL) { - Py_INCREF(op); - (void) clear(op); - if (_PyErr_Occurred(tstate)) { - _PyErr_WriteUnraisableMsg("in tp_clear of", - (PyObject*)Py_TYPE(op)); - } - Py_DECREF(op); - } - } - if (GC_NEXT(collectable) == gc) { - /* object is still alive, move it, it may die later */ - gc_clear_collecting(gc); - gc_list_move(gc, old); - } - } -} - -/* Clear all free lists - * All free lists are cleared during the collection of the highest generation. - * Allocated items in the free list may keep a pymalloc arena occupied. - * Clearing the free lists may give back memory to the OS earlier. - */ -static void -clear_freelists(PyInterpreterState *interp) -{ - _PyTuple_ClearFreeList(interp); - _PyFloat_ClearFreeList(interp); - _PyList_ClearFreeList(interp); - _PyDict_ClearFreeList(interp); - _PyAsyncGen_ClearFreeLists(interp); - _PyContext_ClearFreeList(interp); -} - -// Show stats for objects in each generations -static void -show_stats_each_generations(GCState *gcstate) -{ - char buf[100]; - size_t pos = 0; - - for (int i = 0; i < NUM_GENERATIONS && pos < sizeof(buf); i++) { - pos += PyOS_snprintf(buf+pos, sizeof(buf)-pos, - " %zd", - gc_list_size(GEN_HEAD(gcstate, i))); - } - - PySys_FormatStderr( - "gc: objects in each generation:%s\n" - "gc: objects in permanent generation: %zd\n", - buf, gc_list_size(&gcstate->permanent_generation.head)); -} - -/* Deduce which objects among "base" are unreachable from outside the list - and move them to 'unreachable'. The process consist in the following steps: - -1. Copy all reference counts to a different field (gc_prev is used to hold - this copy to save memory). -2. Traverse all objects in "base" and visit all referred objects using - "tp_traverse" and for every visited object, subtract 1 to the reference - count (the one that we copied in the previous step). After this step, all - objects that can be reached directly from outside must have strictly positive - reference count, while all unreachable objects must have a count of exactly 0. -3. Identify all unreachable objects (the ones with 0 reference count) and move - them to the "unreachable" list. This step also needs to move back to "base" all - objects that were initially marked as unreachable but are referred transitively - by the reachable objects (the ones with strictly positive reference count). - -Contracts: - - * The "base" has to be a valid list with no mask set. - - * The "unreachable" list must be uninitialized (this function calls - gc_list_init over 'unreachable'). - -IMPORTANT: This function leaves 'unreachable' with the NEXT_MASK_UNREACHABLE -flag set but it does not clear it to skip unnecessary iteration. Before the -flag is cleared (for example, by using 'clear_unreachable_mask' function or -by a call to 'move_legacy_finalizers'), the 'unreachable' list is not a normal -list and we can not use most gc_list_* functions for it. */ -static inline void -deduce_unreachable(PyGC_Head *base, PyGC_Head *unreachable) { - validate_list(base, collecting_clear_unreachable_clear); - /* Using ob_refcnt and gc_refs, calculate which objects in the - * container set are reachable from outside the set (i.e., have a - * refcount greater than 0 when all the references within the - * set are taken into account). - */ - update_refs(base); // gc_prev is used for gc_refs - subtract_refs(base); - - /* Leave everything reachable from outside base in base, and move - * everything else (in base) to unreachable. - * - * NOTE: This used to move the reachable objects into a reachable - * set instead. But most things usually turn out to be reachable, - * so it's more efficient to move the unreachable things. It "sounds slick" - * to move the unreachable objects, until you think about it - the reason it - * pays isn't actually obvious. - * - * Suppose we create objects A, B, C in that order. They appear in the young - * generation in the same order. If B points to A, and C to B, and C is - * reachable from outside, then the adjusted refcounts will be 0, 0, and 1 - * respectively. - * - * When move_unreachable finds A, A is moved to the unreachable list. The - * same for B when it's first encountered. Then C is traversed, B is moved - * _back_ to the reachable list. B is eventually traversed, and then A is - * moved back to the reachable list. - * - * So instead of not moving at all, the reachable objects B and A are moved - * twice each. Why is this a win? A straightforward algorithm to move the - * reachable objects instead would move A, B, and C once each. - * - * The key is that this dance leaves the objects in order C, B, A - it's - * reversed from the original order. On all _subsequent_ scans, none of - * them will move. Since most objects aren't in cycles, this can save an - * unbounded number of moves across an unbounded number of later collections. - * It can cost more only the first time the chain is scanned. - * - * Drawback: move_unreachable is also used to find out