mirror of
https://github.com/python/cpython
synced 2024-09-15 23:57:10 +00:00
e69d068ad0
The `_PyThreadState_Bind()` function is called before the first `PyEval_AcquireThread()` so it's not synchronized with the stop the world GC. We had a race where `gc_visit_heaps()` might visit a thread's heap while it's being initialized. Use a simple atomic int to avoid visiting heaps for threads that are not yet fully initialized (i.e., before `tstate_mimalloc_bind()` is called). The race was reproducible by running: `python Lib/test/test_importlib/partial/pool_in_threads.py`.
1854 lines
53 KiB
C
1854 lines
53 KiB
C
// Cyclic garbage collector implementation for free-threaded build.
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#include "Python.h"
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#include "pycore_brc.h" // struct _brc_thread_state
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#include "pycore_ceval.h" // _Py_set_eval_breaker_bit()
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#include "pycore_context.h"
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#include "pycore_dict.h" // _PyDict_MaybeUntrack()
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#include "pycore_initconfig.h"
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#include "pycore_interp.h" // PyInterpreterState.gc
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#include "pycore_object.h"
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#include "pycore_object_alloc.h" // _PyObject_MallocWithType()
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#include "pycore_object_stack.h"
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#include "pycore_pyerrors.h"
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#include "pycore_pystate.h" // _PyThreadState_GET()
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#include "pycore_tstate.h" // _PyThreadStateImpl
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#include "pycore_weakref.h" // _PyWeakref_ClearRef()
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#include "pydtrace.h"
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#ifdef Py_GIL_DISABLED
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typedef struct _gc_runtime_state GCState;
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#ifdef Py_DEBUG
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# define GC_DEBUG
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#endif
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// Each thread buffers the count of allocated objects in a thread-local
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// variable up to +/- this amount to reduce the overhead of updating
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// the global count.
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#define LOCAL_ALLOC_COUNT_THRESHOLD 512
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// Automatically choose the generation that needs collecting.
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#define GENERATION_AUTO (-1)
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// A linked list of objects using the `ob_tid` field as the next pointer.
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// The linked list pointers are distinct from any real thread ids, because the
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// thread ids returned by _Py_ThreadId() are also pointers to distinct objects.
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// No thread will confuse its own id with a linked list pointer.
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struct worklist {
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uintptr_t head;
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};
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struct worklist_iter {
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uintptr_t *ptr; // pointer to current object
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uintptr_t *next; // next value of ptr
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};
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struct visitor_args {
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size_t offset; // offset of PyObject from start of block
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};
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// Per-collection state
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struct collection_state {
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struct visitor_args base;
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PyInterpreterState *interp;
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GCState *gcstate;
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Py_ssize_t collected;
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Py_ssize_t uncollectable;
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Py_ssize_t long_lived_total;
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struct worklist unreachable;
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struct worklist legacy_finalizers;
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struct worklist wrcb_to_call;
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struct worklist objs_to_decref;
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};
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// iterate over a worklist
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#define WORKSTACK_FOR_EACH(stack, op) \
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for ((op) = (PyObject *)(stack)->head; (op) != NULL; (op) = (PyObject *)(op)->ob_tid)
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// iterate over a worklist with support for removing the current object
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#define WORKSTACK_FOR_EACH_ITER(stack, iter, op) \
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for (worklist_iter_init((iter), &(stack)->head), (op) = (PyObject *)(*(iter)->ptr); \
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(op) != NULL; \
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worklist_iter_init((iter), (iter)->next), (op) = (PyObject *)(*(iter)->ptr))
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static void
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worklist_push(struct worklist *worklist, PyObject *op)
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{
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assert(op->ob_tid == 0);
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op->ob_tid = worklist->head;
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worklist->head = (uintptr_t)op;
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}
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static PyObject *
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worklist_pop(struct worklist *worklist)
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{
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PyObject *op = (PyObject *)worklist->head;
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if (op != NULL) {
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worklist->head = op->ob_tid;
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_Py_atomic_store_uintptr_relaxed(&op->ob_tid, 0);
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}
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return op;
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}
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static void
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worklist_iter_init(struct worklist_iter *iter, uintptr_t *next)
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{
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iter->ptr = next;
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PyObject *op = (PyObject *)*(iter->ptr);
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if (op) {
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iter->next = &op->ob_tid;
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}
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}
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static void
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worklist_remove(struct worklist_iter *iter)
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{
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PyObject *op = (PyObject *)*(iter->ptr);
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*(iter->ptr) = op->ob_tid;
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op->ob_tid = 0;
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iter->next = iter->ptr;
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}
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static inline int
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gc_is_unreachable(PyObject *op)
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{
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return (op->ob_gc_bits & _PyGC_BITS_UNREACHABLE) != 0;
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}
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static void
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gc_set_unreachable(PyObject *op)
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{
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op->ob_gc_bits |= _PyGC_BITS_UNREACHABLE;
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}
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static void
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gc_clear_unreachable(PyObject *op)
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{
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op->ob_gc_bits &= ~_PyGC_BITS_UNREACHABLE;
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}
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// Initialize the `ob_tid` field to zero if the object is not already
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// initialized as unreachable.
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static void
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gc_maybe_init_refs(PyObject *op)
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{
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if (!gc_is_unreachable(op)) {
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gc_set_unreachable(op);
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op->ob_tid = 0;
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}
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}
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static inline Py_ssize_t
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gc_get_refs(PyObject *op)
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{
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return (Py_ssize_t)op->ob_tid;
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}
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static inline void
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gc_add_refs(PyObject *op, Py_ssize_t refs)
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{
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assert(_PyObject_GC_IS_TRACKED(op));
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op->ob_tid += refs;
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}
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static inline void
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gc_decref(PyObject *op)
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{
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op->ob_tid -= 1;
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}
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static void
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disable_deferred_refcounting(PyObject *op)
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{
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if (_PyObject_HasDeferredRefcount(op)) {
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op->ob_gc_bits &= ~_PyGC_BITS_DEFERRED;
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op->ob_ref_shared -= (1 << _Py_REF_SHARED_SHIFT);
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}
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}
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static Py_ssize_t
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merge_refcount(PyObject *op, Py_ssize_t extra)
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{
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assert(_PyInterpreterState_GET()->stoptheworld.world_stopped);
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Py_ssize_t refcount = Py_REFCNT(op);
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refcount += extra;
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#ifdef Py_REF_DEBUG
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_Py_AddRefTotal(_PyThreadState_GET(), extra);
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#endif
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// No atomics necessary; all other threads in this interpreter are paused.
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op->ob_tid = 0;
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op->ob_ref_local = 0;
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op->ob_ref_shared = _Py_REF_SHARED(refcount, _Py_REF_MERGED);
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return refcount;
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}
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static void
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gc_restore_tid(PyObject *op)
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{
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assert(_PyInterpreterState_GET()->stoptheworld.world_stopped);
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mi_segment_t *segment = _mi_ptr_segment(op);
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if (_Py_REF_IS_MERGED(op->ob_ref_shared)) {
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op->ob_tid = 0;
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}
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else {
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// NOTE: may change ob_tid if the object was re-initialized by
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// a different thread or its segment was abandoned and reclaimed.