what's still trash - * after finalizers may resurrect objects. In _that_ case most unreachable - * objects will remain unreachable, so it would be more efficient to move - * the reachable objects instead. But this is a one-time cost, probably not - * worth complicating the code to speed just a little. - */ - gc_list_init(unreachable); - move_unreachable(base, unreachable); // gc_prev is pointer again - validate_list(base, collecting_clear_unreachable_clear); - validate_list(unreachable, collecting_set_unreachable_set); -} - -/* Handle objects that may have resurrected after a call to 'finalize_garbage', moving - them to 'old_generation' and placing the rest on 'still_unreachable'. - - Contracts: - * After this function 'unreachable' must not be used anymore and 'still_unreachable' - will contain the objects that did not resurrect. - - * The "still_unreachable" list must be uninitialized (this function calls - gc_list_init over 'still_unreachable'). - -IMPORTANT: After a call to this function, the 'still_unreachable' set will have the -PREV_MARK_COLLECTING set, but the objects in this set are going to be removed so -we can skip the expense of clearing the flag to avoid extra iteration. */ -static inline void -handle_resurrected_objects(PyGC_Head *unreachable, PyGC_Head* still_unreachable, - PyGC_Head *old_generation) -{ - // Remove the PREV_MASK_COLLECTING from unreachable - // to prepare it for a new call to 'deduce_unreachable' - gc_list_clear_collecting(unreachable); - - // After the call to deduce_unreachable, the 'still_unreachable' set will - // have the PREV_MARK_COLLECTING set, but the objects are going to be - // removed so we can skip the expense of clearing the flag. - PyGC_Head* resurrected = unreachable; - deduce_unreachable(resurrected, still_unreachable); - clear_unreachable_mask(still_unreachable); - - // Move the resurrected objects to the old generation for future collection. - gc_list_merge(resurrected, old_generation); -} - -/* This is the main function. Read this to understand how the - * collection process works. */ -static Py_ssize_t -gc_collect_main(PyThreadState *tstate, int generation, - Py_ssize_t *n_collected, Py_ssize_t *n_uncollectable, - int nofail) -{ - int i; - Py_ssize_t m = 0; /* # objects collected */ - Py_ssize_t n = 0; /* # unreachable objects that couldn't be collected */ - PyGC_Head *young; /* the generation we are examining */ - PyGC_Head *old; /* next older generation */ - PyGC_Head unreachable; /* non-problematic unreachable trash */ - PyGC_Head finalizers; /* objects with, & reachable from, __del__ */ - PyGC_Head *gc; - _PyTime_t t1 = 0; /* initialize to prevent a compiler warning */ - GCState *gcstate = &tstate->interp->gc; - - // gc_collect_main() must not be called before _PyGC_Init - // or after _PyGC_Fini() - assert(gcstate->garbage != NULL); - assert(!_PyErr_Occurred(tstate)); - - if (gcstate->debug & DEBUG_STATS) { - PySys_WriteStderr("gc: collecting generation %d...\n", generation); - show_stats_each_generations(gcstate); - t1 = _PyTime_GetPerfCounter(); - } - - if (PyDTrace_GC_START_ENABLED()) - PyDTrace_GC_START(generation); - - /* update collection and allocation counters */ - if (generation+1 < NUM_GENERATIONS) - gcstate->generations[generation+1].count += 1; - for (i = 0; i <= generation; i++) - gcstate->generations[i].count = 0; - - /* merge younger generations with one we are currently collecting */ - for (i = 0; i < generation; i++) { - gc_list_merge(GEN_HEAD(gcstate, i), GEN_HEAD(gcstate, generation)); - } - - /* handy references */ - young = GEN_HEAD(gcstate, generation); - if (generation < NUM_GENERATIONS-1) - old = GEN_HEAD(gcstate, generation+1); - else - old = young; - validate_list(old, collecting_clear_unreachable_clear); - - deduce_unreachable(young, &unreachable); - - untrack_tuples(young); - /* Move reachable objects to next generation. */ - if (young != old) { - if (generation == NUM_GENERATIONS - 2) { - gcstate->long_lived_pending += gc_list_size(young); - } - gc_list_merge(young, old); - } - else { - /* We only un-track dicts in full collections, to avoid quadratic - dict build-up. See issue #14775. */ - untrack_dicts(young); - gcstate->long_lived_pending = 0; - gcstate->long_lived_total = gc_list_size(young); - } - - /* All objects in unreachable are trash, but objects reachable from - * legacy finalizers (e.g. tp_del) can't safely be deleted. - */ - gc_list_init(&finalizers); - // NEXT_MASK_UNREACHABLE is cleared here. - // After move_legacy_finalizers(), unreachable is normal list. - move_legacy_finalizers(&unreachable, &finalizers); - /* finalizers contains the unreachable objects with a legacy finalizer; - * unreachable objects reachable *from* those are also uncollectable, - * and we move those into the finalizers list too. - */ - move_legacy_finalizer_reachable(&finalizers); - - validate_list(&finalizers, collecting_clear_unreachable_clear); - validate_list(&unreachable, collecting_set_unreachable_clear); - - /* Print debugging information. */ - if (gcstate->debug & DEBUG_COLLECTABLE) { - for (gc = GC_NEXT(&unreachable); gc != &unreachable; gc = GC_NEXT(gc)) { - debug_cycle("collectable", FROM_GC(gc)); - } - } - - /* Clear weakrefs and invoke callbacks as necessary. */ - m += handle_weakrefs(&unreachable, old); - - validate_list(old, collecting_clear_unreachable_clear); - validate_list(&unreachable, collecting_set_unreachable_clear); - - /* Call tp_finalize on objects which have one. */ - finalize_garbage(tstate, &unreachable); - - /* Handle any objects that may have resurrected after the call - * to 'finalize_garbage' and continue the collection with the - * objects that are still unreachable */ - PyGC_Head final_unreachable; - handle_resurrected_objects(&unreachable, &final_unreachable, old); - - /* Call tp_clear on objects in the final_unreachable set. This will cause - * the reference cycles to be broken. It may also cause some objects - * in finalizers to be freed. - */ - m += gc_list_size(&final_unreachable); - delete_garbage(tstate, gcstate, &final_unreachable, old); - - /* Collect statistics on uncollectable objects found and print - * debugging information. */ - for (gc = GC_NEXT(&finalizers); gc != &finalizers; gc = GC_NEXT(gc)) { - n++; - if (gcstate->debug & DEBUG_UNCOLLECTABLE) - debug_cycle("uncollectable", FROM_GC(gc)); - } - if (gcstate->debug & DEBUG_STATS) { - double d = _PyTime_AsSecondsDouble(_PyTime_GetPerfCounter() - t1); - PySys_WriteStderr( - "gc: done, %zd unreachable, %zd uncollectable, %.4fs elapsed\n", - n+m, n, d); - } - - /* Append instances in the uncollectable set to a Python - * reachable list of garbage. The programmer has to deal with - * this if they insist on creating this type of structure. - */ - handle_legacy_finalizers(tstate, gcstate, &finalizers, old); - validate_list(old, collecting_clear_unreachable_clear); - - /* Clear free list only during the collection of the highest - * generation */ - if (generation == NUM_GENERATIONS-1) { - clear_freelists(tstate->interp); - } - - if (_PyErr_Occurred(tstate)) { - if (nofail) { - _PyErr_Clear(tstate); - } - else { - _PyErr_WriteUnraisableMsg("in garbage collection", NULL); - } - } - - /* Update stats */ - if (n_collected) { - *n_collected = m; - } - if (n_uncollectable) { - *n_uncollectable = n; - } - - struct gc_generation_stats *stats = &gcstate->generation_stats[generation]; - stats->collections++; - stats->collected += m; - stats->uncollectable += n; - - if (PyDTrace_GC_DONE_ENABLED()) { - PyDTrace_GC_DONE(n + m); - } - - assert(!_PyErr_Occurred(tstate)); - return n + m; -} - -/* Invoke progress callbacks to notify clients that garbage collection - * is starting or stopping - */ -static void -invoke_gc_callback(PyThreadState *tstate, const char *phase, - int generation, Py_ssize_t collected, - Py_ssize_t uncollectable) -{ - assert(!_PyErr_Occurred(tstate)); - - /* we may get called very early */ - GCState *gcstate = &tstate->interp->gc; - if (gcstate->callbacks == NULL) { - return; - } - - /* The local variable cannot be rebound, check it for sanity */ - assert(PyList_CheckExact(gcstate->callbacks)); - PyObject *info = NULL; - if (PyList_GET_SIZE(gcstate->callbacks) != 0) { - info = Py_BuildValue("{sisnsn}", - "generation", generation, - "collected", collected, - "uncollectable", uncollectable); - if (info == NULL) { - PyErr_WriteUnraisable(NULL); - return; - } - } - - PyObject *phase_obj = PyUnicode_FromString(phase); - if (phase_obj == NULL) { - Py_XDECREF(info); - PyErr_WriteUnraisable(NULL); - return; - } - - PyObject *stack[] = {phase_obj, info}; - for (Py_ssize_t i=0; i<PyList_GET_SIZE(gcstate->callbacks); i++) { - PyObject *r, *cb = PyList_GET_ITEM(gcstate->callbacks, i); - Py_INCREF(cb); /* make sure cb doesn't go away */ - r = PyObject_Vectorcall(cb, stack, 2, NULL); - if (r == NULL) { - PyErr_WriteUnraisable(cb); - } - else { - Py_DECREF(r); - } - Py_DECREF(cb); - } - Py_DECREF(phase_obj); - Py_XDECREF(info); - assert(!_PyErr_Occurred(tstate)); -} - -/* Perform garbage collection of a generation and invoke - * progress callbacks. - */ -static Py_ssize_t -gc_collect_with_callback(PyThreadState *tstate, int generation) -{ - assert(!_PyErr_Occurred(tstate)); - Py_ssize_t result, collected, uncollectable; - invoke_gc_callback(tstate, "start", generation, 0, 0); - result = gc_collect_main(tstate, generation, &collected, &uncollectable, 0); - invoke_gc_callback(tstate, "stop", generation, collected, uncollectable); - assert(!