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// The segment thread id might be zero, in which case we should
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// ensure the refcounts are now merged.
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op->ob_tid = segment->thread_id;
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if (op->ob_tid == 0) {
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merge_refcount(op, 0);
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}
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}
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}
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static void
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gc_restore_refs(PyObject *op)
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{
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if (gc_is_unreachable(op)) {
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gc_restore_tid(op);
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gc_clear_unreachable(op);
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}
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}
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// Given a mimalloc memory block return the PyObject stored in it or NULL if
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// the block is not allocated or the object is not tracked or is immortal.
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static PyObject *
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op_from_block(void *block, void *arg, bool include_frozen)
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{
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struct visitor_args *a = arg;
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if (block == NULL) {
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return NULL;
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}
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PyObject *op = (PyObject *)((char*)block + a->offset);
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assert(PyObject_IS_GC(op));
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if (!_PyObject_GC_IS_TRACKED(op)) {
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return NULL;
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}
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if (!include_frozen && (op->ob_gc_bits & _PyGC_BITS_FROZEN) != 0) {
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return NULL;
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}
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return op;
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}
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static int
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gc_visit_heaps_lock_held(PyInterpreterState *interp, mi_block_visit_fun *visitor,
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struct visitor_args *arg)
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{
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// Offset of PyObject header from start of memory block.
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Py_ssize_t offset_base = 0;
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if (_PyMem_DebugEnabled()) {
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// The debug allocator adds two words at the beginning of each block.
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offset_base += 2 * sizeof(size_t);
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}
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// Objects with Py_TPFLAGS_PREHEADER have two extra fields
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Py_ssize_t offset_pre = offset_base + 2 * sizeof(PyObject*);
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// visit each thread's heaps for GC objects
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for (PyThreadState *p = interp->threads.head; p != NULL; p = p->next) {
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struct _mimalloc_thread_state *m = &((_PyThreadStateImpl *)p)->mimalloc;
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if (!_Py_atomic_load_int(&m->initialized)) {
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// The thread may not have called tstate_mimalloc_bind() yet.
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continue;
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}
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arg->offset = offset_base;
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if (!mi_heap_visit_blocks(&m->heaps[_Py_MIMALLOC_HEAP_GC], true,
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visitor, arg)) {
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return -1;
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}
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arg->offset = offset_pre;
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if (!mi_heap_visit_blocks(&m->heaps[_Py_MIMALLOC_HEAP_GC_PRE], true,
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visitor, arg)) {
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return -1;
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}
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}
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// visit blocks in the per-interpreter abandoned pool (from dead threads)
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mi_abandoned_pool_t *pool = &interp->mimalloc.abandoned_pool;
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arg->offset = offset_base;
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if (!_mi_abandoned_pool_visit_blocks(pool, _Py_MIMALLOC_HEAP_GC, true,
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visitor, arg)) {
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return -1;
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}
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arg->offset = offset_pre;
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if (!_mi_abandoned_pool_visit_blocks(pool, _Py_MIMALLOC_HEAP_GC_PRE, true,
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visitor, arg)) {
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return -1;
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}
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return 0;
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}
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// Visits all GC objects in the interpreter's heaps.
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// NOTE: It is not safe to allocate or free any mimalloc managed memory while
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// this function is running.
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static int
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gc_visit_heaps(PyInterpreterState *interp, mi_block_visit_fun *visitor,
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struct visitor_args *arg)
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{
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// Other threads in the interpreter must be paused so that we can safely
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// traverse their heaps.
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assert(interp->stoptheworld.world_stopped);
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int err;
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HEAD_LOCK(&_PyRuntime);
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err = gc_visit_heaps_lock_held(interp, visitor, arg);
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HEAD_UNLOCK(&_PyRuntime);
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return err;
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}
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static void
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merge_queued_objects(_PyThreadStateImpl *tstate, struct collection_state *state)
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{
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struct _brc_thread_state *brc = &tstate->brc;
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_PyObjectStack_Merge(&brc->local_objects_to_merge, &brc->objects_to_merge);
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PyObject *op;
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while ((op = _PyObjectStack_Pop(&brc->local_objects_to_merge)) != NULL) {
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// Subtract one when merging because the queue had a reference.
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Py_ssize_t refcount = merge_refcount(op, -1);
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if (!_PyObject_GC_IS_TRACKED(op) && refcount == 0) {
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// GC objects with zero refcount are handled subsequently by the
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// GC as if they were cyclic trash, but we have to handle dead
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// non-GC objects here. Add one to the refcount so that we can
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// decref and deallocate the object once we start the world again.
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op->ob_ref_shared += (1 << _Py_REF_SHARED_SHIFT);
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#ifdef Py_REF_DEBUG
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_Py_IncRefTotal(_PyThreadState_GET());
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#endif
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worklist_push(&state->objs_to_decref, op);
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}
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}
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}
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static void
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merge_all_queued_objects(PyInterpreterState *interp, struct collection_state *state)
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{
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HEAD_LOCK(&_PyRuntime);
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for (PyThreadState *p = interp->threads.head; p != NULL; p = p->next) {
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merge_queued_objects((_PyThreadStateImpl *)p, state);
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}
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HEAD_UNLOCK(&_PyRuntime);
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}
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static void
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process_delayed_frees(PyInterpreterState *interp)
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{
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// In STW status, we can observe the latest write sequence by
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// advancing the write sequence immediately.
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_Py_qsbr_advance(&interp->qsbr);
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_PyThreadStateImpl *current_tstate = (_PyThreadStateImpl *)_PyThreadState_GET();
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_Py_qsbr_quiescent_state(current_tstate->qsbr);
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HEAD_LOCK(&_PyRuntime);
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PyThreadState *tstate = interp->threads.head;
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while (tstate != NULL) {
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_PyMem_ProcessDelayed(tstate);
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tstate = (PyThreadState *)tstate->next;
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}
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HEAD_UNLOCK(&_PyRuntime);
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}
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// Subtract an incoming reference from the computed "gc_refs" refcount.
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static int
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visit_decref(PyObject *op, void *arg)
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{
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if (_PyObject_GC_IS_TRACKED(op) && !_Py_IsImmortal(op)) {
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// If update_refs hasn't reached this object yet, mark it
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// as (tentatively) unreachable and initialize ob_tid to zero.
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gc_maybe_init_refs(op);
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gc_decref(op);
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}
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return 0;
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}
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// Compute the number of external references to objects in the heap
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// by subtracting internal references from the refcount. The difference is
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// computed in the ob_tid field (we restore it later).
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static bool
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update_refs(const mi_heap_t *heap, const mi_heap_area_t *area,
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void *block, size_t block_size, void *args)
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{
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PyObject *op = op_from_block(block, args, false);
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if (op == NULL) {
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return true;
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}
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// Exclude immortal objects from garbage collection
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if (_Py_IsImmortal(op)) {
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op->ob_tid = 0;
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_PyObject_GC_UNTRACK(op);
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gc_clear_unreachable(op);
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return true;
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}
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Py_ssize_t refcount = Py_REFCNT(op);
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refcount -= _PyObject_HasDeferredRefcount(op);
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_PyObject_ASSERT(op, refcount >= 0);
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if (refcount > 0 && !_PyObject_HasDeferredRefcount(op)) {
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// Untrack tuples and dicts as necessary in this pass, but not objects
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// with zero refcount, which we will want to collect.