_PyErr_Occurred(tstate)); - return result; -} - -static Py_ssize_t -gc_collect_generations(PyThreadState *tstate) -{ - GCState *gcstate = &tstate->interp->gc; - /* Find the oldest generation (highest numbered) where the count - * exceeds the threshold. Objects in the that generation and - * generations younger than it will be collected. */ - Py_ssize_t n = 0; - for (int i = NUM_GENERATIONS-1; i >= 0; i--) { - if (gcstate->generations[i].count > gcstate->generations[i].threshold) { - /* Avoid quadratic performance degradation in number - of tracked objects (see also issue #4074): - - To limit the cost of garbage collection, there are two strategies; - - make each collection faster, e.g. by scanning fewer objects - - do less collections - This heuristic is about the latter strategy. - - In addition to the various configurable thresholds, we only trigger a - full collection if the ratio - - long_lived_pending / long_lived_total - - is above a given value (hardwired to 25%). - - The reason is that, while "non-full" collections (i.e., collections of - the young and middle generations) will always examine roughly the same - number of objects -- determined by the aforementioned thresholds --, - the cost of a full collection is proportional to the total number of - long-lived objects, which is virtually unbounded. - - Indeed, it has been remarked that doing a full collection every - <constant number> of object creations entails a dramatic performance - degradation in workloads which consist in creating and storing lots of - long-lived objects (e.g. building a large list of GC-tracked objects would - show quadratic performance, instead of linear as expected: see issue #4074). - - Using the above ratio, instead, yields amortized linear performance in - the total number of objects (the effect of which can be summarized - thusly: "each full garbage collection is more and more costly as the - number of objects grows, but we do fewer and fewer of them"). - - This heuristic was suggested by Martin von Löwis on python-dev in - June 2008. His original analysis and proposal can be found at: - http://mail.python.org/pipermail/python-dev/2008-June/080579.html - */ - if (i == NUM_GENERATIONS - 1 - && gcstate->long_lived_pending < gcstate->long_lived_total / 4) - continue; - n = gc_collect_with_callback(tstate, i); - break; - } - } - return n; -} - +/*[clinic input] +module gc +[clinic start generated code]*/ +/*[clinic end generated code: output=da39a3ee5e6b4b0d input=b5c9690ecc842d79]*/ #include "clinic/gcmodule.c.h" /*[clinic input] @@ -1555,18 +90,7 @@ gc_collect_impl(PyObject *module, int generation) return -1; } - GCState *gcstate = &tstate->interp->gc; - Py_ssize_t n; - if (gcstate->collecting) { - /* already collecting, don't do anything */ - n = 0; - } - else { - gcstate->collecting = 1; - n = gc_collect_with_callback(tstate, generation); - gcstate->collecting = 0; - } - return n; + return _PyGC_Collect(tstate, generation, _Py_GC_REASON_MANUAL); } /*[clinic input] @@ -1610,24 +134,41 @@ gc_get_debug_impl(PyObject *module) return gcstate->debug; } -PyDoc_STRVAR(gc_set_thresh__doc__, -"set_threshold(threshold0, [threshold1, threshold2]) -> None\n" -"\n" -"Sets the collection thresholds. Setting threshold0 to zero disables\n" -"collection.\n"); +/*[clinic input] +gc.set_threshold + + threshold0: int + [ + threshold1: int + [ + threshold2: int + ] + ] + / + +Set the collection thresholds (the collection frequency). + +Setting 'threshold0' to zero disables collection. +[clinic start generated code]*/ static PyObject * -gc_set_threshold(PyObject *self, PyObject *args) +gc_set_threshold_impl(PyObject *module, int threshold0, int group_right_1, + int threshold1, int group_right_2, int threshold2) +/*[clinic end generated code: output=2e3c7c7dd59060f3 input=0d9612db50984eec]*/ { GCState *gcstate = get_gc_state(); - if (!PyArg_ParseTuple(args, "i|ii:set_threshold", - &gcstate->generations[0].threshold, - &gcstate->generations[1].threshold, - &gcstate->generations[2].threshold)) - return NULL; - for (int i = 3; i < NUM_GENERATIONS; i++) { + + gcstate->generations[0].threshold = threshold0; + if (group_right_1) { + gcstate->generations[1].threshold = threshold1; + } + if (group_right_2) { + gcstate->generations[2].threshold = threshold2; + /* generations higher than 2 get the same threshold */ - gcstate->generations[i].threshold = gcstate->generations[2].threshold; + for (int i = 3; i < NUM_GENERATIONS; i++) { + gcstate->generations[i].threshold = gcstate->generations[2].threshold; + } } Py_RETURN_NONE; } @@ -1660,104 +201,100 @@ gc_get_count_impl(PyObject *module) /*[clinic end generated code: output=354012e67b16398f input=a392794a08251751]*/ { GCState *gcstate = get_gc_state(); + +#ifdef Py_GIL_DISABLED + _PyThreadStateImpl *tstate = (_PyThreadStateImpl *)_PyThreadState_GET(); + struct _gc_thread_state *gc = &tstate->gc; + + // Flush the local allocation count to the global count + _Py_atomic_add_int(&gcstate->generations[0].count, (int)gc->alloc_count); + gc->alloc_count = 0; +#endif + return Py_BuildValue("(iii)", gcstate->generations[0].count, gcstate->generations[1].count, gcstate->generations[2].count); } -static int -referrersvisit(PyObject* obj, PyObject *objs) -{ - Py_ssize_t i; - for (i = 0; i < PyTuple_GET_SIZE(objs); i++) - if (PyTuple_GET_ITEM(objs, i) == obj) - return 1; - return 0; -} +/*[clinic input] +gc.get_referrers -static int -gc_referrers_for(PyObject *objs, PyGC_Head *list, PyObject *resultlist) -{ - PyGC_Head *gc; - PyObject *obj; - traverseproc traverse; - for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(gc)) { - obj = FROM_GC(gc); - traverse = Py_TYPE(obj)->tp_traverse; - if (obj == objs || obj == resultlist) - continue; - if (traverse(obj, (visitproc)referrersvisit, objs)) { - if (PyList_Append(resultlist, obj) < 0) - return 0; /* error */ - } - } - return 1; /* no error */ -} + *objs as args: object -PyDoc_STRVAR(gc_get_referrers__doc__, -"get_referrers(*objs) -> list\n\ -Return the list of objects that directly refer to any of objs."); +Return the list of objects that directly refer to any of 'objs'. +[clinic start generated code]*/ static PyObject * -gc_get_referrers(PyObject *self, PyObject *args) +gc_get_referrers_impl(PyObject *module, PyObject *args) +/*[clinic end generated code: output=296a09587f6a86b5 input=bae96961b14a0922]*/ { if (PySys_Audit("gc.get_referrers", "(O)", args) < 0) { return NULL; } - PyObject *result = PyList_New(0); - if (!result) { - return NULL; - } - - GCState *gcstate = get_gc_state(); - for (int i = 0; i < NUM_GENERATIONS; i++) { - if (!(gc_referrers_for(args, GEN_HEAD(gcstate, i), result))) { - Py_DECREF(result); - return NULL; - } - } - return result; + PyInterpreterState *interp = _PyInterpreterState_GET(); + return _PyGC_GetReferrers(interp, args); } /* Append obj to list; return true if error (out of memory), false if OK. */ static int -referentsvisit(PyObject *obj, PyObject *list) +referentsvisit(PyObject *obj, void *arg) { + PyObject *list = arg; return PyList_Append(list, obj) < 0; } -PyDoc_STRVAR(gc_get_referents__doc__, -"get_referents(*objs) -> list\n\ -Return the list of objects that are directly referred to by objs."); +static int +append_referrents(PyObject *result, PyObject *args) +{ + for (Py_ssize_t i = 0; i < PyTuple_GET_SIZE(args); i++) { + PyObject *obj = PyTuple_GET_ITEM(args, i); + if (!_PyObject_IS_GC(obj)) { + continue; + } + + traverseproc traverse = Py_TYPE(obj)->tp_traverse; + if (!traverse) { + continue; + } + if (traverse(obj, referentsvisit, result)) { + return -1; + } + } + return 0; +} + +/*[clinic input] +gc.get_referents + + *objs as args: object + +Return the list of objects that are directly referred to by 'objs'. +[clinic start generated code]*/ static PyObject * -gc_get_referents(PyObject *self, PyObject *args) +gc_get_referents_impl(PyObject *module, PyObject *args) +/*[clinic end generated code: output=d47dc02cefd06fe8 input=b3ceab0c34038cbf]*/ { - Py_ssize_t i; if (PySys_Audit("gc.get_referents", "(O)", args) < 0) { return NULL; } + PyInterpreterState *interp = _PyInterpreterState_GET(); PyObject *result = PyList_New(0); if (result == NULL) return NULL; - for (i = 0; i < PyTuple_GET_SIZE(args); i++) { - traverseproc traverse; - PyObject *obj = PyTuple_GET_ITEM(args, i); + // NOTE: stop the world is a no-op in default build + _PyEval_StopTheWorld(interp); + int err = append_referrents(result, args); + _PyEval_StartTheWorld(interp); - if (!_PyObject_IS_GC(obj)) - continue; - traverse = Py_TYPE(obj)->tp_traverse; - if (! traverse) - continue; - if (traverse(obj, (visitproc)referentsvisit, result)) { - Py_DECREF(result); - return NULL; - } + if (err < 0) { + Py_CLEAR(result); } + return result; } @@ -1776,54 +313,25 @@ static PyObject * gc_get_objects_impl(PyObject *module, Py_ssize_t generation) /*[clinic end generated code: output=48b35fea4ba6cb0e input=ef7da9df9806754c]*/ { - PyThreadState *tstate = _PyThreadState_GET(); - int i; - PyObject* result; - GCState *gcstate = &tstate->interp->gc; - if (PySys_Audit("gc.get_objects", "n", generation) < 0) { return NULL; } - result = PyList_New(0); - if (result == NULL) { - return NULL; + if (generation >= NUM_GENERATIONS) { + return PyErr_Format(PyExc_ValueError, + "generation parameter must be less than the number of " + "available generations (%i)", + NUM_GENERATIONS); } - /* If generation is passed, we extract only that generation */ - if (generation != -1) { - if (generation >= NUM_GENERATIONS) { - _PyErr_Format(tstate, PyExc_ValueError, - "generation parameter must be less than the number of " - "available generations (%i)", - NUM_GENERATIONS); - goto error; - } - - if (generation < 0) { - _PyErr_SetString(tstate, PyExc_ValueError, - "generation parameter cannot be negative"); - goto error; - } - - if (append_objects(result, GEN_HEAD(gcstate, generation))) { - goto error; - } - - return result; - } - - /* If generation is not passed or None, get all objects from all generations */ - for (i = 0; i < NUM_GENERATIONS; i++) { - if (append_objects(result, GEN_HEAD(gcstate, i))) { - goto error; - } + if (generation < -1) { + PyErr_SetString(PyExc_ValueError, + "generation parameter cannot be negative"); + return NULL; } - return