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if (PyTuple_CheckExact(op)) {
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_PyTuple_MaybeUntrack(op);
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if (!_PyObject_GC_IS_TRACKED(op)) {
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gc_restore_refs(op);
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return true;
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}
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}
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else if (PyDict_CheckExact(op)) {
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_PyDict_MaybeUntrack(op);
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if (!_PyObject_GC_IS_TRACKED(op)) {
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gc_restore_refs(op);
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return true;
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}
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}
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}
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// We repurpose ob_tid to compute "gc_refs", the number of external
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// references to the object (i.e., from outside the GC heaps). This means
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// that ob_tid is no longer a valid thread id until it is restored by
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// scan_heap_visitor(). Until then, we cannot use the standard reference
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// counting functions or allow other threads to run Python code.
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gc_maybe_init_refs(op);
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// Add the actual refcount to ob_tid.
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gc_add_refs(op, refcount);
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// Subtract internal references from ob_tid. Objects with ob_tid > 0
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// are directly reachable from outside containers, and so can't be
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// collected.
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Py_TYPE(op)->tp_traverse(op, visit_decref, NULL);
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return true;
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}
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static int
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visit_clear_unreachable(PyObject *op, _PyObjectStack *stack)
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{
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if (gc_is_unreachable(op)) {
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_PyObject_ASSERT(op, _PyObject_GC_IS_TRACKED(op));
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gc_clear_unreachable(op);
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return _PyObjectStack_Push(stack, op);
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}
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return 0;
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}
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// Transitively clear the unreachable bit on all objects reachable from op.
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static int
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mark_reachable(PyObject *op)
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{
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_PyObjectStack stack = { NULL };
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do {
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traverseproc traverse = Py_TYPE(op)->tp_traverse;
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if (traverse(op, (visitproc)&visit_clear_unreachable, &stack) < 0) {
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_PyObjectStack_Clear(&stack);
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return -1;
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}
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op = _PyObjectStack_Pop(&stack);
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} while (op != NULL);
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return 0;
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}
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#ifdef GC_DEBUG
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static bool
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validate_gc_objects(const mi_heap_t *heap, const mi_heap_area_t *area,
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void *block, size_t block_size, void *args)
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{
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PyObject *op = op_from_block(block, args, false);
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if (op == NULL) {
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return true;
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}
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_PyObject_ASSERT(op, gc_is_unreachable(op));
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_PyObject_ASSERT_WITH_MSG(op, gc_get_refs(op) >= 0,
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"refcount is too small");
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return true;
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}
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#endif
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static bool
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mark_heap_visitor(const mi_heap_t *heap, const mi_heap_area_t *area,
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void *block, size_t block_size, void *args)
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{
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PyObject *op = op_from_block(block, args, false);
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if (op == NULL) {
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return true;
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}
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_PyObject_ASSERT_WITH_MSG(op, gc_get_refs(op) >= 0,
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"refcount is too small");
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if (gc_is_unreachable(op) && gc_get_refs(op) != 0) {
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// Object is reachable but currently marked as unreachable.
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// Mark it as reachable and traverse its pointers to find
|
|
// any other object that may be directly reachable from it.
|
|
gc_clear_unreachable(op);
|
|
|
|
// Transitively mark reachable objects by clearing the unreachable flag.
|
|
if (mark_reachable(op) < 0) {
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
static bool
|
|
scan_heap_visitor(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, false);
|
|
if (op == NULL) {
|
|
return true;
|
|
}
|
|
|
|
struct collection_state *state = (struct collection_state *)args;
|
|
if (gc_is_unreachable(op)) {
|
|
// Disable deferred refcounting for unreachable objects so that they
|
|
// are collected immediately after finalization.
|
|
disable_deferred_refcounting(op);
|
|
|
|
// Merge and add one to the refcount to prevent deallocation while we
|
|
// are holding on to it in a worklist.
|
|
merge_refcount(op, 1);
|
|
|
|
if (has_legacy_finalizer(op)) {
|
|
// would be unreachable, but has legacy finalizer
|
|
gc_clear_unreachable(op);
|
|
worklist_push(&state->legacy_finalizers, op);
|
|
}
|
|
else {
|
|
worklist_push(&state->unreachable, op);
|
|
}
|
|
}
|
|
else {
|
|
// object is reachable, restore `ob_tid`; we're done with these objects
|
|
gc_restore_tid(op);
|
|
state->long_lived_total++;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
static int
|
|
move_legacy_finalizer_reachable(struct collection_state *state);
|
|
|
|
static int
|
|
deduce_unreachable_heap(PyInterpreterState *interp,
|
|
struct collection_state *state)
|
|
{
|
|
// Identify objects that are directly reachable from outside the GC heap
|
|
// by computing the difference between the refcount and the number of
|
|
// incoming references.
|
|
gc_visit_heaps(interp, &update_refs, &state->base);
|
|
|
|
#ifdef GC_DEBUG
|
|
// Check that all objects are marked as unreachable and that the computed
|
|
// reference count difference (stored in `ob_tid`) is non-negative.
|
|
gc_visit_heaps(interp, &validate_gc_objects, &state->base);
|
|
#endif
|
|
|
|
// Transitively mark reachable objects by clearing the
|
|
// _PyGC_BITS_UNREACHABLE flag.
|
|
if (gc_visit_heaps(interp, &mark_heap_visitor, &state->base) < 0) {
|
|
return -1;
|
|
}
|
|
|
|
// Identify remaining unreachable objects and push them onto a stack.
|
|
// Restores ob_tid for reachable objects.
|
|
gc_visit_heaps(interp, &scan_heap_visitor, &state->base);
|
|
|
|
if (state->legacy_finalizers.head) {
|
|
// There may be objects reachable from legacy finalizers that are in
|
|
// the unreachable set. We need to mark them as reachable.
|
|
if (move_legacy_finalizer_reachable(state) < 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
move_legacy_finalizer_reachable(struct collection_state *state)
|
|
{
|
|
// Clear the reachable bit on all objects transitively reachable
|
|
// from the objects with legacy finalizers.
|
|
PyObject *op;
|
|
WORKSTACK_FOR_EACH(&state->legacy_finalizers, op) {
|
|
if (mark_reachable(op) < 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
// Move the reachable objects from the unreachable worklist to the legacy
|
|
// finalizer worklist.
|
|
struct worklist_iter iter;
|
|
WORKSTACK_FOR_EACH_ITER(&state->unreachable, &iter, op) {
|
|
if (!gc_is_unreachable(op)) {
|
|
worklist_remove(&iter);
|
|
worklist_push(&state->legacy_finalizers, op);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
// Clear all weakrefs to unreachable objects. Weakrefs with callbacks are
|
|
// enqueued in `wrcb_to_call`, but not invoked yet.