result; -error: - Py_DECREF(result); - return NULL; + PyInterpreterState *interp = _PyInterpreterState_GET(); + return _PyGC_GetObjects(interp, (int)generation); } /*[clinic input] @@ -1875,7 +383,7 @@ error: /*[clinic input] -gc.is_tracked +gc.is_tracked -> bool obj: object / @@ -1885,21 +393,15 @@ Returns true if the object is tracked by the garbage collector. Simple atomic objects will return false. [clinic start generated code]*/ -static PyObject * -gc_is_tracked(PyObject *module, PyObject *obj) -/*[clinic end generated code: output=14f0103423b28e31 input=d83057f170ea2723]*/ +static int +gc_is_tracked_impl(PyObject *module, PyObject *obj) +/*[clinic end generated code: output=91c8d086b7f47a33 input=423b98ec680c3126]*/ { - PyObject *result; - - if (_PyObject_IS_GC(obj) && _PyObject_GC_IS_TRACKED(obj)) - result = Py_True; - else - result = Py_False; - return Py_NewRef(result); + return PyObject_GC_IsTracked(obj); } /*[clinic input] -gc.is_finalized +gc.is_finalized -> bool obj: object / @@ -1907,14 +409,11 @@ gc.is_finalized Returns true if the object has been already finalized by the GC. [clinic start generated code]*/ -static PyObject * -gc_is_finalized(PyObject *module, PyObject *obj) -/*[clinic end generated code: output=e1516ac119a918ed input=201d0c58f69ae390]*/ +static int +gc_is_finalized_impl(PyObject *module, PyObject *obj) +/*[clinic end generated code: output=401ff5d6fc660429 input=ca4d111c8f8c4e3a]*/ { - if (_PyObject_IS_GC(obj) && _PyGCHead_FINALIZED(AS_GC(obj))) { - Py_RETURN_TRUE; - } - Py_RETURN_FALSE; + return PyObject_GC_IsFinalized(obj); } /*[clinic input] @@ -1931,11 +430,8 @@ static PyObject * gc_freeze_impl(PyObject *module) /*[clinic end generated code: output=502159d9cdc4c139 input=b602b16ac5febbe5]*/ { - GCState *gcstate = get_gc_state(); - for (int i = 0; i < NUM_GENERATIONS; ++i) { - gc_list_merge(GEN_HEAD(gcstate, i), &gcstate->permanent_generation.head); - gcstate->generations[i].count = 0; - } + PyInterpreterState *interp = _PyInterpreterState_GET(); + _PyGC_Freeze(interp); Py_RETURN_NONE; } @@ -1951,9 +447,8 @@ static PyObject * gc_unfreeze_impl(PyObject *module) /*[clinic end generated code: output=1c15f2043b25e169 input=2dd52b170f4cef6c]*/ { - GCState *gcstate = get_gc_state(); - gc_list_merge(&gcstate->permanent_generation.head, - GEN_HEAD(gcstate, NUM_GENERATIONS-1)); + PyInterpreterState *interp = _PyInterpreterState_GET(); + _PyGC_Unfreeze(interp); Py_RETURN_NONE; } @@ -1967,8 +462,8 @@ static Py_ssize_t gc_get_freeze_count_impl(PyObject *module) /*[clinic end generated code: output=61cbd9f43aa032e1 input=45ffbc65cfe2a6ed]*/ { - GCState *gcstate = get_gc_state(); - return gc_list_size(&gcstate->permanent_generation.head); + PyInterpreterState *interp = _PyInterpreterState_GET(); + return _PyGC_GetFreezeCount(interp); } @@ -1984,7 +479,7 @@ PyDoc_STRVAR(gc__doc__, "set_debug() -- Set debugging flags.\n" "get_debug() -- Get debugging flags.\n" "set_threshold() -- Set the collection thresholds.\n" -"get_threshold() -- Return the current the collection thresholds.\n" +"get_threshold() -- Return the current collection thresholds.\n" "get_objects() -- Return a list of all objects tracked by the collector.\n" "is_tracked() -- Returns true if a given object is tracked.\n" "is_finalized() -- Returns true if a given object has been already finalized.\n" @@ -2001,17 +496,15 @@ static PyMethodDef GcMethods[] = { GC_SET_DEBUG_METHODDEF GC_GET_DEBUG_METHODDEF GC_GET_COUNT_METHODDEF - {"set_threshold", gc_set_threshold, METH_VARARGS, gc_set_thresh__doc__}, + GC_SET_THRESHOLD_METHODDEF GC_GET_THRESHOLD_METHODDEF GC_COLLECT_METHODDEF GC_GET_OBJECTS_METHODDEF GC_GET_STATS_METHODDEF GC_IS_TRACKED_METHODDEF GC_IS_FINALIZED_METHODDEF - {"get_referrers", gc_get_referrers, METH_VARARGS, - gc_get_referrers__doc__}, - {"get_referents", gc_get_referents, METH_VARARGS, - gc_get_referents__doc__}, + GC_GET_REFERRERS_METHODDEF + GC_GET_REFERENTS_METHODDEF GC_FREEZE_METHODDEF GC_UNFREEZE_METHODDEF GC_GET_FREEZE_COUNT_METHODDEF @@ -2034,7 +527,7 @@ gcmodule_exec(PyObject *module) return -1; } -#define ADD_INT(NAME) if (PyModule_AddIntConstant(module, #NAME, NAME) < 0) { return -1; } +#define ADD_INT(NAME) if (PyModule_AddIntConstant(module, #NAME, _PyGC_ ## NAME) < 0) { return -1; } ADD_INT(DEBUG_STATS); ADD_INT(DEBUG_COLLECTABLE); ADD_INT(DEBUG_UNCOLLECTABLE); @@ -2047,6 +540,7 @@ gcmodule_exec(PyObject *module) static PyModuleDef_Slot gcmodule_slots[] = { {Py_mod_exec, gcmodule_exec}, {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED}, + {Py_mod_gil, Py_MOD_GIL_NOT_USED}, {0, NULL} }; @@ -2064,407 +558,3 @@ PyInit_gc(void) { return PyModuleDef_Init(&gcmodule); } - -/* C API for controlling the state of the garbage collector */ -int -PyGC_Enable(void) -{ - GCState *gcstate = get_gc_state(); - int old_state = gcstate->enabled; - gcstate->enabled = 1; - return old_state; -} - -int -PyGC_Disable(void) -{ - GCState *gcstate = get_gc_state(); - int old_state = gcstate->enabled; - gcstate->enabled = 0; - return old_state; -} - -int -PyGC_IsEnabled(void) -{ - GCState *gcstate = get_gc_state(); - return gcstate->enabled; -} - -/* Public API to invoke gc.collect() from C */ -Py_ssize_t -PyGC_Collect(void) -{ - PyThreadState *tstate = _PyThreadState_GET(); - GCState *gcstate = &tstate->interp->gc; - - if (!gcstate->enabled) { - return 0; - } - - Py_ssize_t n; - if (gcstate->collecting) { - /* already collecting, don't do anything */ - n = 0; - } - else { - gcstate->collecting = 1; - PyObject *exc = _PyErr_GetRaisedException(tstate); - n = gc_collect_with_callback(tstate, NUM_GENERATIONS - 1); - _PyErr_SetRaisedException(tstate, exc); - gcstate->collecting = 0; - } - - return n; -} - -Py_ssize_t -_PyGC_CollectNoFail(PyThreadState *tstate) -{ - /* Ideally, this function is only called on interpreter shutdown, - and therefore not recursively. Unfortunately, when there are daemon - threads, a daemon thread can start a cyclic garbage collection - during interpreter shutdown (and then never finish it). - See http://bugs.python.org/issue8713#msg195178 for an example. - */ - GCState *gcstate = &tstate->interp->gc; - if (gcstate->collecting) { - return 0; - } - - Py_ssize_t n; - gcstate->collecting = 1; - n = gc_collect_main(tstate, NUM_GENERATIONS - 1, NULL, NULL, 1); - gcstate->collecting = 0; - return n; -} - -void -_PyGC_DumpShutdownStats(PyInterpreterState *interp) -{ - GCState *gcstate = &interp->gc; - if (!(gcstate->debug & DEBUG_SAVEALL) - && gcstate->garbage != NULL && PyList_GET_SIZE(gcstate->garbage) > 0) { - const char *message; - if (gcstate->debug & DEBUG_UNCOLLECTABLE) - message = "gc: %zd uncollectable objects at " \ - "shutdown"; - else - message = "gc: %zd uncollectable objects at " \ - "shutdown; use gc.set_debug(gc.DEBUG_UNCOLLECTABLE) to list them"; - /* PyErr_WarnFormat does too many things and we are at shutdown, - the warnings module's dependencies (e.g. linecache) may be gone - already. */ - if (PyErr_WarnExplicitFormat(PyExc_ResourceWarning, "gc", 0, - "gc", NULL, message, - PyList_GET_SIZE(gcstate->garbage))) - PyErr_WriteUnraisable(NULL); - if (gcstate->debug & DEBUG_UNCOLLECTABLE) { - PyObject *repr = NULL, *bytes = NULL; - repr = PyObject_Repr(gcstate->garbage); - if (!repr || !(bytes = PyUnicode_EncodeFSDefault(repr))) - PyErr_WriteUnraisable(gcstate->garbage); - else { - PySys_WriteStderr( - " %s\n", - PyBytes_AS_STRING(bytes) - ); - } - Py_XDECREF(repr); - Py_XDECREF(bytes); - } - } -} - -static void -finalize_unlink_gc_head(PyGC_Head *gc) { - PyGC_Head *prev = GC_PREV(gc); - PyGC_Head *next = GC_NEXT(gc); - _PyGCHead_SET_NEXT(prev, next); - _PyGCHead_SET_PREV(next, prev); -} - -void -_PyGC_Fini(PyInterpreterState *interp) -{ - GCState *gcstate = &interp->gc; - Py_CLEAR(gcstate->garbage); - Py_CLEAR(gcstate->callbacks); - - /* Prevent a subtle bug that affects sub-interpreters that use basic - * single-phase init extensions (m_size == -1). Those extensions cause objects - * to be shared between interpreters, via the PyDict_Update(mdict, m_copy) call - * in import_find_extension(). - * - * If they are GC objects, their GC head next or prev links could refer to - * the interpreter _gc_runtime_state PyGC_Head nodes. Those nodes go away - * when the interpreter structure is freed and so pointers to them become - * invalid. If those objects are still used by another interpreter and - * UNTRACK is called on them, a crash will happen. We untrack the nodes - * here to avoid that. - * - * This bug was originally fixed when reported as gh-90228. The bug was - * re-introduced in gh-94673. - */ - for (int i = 0; i < NUM_GENERATIONS; i++) { - finalize_unlink_gc_head(&gcstate->generations[i].head); - } - finalize_unlink_gc_head(&gcstate->permanent_generation.head); -} - -/* for debugging */ -void -_PyGC_Dump(PyGC_Head *g) -{ - _PyObject_Dump(FROM_GC(g)); -} - - -#ifdef Py_DEBUG -static int -visit_validate(PyObject *op, void *parent_raw) -{ - PyObject *parent = _PyObject_CAST(parent_raw); - if (_PyObject_IsFreed(op)) { - _PyObject_ASSERT_FAILED_MSG(parent, - "PyObject_GC_Track() object is not valid"); - } - return 0; -} -#endif - - -/* extension modules might be compiled with GC support so these - functions must always be available */ - -void -PyObject_GC_Track(void *op_raw) -{ - PyObject *op = _PyObject_CAST(op_raw); - if (_PyObject_GC_IS_TRACKED(op)) { - _PyObject_ASSERT_FAILED_MSG(op, - "object already tracked " - "by the garbage collector"); - } - _PyObject_GC_TRACK(op); - -#ifdef Py_DEBUG - /* Check that the object is valid: validate objects traversed - by tp_traverse() */ - traverseproc traverse = Py_TYPE(op)->tp_traverse; - (void)traverse(op, visit_validate, op); -#endif -} - -void -PyObject_GC_UnTrack(void *op_raw) -{ - PyObject *op = _PyObject_CAST(op_raw); - /* Obscure: the Py_TRASHCAN mechanism requires that we be able to - * call PyObject_GC_UnTrack twice on an object. - */ - if (_PyObject_GC_IS_TRACKED(op)) { - _PyObject_GC_UNTRACK(op); - } -} - -int -PyObject_IS_GC(PyObject *obj) -{ - return _PyObject_IS_GC(obj); -} - -void -_Py_ScheduleGC(PyInterpreterState *interp) -{ - GCState *gcstate = &interp->gc; - if (gcstate->collecting == 1) { - return; - } - struct _ceval_state *ceval = &interp->ceval; - if (!