|
|
static void
|
|
clear_weakrefs(struct collection_state *state)
|
|
{
|
|
PyObject *op;
|
|
WORKSTACK_FOR_EACH(&state->unreachable, op) {
|
|
if (PyWeakref_Check(op)) {
|
|
// Clear weakrefs that are themselves unreachable to ensure their
|
|
// callbacks will not be executed later from a `tp_clear()`
|
|
// inside delete_garbage(). That would be unsafe: it could
|
|
// resurrect a dead object or access a an already cleared object.
|
|
// See bpo-38006 for one example.
|
|
_PyWeakref_ClearRef((PyWeakReference *)op);
|
|
}
|
|
|
|
if (!_PyType_SUPPORTS_WEAKREFS(Py_TYPE(op))) {
|
|
continue;
|
|
}
|
|
|
|
// NOTE: This is never triggered for static types so we can avoid the
|
|
// (slightly) more costly _PyObject_GET_WEAKREFS_LISTPTR().
|
|
PyWeakReference **wrlist = _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(op);
|
|
|
|
// `op` may have some weakrefs. March over the list, clear
|
|
// all the weakrefs, and enqueue the weakrefs with callbacks
|
|
// that must be called into wrcb_to_call.
|
|
for (PyWeakReference *wr = *wrlist; wr != NULL; wr = *wrlist) {
|
|
// _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);
|
|
|
|
// We do not invoke callbacks for weakrefs that are themselves
|
|
// unreachable. This is partly for historical reasons: weakrefs
|
|
// predate safe object finalization, and a weakref that is itself
|
|
// unreachable may have a callback that resurrects other
|
|
// unreachable objects.
|
|
if (wr->wr_callback == NULL || gc_is_unreachable((PyObject *)wr)) {
|
|
continue;
|
|
}
|
|
|
|
// Create a new reference so that wr can't go away before we can
|
|
// process it again.
|
|
merge_refcount((PyObject *)wr, 1);
|
|
|
|
// Enqueue weakref to be called later.
|
|
worklist_push(&state->wrcb_to_call, (PyObject *)wr);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void
|
|
call_weakref_callbacks(struct collection_state *state)
|
|
{
|
|
// Invoke the callbacks we decided to honor.
|
|
PyObject *op;
|
|
while ((op = worklist_pop(&state->wrcb_to_call)) != NULL) {
|
|
_PyObject_ASSERT(op, PyWeakref_Check(op));
|
|
|
|
PyWeakReference *wr = (PyWeakReference *)op;
|
|
PyObject *callback = wr->wr_callback;
|
|
_PyObject_ASSERT(op, callback != NULL);
|
|
|
|
/* copy-paste of weakrefobject.c's handle_callback() */
|
|
PyObject *temp = PyObject_CallOneArg(callback, (PyObject *)wr);
|
|
if (temp == NULL) {
|
|
PyErr_WriteUnraisable(callback);
|
|
}
|
|
else {
|
|
Py_DECREF(temp);
|
|
}
|
|
|
|
Py_DECREF(op); // drop worklist reference
|
|
}
|
|
}
|
|
|
|
|
|
static GCState *
|
|
get_gc_state(void)
|
|
{
|
|
PyInterpreterState *interp = _PyInterpreterState_GET();
|
|
return &interp->gc;
|
|
}
|
|
|
|
|
|
void
|
|
_PyGC_InitState(GCState *gcstate)
|
|
{
|
|
// TODO: move to pycore_runtime_init.h once the incremental GC lands.
|
|
gcstate->young.threshold = 2000;
|
|
}
|
|
|
|
|
|
PyStatus
|
|
_PyGC_Init(PyInterpreterState *interp)
|
|
{
|
|
GCState *gcstate = &interp->gc;
|
|
|
|
// gh-117783: immortalize objects that would use deferred refcounting
|
|
// once the first non-main thread is created (but not in subinterpreters).
|
|
gcstate->immortalize = _Py_IsMainInterpreter(interp) ? 0 : -1;
|
|
|
|
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();
|
|
}
|
|
|
|
static void
|
|
debug_cycle(const char *msg, PyObject *op)
|
|
{
|
|
PySys_FormatStderr("gc: %s <%s %p>\n",
|
|
msg, Py_TYPE(op)->tp_name, op);
|
|
}
|
|
|
|
/* 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(struct collection_state *state)
|
|
{
|
|
// NOTE: the unreachable worklist holds a strong reference to the object
|
|
// to prevent it from being deallocated while we are holding on to it.
|
|
PyObject *op;
|
|
WORKSTACK_FOR_EACH(&state->unreachable, op) {
|
|
if (!_PyGC_FINALIZED(op)) {
|
|
destructor finalize = Py_TYPE(op)->tp_finalize;
|
|
if (finalize != NULL) {
|
|
_PyGC_SET_FINALIZED(op);
|
|
finalize(op);
|
|
assert(!_PyErr_Occurred(_PyThreadState_GET()));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Break reference cycles by clearing the containers involved.
|
|
static void
|
|
delete_garbage(struct collection_state *state)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
GCState *gcstate = state->gcstate;
|
|
|
|
assert(!_PyErr_Occurred(tstate));
|
|
|
|
PyObject *op;
|
|
while ((op = worklist_pop(&state->objs_to_decref)) != NULL) {
|
|
Py_DECREF(op);
|
|
}
|
|
|
|
while ((op = worklist_pop(&state->unreachable)) != NULL) {
|
|
_PyObject_ASSERT(op, gc_is_unreachable(op));
|
|
|
|
// Clear the unreachable flag.
|
|
gc_clear_unreachable(op);
|
|
|
|
if (!_PyObject_GC_IS_TRACKED(op)) {
|
|
// Object might have been untracked by some other tp_clear() call.
|
|
Py_DECREF(op); // drop the reference from the worklist
|
|
continue;
|
|
}
|
|
|
|
state->collected++;
|
|
|
|
if (gcstate->debug & _PyGC_DEBUG_SAVEALL) {
|
|
assert(gcstate->garbage != NULL);
|
|
if (PyList_Append(gcstate->garbage, op) < 0) {
|
|
_PyErr_Clear(tstate);
|
|
}
|
|
}
|
|
else {
|
|
inquiry clear = Py_TYPE(op)->tp_clear;
|
|
if (clear != NULL) {
|
|
(void) clear(op);
|
|
if (_PyErr_Occurred(tstate)) {
|
|
PyErr_FormatUnraisable("Exception ignored in tp_clear of %s",
|
|
Py_TYPE(op)->tp_name);
|
|
}
|
|
}
|
|
}
|
|
|
|
Py_DECREF(op); // drop the reference from the worklist
|
|
}
|
|
}
|
|
|
|
static void
|
|
handle_legacy_finalizers(struct collection_state *state)
|
|
{
|
|
GCState *gcstate = state->gcstate;
|
|
assert(gcstate->garbage != NULL);
|
|
|
|
PyObject *op;
|
|
while ((op = worklist_pop(&state->legacy_finalizers)) != NULL) {
|
|
state->uncollectable++;
|
|
|
|
if (gcstate->debug & _PyGC_DEBUG_UNCOLLECTABLE) {
|
|
debug_cycle("uncollectable", op);
|
|
}
|
|
|
|
if ((gcstate->debug & _PyGC_DEBUG_SAVEALL) || has_legacy_finalizer(op)) {
|
|
if (PyList_Append(gcstate->garbage, op) < 0) {
|
|
PyErr_Clear();
|
|
}
|
|
}
|
|
Py_DECREF(op); // drop worklist reference
|
|
}
|
|
}
|
|
|
|
// Show stats for objects in each generations
|
|
static void
|
|
show_stats_each_generations(GCState *gcstate)
|
|
{
|
|
// TODO
|
|
}
|
|
|
|
// Traversal callback for handle_resurrected_objects.
|
|
static int
|
|
visit_decref_unreachable(PyObject *op, void *data)
|
|
{
|
|
if (gc_is_unreachable(op) && _PyObject_GC_IS_TRACKED(op)) {
|
|
op->ob_ref_local -= 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
// Handle objects that may have resurrected after a call to 'finalize_garbage'.
|
|
static int
|
|
handle_resurrected_objects(struct collection_state *state)
|
|
{
|
|
// First, find externally reachable objects by computing the reference
|
|
// count difference in ob_ref_local. We can't use ob_tid here because
|
|
// that's already used to store the unreachable worklist.
|
|
PyObject *op;
|
|
struct worklist_iter iter;
|
|
WORKSTACK_FOR_EACH_ITER(&state->unreachable, &iter, op) {
|
|
assert(gc_is_unreachable(op));
|
|
assert(_Py_REF_IS_MERGED(op->ob_ref_shared));
|
|
|
|
if (!_PyObject_GC_IS_TRACKED(op)) {
|
|
// Object was untracked by a finalizer. Schedule it for a Py_DECREF
|
|
// after we finish with the stop-the-world pause.
|
|
gc_clear_unreachable(op);
|
|
worklist_remove(&iter);
|
|
worklist_push(&state->objs_to_decref, op);
|
|
continue;
|
|
}
|
|
|
|
Py_ssize_t refcount = (op->ob_ref_shared >> _Py_REF_SHARED_SHIFT);
|
|
if (refcount > INT32_MAX) {
|
|
// The refcount is too big to fit in `ob_ref_local`. Mark the
|
|
// object as immortal and bail out.
|
|
gc_clear_unreachable(op);
|
|
worklist_remove(&iter);
|
|
_Py_SetImmortal(op);
|
|
continue;
|
|
}
|
|
|
|
op->ob_ref_local += (uint32_t)refcount;
|
|
|
|
// Subtract one to account for the reference from the worklist.
|
|
op->ob_ref_local -= 1;
|
|
|
|
traverseproc traverse = Py_TYPE(op)->tp_traverse;
|
|
(void) traverse(op,
|
|
(visitproc)visit_decref_unreachable,
|
|
NULL);
|
|
}
|
|
|
|
// Find resurrected objects
|
|
bool any_resurrected = false;
|
|
WORKSTACK_FOR_EACH(&state->unreachable, op) {
|
|
int32_t gc_refs = (int32_t)op->ob_ref_local;
|
|
op->ob_ref_local = 0; // restore ob_ref_local
|
|
|
|
_PyObject_ASSERT(op, gc_refs >= 0);
|
|
|
|
if (gc_is_unreachable(op) && gc_refs > 0) {
|
|
// Clear the unreachable flag on any transitively reachable objects
|
|
// from this one.
|
|
any_resurrected = true;
|
|
gc_clear_unreachable(op);
|
|
if (mark_reachable(op) < 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (any_resurrected) {
|
|
// Remove resurrected objects from the unreachable list.
|
|
WORKSTACK_FOR_EACH_ITER(&state->unreachable, &iter, op) {
|
|
if (!gc_is_unreachable(op)) {
|
|
_PyObject_ASSERT(op, Py_REFCNT(op) > 1);
|
|
worklist_remove(&iter);
|
|
merge_refcount(op, -1); // remove worklist reference
|
|
}
|
|
}
|
|
}
|
|
|
|
#ifdef GC_DEBUG
|
|
WORKSTACK_FOR_EACH(&state->unreachable, op) {
|
|
_PyObject_ASSERT(op, gc_is_unreachable(op));
|
|
_PyObject_ASSERT(op, _PyObject_GC_IS_TRACKED(op));
|
|
_PyObject_ASSERT(op, op->ob_ref_local == 0);
|
|
_PyObject_ASSERT(op, _Py_REF_IS_MERGED(op->ob_ref_shared));
|
|
}
|
|
#endif
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
/* 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_FormatUnraisable("Exception ignored on invoking gc callbacks");
|
|
return;
|
|
}
|
|
}
|
|
|
|
PyObject *phase_obj = PyUnicode_FromString(phase);
|
|
if (phase_obj == NULL) {
|
|
Py_XDECREF(info);
|
|
PyErr_FormatUnraisable("Exception ignored on invoking gc callbacks");
|
|
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));
|
|
}
|
|
|
|
static void
|
|
cleanup_worklist(struct worklist *worklist)
|
|
{
|
|
PyObject *op;
|
|
while ((op = worklist_pop(worklist)) != NULL) {
|
|
gc_clear_unreachable(op);
|
|
Py_DECREF(op);
|
|
}
|
|
}
|
|
|
|
static bool
|
|
gc_should_collect(GCState *gcstate)
|
|
{
|
|
int count = _Py_atomic_load_int_relaxed(&gcstate->young.count);
|
|
int threshold = gcstate->young.threshold;
|
|
if (count <= threshold || threshold == 0 || !gcstate->enabled) {
|
|
return false;
|
|
}
|
|
// Avoid quadratic behavior by scaling threshold to the number of live
|
|
// objects. A few tests rely on immediate scheduling of the GC so we ignore
|
|
// the scaled threshold if generations[1].threshold is set to zero.
|
|
return (count > gcstate->long_lived_total / 4 ||
|
|
gcstate->old[0].threshold == 0);
|
|
}
|
|
|
|
static void
|
|
record_allocation(PyThreadState *tstate)
|
|
{
|
|
struct _gc_thread_state *gc = &((_PyThreadStateImpl *)tstate)->gc;
|
|
|
|
// We buffer the allocation count to avoid the overhead of atomic
|
|
// operations for every allocation.
|
|
gc->alloc_count++;
|
|
if (gc->alloc_count >= LOCAL_ALLOC_COUNT_THRESHOLD) {
|
|
// TODO: Use Py_ssize_t for the generation count.