_Py_atomic_load_relaxed(&ceval->gc_scheduled)) { - _Py_atomic_store_relaxed(&ceval->gc_scheduled, 1); - _Py_atomic_store_relaxed(&ceval->eval_breaker, 1); - } -} - -void -_PyObject_GC_Link(PyObject *op) -{ - PyGC_Head *g = AS_GC(op); - assert(((uintptr_t)g & (sizeof(uintptr_t)-1)) == 0); // g must be correctly aligned - - PyThreadState *tstate = _PyThreadState_GET(); - GCState *gcstate = &tstate->interp->gc; - g->_gc_next = 0; - g->_gc_prev = 0; - gcstate->generations[0].count++; /* number of allocated GC objects */ - if (gcstate->generations[0].count > gcstate->generations[0].threshold && - gcstate->enabled && - gcstate->generations[0].threshold && - !gcstate->collecting && - !_PyErr_Occurred(tstate)) - { - _Py_ScheduleGC(tstate->interp); - } -} - -void -_Py_RunGC(PyThreadState *tstate) -{ - GCState *gcstate = &tstate->interp->gc; - if (!gcstate->enabled) { - return; - } - gcstate->collecting = 1; - gc_collect_generations(tstate); - gcstate->collecting = 0; -} - -static PyObject * -gc_alloc(size_t basicsize, size_t presize) -{ - PyThreadState *tstate = _PyThreadState_GET(); - if (basicsize > PY_SSIZE_T_MAX - presize) { - return _PyErr_NoMemory(tstate); - } - size_t size = presize + basicsize; - char *mem = PyObject_Malloc(size); - if (mem == NULL) { - return _PyErr_NoMemory(tstate); - } - ((PyObject **)mem)[0] = NULL; - ((PyObject **)mem)[1] = NULL; - PyObject *op = (PyObject *)(mem + presize); - _PyObject_GC_Link(op); - return op; -} - -PyObject * -_PyObject_GC_New(PyTypeObject *tp) -{ - size_t presize = _PyType_PreHeaderSize(tp); - PyObject *op = gc_alloc(_PyObject_SIZE(tp), presize); - if (op == NULL) { - return NULL; - } - _PyObject_Init(op, tp); - return op; -} - -PyVarObject * -_PyObject_GC_NewVar(PyTypeObject *tp, Py_ssize_t nitems) -{ - PyVarObject *op; - - if (nitems < 0) { - PyErr_BadInternalCall(); - return NULL; - } - size_t presize = _PyType_PreHeaderSize(tp); - size_t size = _PyObject_VAR_SIZE(tp, nitems); - op = (PyVarObject *)gc_alloc(size, presize); - if (op == NULL) { - return NULL; - } - _PyObject_InitVar(op, tp, nitems); - return op; -} - -PyObject * -PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *tp, size_t extra_size) -{ - size_t presize = _PyType_PreHeaderSize(tp); - PyObject *op = gc_alloc(_PyObject_SIZE(tp) + extra_size, presize); - if (op == NULL) { - return NULL; - } - memset(op, 0, _PyObject_SIZE(tp) + extra_size); - _PyObject_Init(op, tp); - return op; -} - -PyVarObject * -_PyObject_GC_Resize(PyVarObject *op, Py_ssize_t nitems) -{ - const size_t basicsize = _PyObject_VAR_SIZE(Py_TYPE(op), nitems); - const size_t presize = _PyType_PreHeaderSize(((PyObject *)op)->ob_type); - _PyObject_ASSERT((PyObject *)op, !_PyObject_GC_IS_TRACKED(op)); - if (basicsize > (size_t)PY_SSIZE_T_MAX - presize) { - return (PyVarObject *)PyErr_NoMemory(); - } - char *mem = (char *)op - presize; - mem = (char *)PyObject_Realloc(mem, presize + basicsize); - if (mem == NULL) { - return (PyVarObject *)PyErr_NoMemory(); - } - op = (PyVarObject *) (mem + presize); - Py_SET_SIZE(op, nitems); - return op; -} - -void -PyObject_GC_Del(void *op) -{ - size_t presize = _PyType_PreHeaderSize(((PyObject *)op)->ob_type); - PyGC_Head *g = AS_GC(op); - if (_PyObject_GC_IS_TRACKED(op)) { - gc_list_remove(g); -#ifdef Py_DEBUG - PyObject *exc = PyErr_GetRaisedException(); - if (PyErr_WarnExplicitFormat(PyExc_ResourceWarning, "gc", 0, - "gc", NULL, "Object of type %s is not untracked before destruction", - ((PyObject*)op)->ob_type->tp_name)) { - PyErr_WriteUnraisable(NULL); - } - PyErr_SetRaisedException(exc); -#endif - } - GCState *gcstate = get_gc_state(); - if (gcstate->generations[0].count > 0) { - gcstate->generations[0].count--; - } - PyObject_Free(((char *)op)-presize); -} - -int -PyObject_GC_IsTracked(PyObject* obj) -{ - if (_PyObject_IS_GC(obj) && _PyObject_GC_IS_TRACKED(obj)) { - return 1; - } - return 0; -} - -int -PyObject_GC_IsFinalized(PyObject *obj) -{ - if (_PyObject_IS_GC(obj) && _PyGCHead_FINALIZED(AS_GC(obj))) { - return 1; - } - return 0; -} - -void -PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void *arg) -{ - size_t i; - GCState *gcstate = get_gc_state(); - int origenstate = gcstate->enabled; - gcstate->enabled = 0; - for (i = 0; i < NUM_GENERATIONS; i++) { - PyGC_Head *gc_list, *gc; - gc_list = GEN_HEAD(gcstate, i); - for (gc = GC_NEXT(gc_list); gc != gc_list; gc = GC_NEXT(gc)) { - PyObject *op = FROM_GC(gc); - Py_INCREF(op); - int res = callback(op, arg); - Py_DECREF(op); - if (!res) { - goto done; - } - } - } -done: - gcstate->enabled = origenstate; -} |