|
|
GCState *gcstate = &tstate->interp->gc;
|
|
_Py_atomic_add_int(&gcstate->young.count, (int)gc->alloc_count);
|
|
gc->alloc_count = 0;
|
|
|
|
if (gc_should_collect(gcstate) &&
|
|
!_Py_atomic_load_int_relaxed(&gcstate->collecting))
|
|
{
|
|
_Py_ScheduleGC(tstate);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void
|
|
record_deallocation(PyThreadState *tstate)
|
|
{
|
|
struct _gc_thread_state *gc = &((_PyThreadStateImpl *)tstate)->gc;
|
|
|
|
gc->alloc_count--;
|
|
if (gc->alloc_count <= -LOCAL_ALLOC_COUNT_THRESHOLD) {
|
|
GCState *gcstate = &tstate->interp->gc;
|
|
_Py_atomic_add_int(&gcstate->young.count, (int)gc->alloc_count);
|
|
gc->alloc_count = 0;
|
|
}
|
|
}
|
|
|
|
static void
|
|
gc_collect_internal(PyInterpreterState *interp, struct collection_state *state, int generation)
|
|
{
|
|
_PyEval_StopTheWorld(interp);
|
|
|
|
// update collection and allocation counters
|
|
if (generation+1 < NUM_GENERATIONS) {
|
|
state->gcstate->old[generation].count += 1;
|
|
}
|
|
|
|
state->gcstate->young.count = 0;
|
|
for (int i = 1; i <= generation; ++i) {
|
|
state->gcstate->old[i-1].count = 0;
|
|
}
|
|
|
|
// merge refcounts for all queued objects
|
|
merge_all_queued_objects(interp, state);
|
|
process_delayed_frees(interp);
|
|
|
|
// Find unreachable objects
|
|
int err = deduce_unreachable_heap(interp, state);
|
|
if (err < 0) {
|
|
_PyEval_StartTheWorld(interp);
|
|
goto error;
|
|
}
|
|
|
|
// Print debugging information.
|
|
if (interp->gc.debug & _PyGC_DEBUG_COLLECTABLE) {
|
|
PyObject *op;
|
|
WORKSTACK_FOR_EACH(&state->unreachable, op) {
|
|
debug_cycle("collectable", op);
|
|
}
|
|
}
|
|
|
|
// Record the number of live GC objects
|
|
interp->gc.long_lived_total = state->long_lived_total;
|
|
|
|
// Clear weakrefs and enqueue callbacks (but do not call them).
|
|
clear_weakrefs(state);
|
|
_PyEval_StartTheWorld(interp);
|
|
|
|
// Deallocate any object from the refcount merge step
|
|
cleanup_worklist(&state->objs_to_decref);
|
|
|
|
// Call weakref callbacks and finalizers after unpausing other threads to
|
|
// avoid potential deadlocks.
|
|
call_weakref_callbacks(state);
|
|
finalize_garbage(state);
|
|
|
|
// Handle any objects that may have resurrected after the finalization.
|
|
_PyEval_StopTheWorld(interp);
|
|
err = handle_resurrected_objects(state);
|
|
// Clear free lists in all threads
|
|
_PyGC_ClearAllFreeLists(interp);
|
|
_PyEval_StartTheWorld(interp);
|
|
|
|
if (err < 0) {
|
|
goto error;
|
|
}
|
|
|
|
// Call tp_clear on objects in the unreachable set. This will cause
|
|
// the reference cycles to be broken. It may also cause some objects
|
|
// to be freed.
|
|
delete_garbage(state);
|
|
|
|
// Append objects with legacy finalizers to the "gc.garbage" list.
|
|
handle_legacy_finalizers(state);
|
|
return;
|
|
|
|
error:
|
|
cleanup_worklist(&state->unreachable);
|
|
cleanup_worklist(&state->legacy_finalizers);
|
|
cleanup_worklist(&state->wrcb_to_call);
|
|
cleanup_worklist(&state->objs_to_decref);
|
|
PyErr_NoMemory();
|
|
PyErr_FormatUnraisable("Out of memory during garbage collection");
|
|
}
|
|
|
|
/* 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, _PyGC_Reason reason)
|
|
{
|
|
Py_ssize_t m = 0; /* # objects collected */
|
|
Py_ssize_t n = 0; /* # unreachable objects that couldn't be collected */
|
|
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));
|
|
|
|
int expected = 0;
|
|
if (!_Py_atomic_compare_exchange_int(&gcstate->collecting, &expected, 1)) {
|
|
// Don't start a garbage collection if one is already in progress.
|
|
return 0;
|
|
}
|
|
|
|
if (reason == _Py_GC_REASON_HEAP && !gc_should_collect(gcstate)) {
|
|
// Don't collect if the threshold is not exceeded.
|
|
_Py_atomic_store_int(&gcstate->collecting, 0);
|
|
return 0;
|
|
}
|
|
|
|
assert(generation >= 0 && generation < NUM_GENERATIONS);
|
|
|
|
#ifdef Py_STATS
|
|
if (_Py_stats) {
|
|
_Py_stats->object_stats.object_visits = 0;
|
|
}
|
|
#endif
|
|
GC_STAT_ADD(generation, collections, 1);
|
|
|
|
if (reason != _Py_GC_REASON_SHUTDOWN) {
|
|
invoke_gc_callback(tstate, "start", generation, 0, 0);
|
|
}
|
|
|
|
if (gcstate->debug & _PyGC_DEBUG_STATS) {
|
|
PySys_WriteStderr("gc: collecting generation %d...\n", generation);
|
|
show_stats_each_generations(gcstate);
|
|
// ignore error: don't interrupt the GC if reading the clock fails
|
|
(void)PyTime_PerfCounterRaw(&t1);
|
|
}
|
|
|
|
if (PyDTrace_GC_START_ENABLED()) {
|
|
PyDTrace_GC_START(generation);
|
|
}
|
|
|
|
PyInterpreterState *interp = tstate->interp;
|
|
|
|
struct collection_state state = {
|
|
.interp = interp,
|
|
.gcstate = gcstate,
|
|
};
|
|
|
|
gc_collect_internal(interp, &state, generation);
|
|
|
|
m = state.collected;
|
|
n = state.uncollectable;
|
|
|
|
if (gcstate->debug & _PyGC_DEBUG_STATS) {
|
|
PyTime_t t2;
|
|
(void)PyTime_PerfCounterRaw(&t2);
|
|
double d = PyTime_AsSecondsDouble(t2 - t1);
|
|
PySys_WriteStderr(
|
|
"gc: done, %zd unreachable, %zd uncollectable, %.4fs elapsed\n",
|
|
n+m, n, d);
|
|
}
|
|
|
|
// Clear the current thread's free-list again.
|
|
_PyThreadStateImpl *tstate_impl = (_PyThreadStateImpl *)tstate;
|
|
_PyObject_ClearFreeLists(&tstate_impl->freelists, 0);
|
|
|
|
if (_PyErr_Occurred(tstate)) {
|
|
if (reason == _Py_GC_REASON_SHUTDOWN) {
|
|
_PyErr_Clear(tstate);
|
|
}
|
|
else {
|
|
PyErr_FormatUnraisable("Exception ignored in garbage collection");
|
|
}
|
|
}
|
|
|
|
/* Update stats */
|
|
struct gc_generation_stats *stats = &gcstate->generation_stats[generation];
|
|
stats->collections++;
|
|
stats->collected += m;
|
|
stats->uncollectable += n;
|
|
|
|
GC_STAT_ADD(generation, objects_collected, m);
|
|
#ifdef Py_STATS
|
|
if (_Py_stats) {
|
|
GC_STAT_ADD(generation, object_visits,
|
|
_Py_stats->object_stats.object_visits);
|
|
_Py_stats->object_stats.object_visits = 0;
|
|
}
|
|
#endif
|
|
|
|
if (PyDTrace_GC_DONE_ENABLED()) {
|
|
PyDTrace_GC_DONE(n + m);
|
|
}
|
|
|
|
if (reason != _Py_GC_REASON_SHUTDOWN) {
|
|
invoke_gc_callback(tstate, "stop", generation, m, n);
|
|
}
|
|
|
|
assert(!_PyErr_Occurred(tstate));
|
|
_Py_atomic_store_int(&gcstate->collecting, 0);
|
|
return n + m;
|
|
}
|
|
|
|
struct get_referrers_args {
|
|
struct visitor_args base;
|
|
PyObject *objs;
|
|
struct worklist results;
|
|
};
|
|
|
|
static int
|
|
referrersvisit(PyObject* obj, void *arg)
|
|
{
|
|
PyObject *objs = arg;
|
|
Py_ssize_t i;
|
|
for (i = 0; i < PyTuple_GET_SIZE(objs); i++) {
|
|
if (PyTuple_GET_ITEM(objs, i) == obj) {
|
|
return 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static bool
|
|
visit_get_referrers(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, true);
|
|
if (op == NULL) {
|
|
return true;
|
|
}
|
|
|
|
struct get_referrers_args *arg = (struct get_referrers_args *)args;
|
|
if (Py_TYPE(op)->tp_traverse(op, referrersvisit, arg->objs)) {
|
|
op->ob_tid = 0; // we will restore the refcount later
|
|
worklist_push(&arg->results, op);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
PyObject *
|
|
_PyGC_GetReferrers(PyInterpreterState *interp, PyObject *objs)
|
|
{
|
|
PyObject *result = PyList_New(0);
|
|
if (!result) {
|
|
return NULL;
|
|
}
|
|
|
|
_PyEval_StopTheWorld(interp);
|
|
|
|
// Append all objects to a worklist. This abuses ob_tid. We will restore
|
|
// it later. NOTE: We can't append to the PyListObject during
|
|
// gc_visit_heaps() because PyList_Append() may reclaim an abandoned
|
|
// mimalloc segments while we are traversing them.
|
|
struct get_referrers_args args = { .objs = objs };
|
|
gc_visit_heaps(interp, &visit_get_referrers, &args.base);
|
|
|
|
bool error = false;
|
|
PyObject *op;
|
|
while ((op = worklist_pop(&args.results)) != NULL) {
|
|
gc_restore_tid(op);
|
|
if (op != objs && PyList_Append(result, op) < 0) {
|
|
error = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// In case of error, clear the remaining worklist
|
|
while ((op = worklist_pop(&args.results)) != NULL) {
|
|
gc_restore_tid(op);
|
|
}
|
|
|
|
_PyEval_StartTheWorld(interp);
|
|
|
|
if (error) {
|
|
Py_DECREF(result);
|
|
return NULL;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
struct get_objects_args {
|
|
struct visitor_args base;
|
|
struct worklist objects;
|
|
};
|
|
|
|
static bool
|
|
visit_get_objects(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, true);
|
|
if (op == NULL) {
|
|
return true;
|
|
}
|
|
|
|
struct get_objects_args *arg = (struct get_objects_args *)args;
|
|
op->ob_tid = 0; // we will restore the refcount later
|
|
worklist_push(&arg->objects, op);
|
|
|
|
return true;
|
|
}
|
|
|
|
PyObject *
|
|
_PyGC_GetObjects(PyInterpreterState *interp, int generation)
|
|
{
|
|
PyObject *result = PyList_New(0);
|
|
if (!result) {
|
|
return NULL;
|
|
}
|
|
|
|
_PyEval_StopTheWorld(interp);
|
|
|
|
// Append all objects to a worklist. This abuses ob_tid. We will restore
|
|
// it later. NOTE: We can't append to the list during gc_visit_heaps()
|
|
// because PyList_Append() may reclaim an abandoned mimalloc segment
|
|
// while we are traversing it.
|
|
struct get_objects_args args = { 0 };
|
|
gc_visit_heaps(interp, &visit_get_objects, &args.base);
|
|
|
|
bool error = false;
|
|
PyObject *op;
|
|
while ((op = worklist_pop(&args.objects)) != NULL) {
|
|
gc_restore_tid(op);
|
|
if (op != result && PyList_Append(result, op) < 0) {
|
|
error = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// In case of error, clear the remaining worklist
|
|
while ((op = worklist_pop(&args.objects)) != NULL) {
|
|
gc_restore_tid(op);
|
|
}
|
|
|
|
_PyEval_StartTheWorld(interp);
|
|
|
|
if (error) {
|
|
Py_DECREF(result);
|
|
return NULL;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
static bool
|
|
visit_freeze(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, true);
|
|
if (op != NULL) {
|
|
op->ob_gc_bits |= _PyGC_BITS_FROZEN;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void
|
|
_PyGC_Freeze(PyInterpreterState *interp)
|
|
{
|
|
struct visitor_args args;
|
|
_PyEval_StopTheWorld(interp);
|
|
gc_visit_heaps(interp, &visit_freeze, &args);
|
|
_PyEval_StartTheWorld(interp);
|
|
}
|
|
|
|
static bool
|
|
visit_unfreeze(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, true);
|
|
if (op != NULL) {
|
|
op->ob_gc_bits &= ~_PyGC_BITS_FROZEN;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void
|
|
_PyGC_Unfreeze(PyInterpreterState *interp)
|
|
{
|
|
struct visitor_args args;
|
|
_PyEval_StopTheWorld(interp);
|
|
gc_visit_heaps(interp, &visit_unfreeze, &args);
|
|
_PyEval_StartTheWorld(interp);
|
|
}
|
|
|
|
struct count_frozen_args {
|
|
struct visitor_args base;
|
|
Py_ssize_t count;
|
|
};
|
|
|
|
static bool
|
|
visit_count_frozen(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, true);
|
|
if (op != NULL && (op->ob_gc_bits & _PyGC_BITS_FROZEN) != 0) {
|
|
struct count_frozen_args *arg = (struct count_frozen_args *)args;
|
|
arg->count++;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
Py_ssize_t
|
|
_PyGC_GetFreezeCount(PyInterpreterState *interp)
|
|
{
|
|
struct count_frozen_args args = { .count = 0 };
|
|
_PyEval_StopTheWorld(interp);
|
|
gc_visit_heaps(interp, &visit_count_frozen, &args.base);
|
|
_PyEval_StartTheWorld(interp);
|
|
return args.count;
|
|
}
|
|
|
|
/* 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;
|
|
PyObject *exc = _PyErr_GetRaisedException(tstate);
|
|
n = gc_collect_main(tstate, NUM_GENERATIONS - 1, _Py_GC_REASON_MANUAL);
|
|
_PyErr_SetRaisedException(tstate, exc);
|
|
|
|
return n;
|
|
}
|
|
|
|
Py_ssize_t
|
|
_PyGC_Collect(PyThreadState *tstate, int generation, _PyGC_Reason reason)
|
|
{
|
|
return gc_collect_main(tstate, generation, reason);
|
|
}
|
|
|
|
void
|
|
_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.
|
|
*/
|
|
gc_collect_main(tstate, NUM_GENERATIONS - 1, _Py_GC_REASON_SHUTDOWN);
|
|
}
|
|
|
|
void
|
|
_PyGC_DumpShutdownStats(PyInterpreterState *interp)
|
|
{
|
|
GCState *gcstate = &interp->gc;
|
|
if (!(gcstate->debug & _PyGC_DEBUG_SAVEALL)
|
|
&& gcstate->garbage != NULL && PyList_GET_SIZE(gcstate->garbage) > 0) {
|
|
const char *message;
|
|
if (gcstate->debug & _PyGC_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 & _PyGC_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);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
void
|
|
_PyGC_Fini(PyInterpreterState *interp)
|
|
{
|
|
GCState *gcstate = &interp->gc;
|
|
Py_CLEAR(gcstate->garbage);
|
|
Py_CLEAR(gcstate->callbacks);
|
|
|
|
/* We expect that none of this interpreters objects are shared
|
|
with other interpreters.
|
|
See https://github.com/python/cpython/issues/90228. */
|
|
}
|
|
|
|
/* for debugging */
|
|
|
|
#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(PyThreadState *tstate)
|
|
{
|
|
if (!_Py_eval_breaker_bit_is_set(tstate, _PY_GC_SCHEDULED_BIT))
|
|
{
|
|
_Py_set_eval_breaker_bit(tstate, _PY_GC_SCHEDULED_BIT);
|
|
}
|
|
}
|
|
|
|
void
|
|
_PyObject_GC_Link(PyObject *op)
|
|
{
|
|
record_allocation(_PyThreadState_GET());
|
|
}
|
|
|
|
void
|
|
_Py_RunGC(PyThreadState *tstate)
|
|
{
|
|
GCState *gcstate = get_gc_state();
|
|
if (!gcstate->enabled) {
|
|
return;
|
|
}
|
|
gc_collect_main(tstate, 0, _Py_GC_REASON_HEAP);
|
|
}
|
|
|
|
static PyObject *
|
|
gc_alloc(PyTypeObject *tp, 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_MallocWithType(tp, size);
|
|
if (mem == NULL) {
|
|
return _PyErr_NoMemory(tstate);
|
|
}
|
|
if (presize) {
|
|
((PyObject **)mem)[0] = NULL;
|
|
((PyObject **)mem)[1] = NULL;
|
|
}
|
|
PyObject *op = (PyObject *)(mem + presize);
|
|
record_allocation(tstate);
|
|
return op;
|
|
}
|
|
|
|
PyObject *
|
|
_PyObject_GC_New(PyTypeObject *tp)
|
|
{
|
|
size_t presize = _PyType_PreHeaderSize(tp);
|
|
size_t size = _PyObject_SIZE(tp);
|
|
if (_PyType_HasFeature(tp, Py_TPFLAGS_INLINE_VALUES)) {
|
|
size += _PyInlineValuesSize(tp);
|
|
}
|
|
PyObject *op = gc_alloc(tp, size, 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(tp, 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(tp, _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_ReallocWithType(Py_TYPE(op), 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);
|
|
if (_PyObject_GC_IS_TRACKED(op)) {
|
|
_PyObject_GC_UNTRACK(op);
|
|
#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
|
|
}
|
|
|
|
record_deallocation(_PyThreadState_GET());
|
|
PyObject *self = (PyObject *)op;
|
|
if (_PyObject_GC_IS_SHARED_INLINE(self)) {
|
|
_PyObject_FreeDelayed(((char *)op)-presize);
|
|
}
|
|
else {
|
|
PyObject_Free(((char *)op)-presize);
|
|
}
|
|
}
|
|
|
|
int
|
|
PyObject_GC_IsTracked(PyObject* obj)
|
|
{
|
|
return _PyObject_GC_IS_TRACKED(obj);
|
|
}
|
|
|
|
int
|
|
PyObject_GC_IsFinalized(PyObject *obj)
|
|
{
|
|
return _PyGC_FINALIZED(obj);
|
|
}
|
|
|
|
struct custom_visitor_args {
|
|
struct visitor_args base;
|
|
gcvisitobjects_t callback;
|
|
void *arg;
|
|
};
|
|
|
|
static bool
|
|
custom_visitor_wrapper(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, false);
|
|
if (op == NULL) {
|
|
return true;
|
|
}
|
|
|
|
struct custom_visitor_args *wrapper = (struct custom_visitor_args *)args;
|
|
if (!wrapper->callback(op, wrapper->arg)) {
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
// gh-117783: Immortalize objects that use deferred reference counting to
|
|
// temporarily work around scaling bottlenecks.
|
|
static bool
|
|
immortalize_visitor(const mi_heap_t *heap, const mi_heap_area_t *area,
|
|
void *block, size_t block_size, void *args)
|
|
{
|
|
PyObject *op = op_from_block(block, args, false);
|
|
if (op != NULL && _PyObject_HasDeferredRefcount(op)) {
|
|
_Py_SetImmortal(op);
|
|
op->ob_gc_bits &= ~_PyGC_BITS_DEFERRED;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void
|
|
_PyGC_ImmortalizeDeferredObjects(PyInterpreterState *interp)
|
|
{
|
|
struct visitor_args args;
|
|
_PyEval_StopTheWorld(interp);
|
|
if (interp->gc.immortalize == 0) {
|
|
gc_visit_heaps(interp, &immortalize_visitor, &args);
|
|
interp->gc.immortalize = 1;
|
|
}
|
|
_PyEval_StartTheWorld(interp);
|
|
}
|
|
|
|
void
|
|
PyUnstable_GC_VisitObjects(gcvisitobjects_t callback, void *arg)
|
|
{
|
|
PyInterpreterState *interp = _PyInterpreterState_GET();
|
|
struct custom_visitor_args wrapper = {
|
|
.callback = callback,
|
|
.arg = arg,
|
|
};
|
|
|
|
_PyEval_StopTheWorld(interp);
|
|
gc_visit_heaps(interp, &custom_visitor_wrapper, &wrapper.base);
|
|
_PyEval_StartTheWorld(interp);
|
|
}
|
|
|
|
/* 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.
|
|
* Free-threading version: Since freelists are managed per thread,
|
|
* GC should clear all freelists by traversing all threads.
|
|
*/
|
|
void
|
|
_PyGC_ClearAllFreeLists(PyInterpreterState *interp)
|
|
{
|
|
HEAD_LOCK(&_PyRuntime);
|
|
_PyThreadStateImpl *tstate = (_PyThreadStateImpl *)interp->threads.head;
|
|
while (tstate != NULL) {
|
|
_PyObject_ClearFreeLists(&tstate->freelists, 0);
|
|
tstate = (_PyThreadStateImpl *)tstate->base.next;
|
|
}
|
|
HEAD_UNLOCK(&_PyRuntime);
|
|
}
|
|
|
|
#endif // Py_GIL_DISABLED
|