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php-src/Zend/zend_gc.c
Arnaud Le Blanc c13794cdcb
Adjust GC threshold if num_roots is higher than gc_threshold after collection (#13758) 
This fixes an edge case causing the GC to be triggered repeatedly.

Destructors might add potential garbage to the buffer, so it may happen that num_root it higher than gc_threshold after collection, thus triggering a GC run almost immediately. This can happen by touching enough objects in a destructor, e.g. by iterating over an array. If this happens again in the new run, and the threshold is not updated, the GC may be triggered again.

The edge case requires specific conditions to be triggered and it must happen rarely in practice:

 * At least GC_THRESHOLD_TRIGGER (100) objects must be collected during each run for the threshold to not be updated
 * At least GC_G(gc_threshold) (initially 10k) objects must be touched (decref'ed to n>0) by any destructor during each run to fill the buffer

The fix is to increase the threshold if GC_G(num_roots) >= GC_G(gc_threshold) after GC. The threshold eventually reaches a point at which the second condition is not met anymore.

The included tests trigger more than 200 GC runs before the fix, and 2 after the fix (dtors always trigger a second run).

A related issue is that zend_gc_check_root_tmpvars() may add potential garbage before the threshold is adjusted, which may trigger GC and exhaust the stack. This is fixed by setting GC_G(active)=1 around zend_gc_check_root_tmpvars().
2024-03-25 16:17:54 +01:00

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/*
+----------------------------------------------------------------------+
| Zend Engine |
+----------------------------------------------------------------------+
| Copyright (c) Zend Technologies Ltd. (http://www.zend.com) |
+----------------------------------------------------------------------+
| This source file is subject to version 2.00 of the Zend license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.zend.com/license/2_00.txt. |
| If you did not receive a copy of the Zend license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@zend.com so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: David Wang <planetbeing@gmail.com> |
| Dmitry Stogov <dmitry@php.net> |
+----------------------------------------------------------------------+
*/
/**
* zend_gc_collect_cycles
* ======================
*
* Colors and its meaning
* ----------------------
*
* BLACK (GC_BLACK) - In use or free.
* GREY (GC_GREY) - Possible member of cycle.
* WHITE (GC_WHITE) - Member of garbage cycle.
* PURPLE (GC_PURPLE) - Possible root of cycle.
*
* Colors described in the paper but not used
* ------------------------------------------
*
* GREEN - Acyclic
* RED - Candidate cycle undergoing
* ORANGE - Candidate cycle awaiting epoch boundary.
*
*
* Flow
* =====
*
* The garbage collect cycle starts from 'gc_mark_roots', which traverses the
* possible roots, and calls mark_grey for roots are marked purple with
* depth-first traverse.
*
* After all possible roots are traversed and marked,
* gc_scan_roots will be called, and each root will be called with
* gc_scan(root->ref)
*
* gc_scan checks the colors of possible members.
*
* If the node is marked as grey and the refcount > 0
* gc_scan_black will be called on that node to scan it's subgraph.
* otherwise (refcount == 0), it marks the node white.
*
* A node MAY be added to possible roots when ZEND_UNSET_VAR happens or
* zend_assign_to_variable is called only when possible garbage node is
* produced.
* gc_possible_root() will be called to add the nodes to possible roots.
*
*
* For objects, we call their get_gc handler (by default 'zend_std_get_gc') to
* get the object properties to scan.
*
*
* @see http://researcher.watson.ibm.com/researcher/files/us-bacon/Bacon01Concurrent.pdf
*/
#include "zend.h"
#include "zend_API.h"
#include "zend_fibers.h"
#ifndef GC_BENCH
# define GC_BENCH 0
#endif
#ifndef ZEND_GC_DEBUG
# define ZEND_GC_DEBUG 0
#endif
/* GC_INFO layout */
#define GC_ADDRESS 0x0fffffu
#define GC_COLOR 0x300000u
#define GC_BLACK 0x000000u /* must be zero */
#define GC_WHITE 0x100000u
#define GC_GREY 0x200000u
#define GC_PURPLE 0x300000u
/* Debug tracing */
#if ZEND_GC_DEBUG > 1
# define GC_TRACE(format, ...) fprintf(stderr, format "\n", ##__VA_ARGS__);
# define GC_TRACE_REF(ref, format, ...) \
do { \
gc_trace_ref((zend_refcounted *) ref); \
fprintf(stderr, format "\n", ##__VA_ARGS__); \
} while (0)
# define GC_TRACE_SET_COLOR(ref, color) \
GC_TRACE_REF(ref, "->%s", gc_color_name(color))
#else
# define GC_TRACE_REF(ref, format, ...)
# define GC_TRACE_SET_COLOR(ref, new_color)
# define GC_TRACE(str)
#endif
/* GC_INFO access */
#define GC_REF_ADDRESS(ref) \
(((GC_TYPE_INFO(ref)) & (GC_ADDRESS << GC_INFO_SHIFT)) >> GC_INFO_SHIFT)
#define GC_REF_COLOR(ref) \
(((GC_TYPE_INFO(ref)) & (GC_COLOR << GC_INFO_SHIFT)) >> GC_INFO_SHIFT)
#define GC_REF_CHECK_COLOR(ref, color) \
((GC_TYPE_INFO(ref) & (GC_COLOR << GC_INFO_SHIFT)) == ((color) << GC_INFO_SHIFT))
#define GC_REF_SET_INFO(ref, info) do { \
GC_TYPE_INFO(ref) = \
(GC_TYPE_INFO(ref) & (GC_TYPE_MASK | GC_FLAGS_MASK)) | \
((info) << GC_INFO_SHIFT); \
} while (0)
#define GC_REF_SET_COLOR(ref, c) do { \
GC_TRACE_SET_COLOR(ref, c); \
GC_TYPE_INFO(ref) = \
(GC_TYPE_INFO(ref) & ~(GC_COLOR << GC_INFO_SHIFT)) | \
((c) << GC_INFO_SHIFT); \
} while (0)
#define GC_REF_SET_BLACK(ref) do { \
GC_TRACE_SET_COLOR(ref, GC_BLACK); \
GC_TYPE_INFO(ref) &= ~(GC_COLOR << GC_INFO_SHIFT); \
} while (0)
#define GC_REF_SET_PURPLE(ref) do { \
GC_TRACE_SET_COLOR(ref, GC_PURPLE); \
GC_TYPE_INFO(ref) |= (GC_COLOR << GC_INFO_SHIFT); \
} while (0)
/* bit stealing tags for gc_root_buffer.ref */
#define GC_BITS 0x3
#define GC_ROOT 0x0 /* possible root of circular garbage */
#define GC_UNUSED 0x1 /* part of linked list of unused buffers */
#define GC_GARBAGE 0x2 /* garbage to delete */
#define GC_DTOR_GARBAGE 0x3 /* garbage on which only the dtor should be invoked */
#define GC_GET_PTR(ptr) \
((void*)(((uintptr_t)(ptr)) & ~GC_BITS))
#define GC_IS_ROOT(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_ROOT)
#define GC_IS_UNUSED(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_UNUSED)
#define GC_IS_GARBAGE(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_GARBAGE)
#define GC_IS_DTOR_GARBAGE(ptr) \
((((uintptr_t)(ptr)) & GC_BITS) == GC_DTOR_GARBAGE)
#define GC_MAKE_GARBAGE(ptr) \
((void*)(((uintptr_t)(ptr)) | GC_GARBAGE))
#define GC_MAKE_DTOR_GARBAGE(ptr) \
((void*)(((uintptr_t)(ptr)) | GC_DTOR_GARBAGE))
/* GC address conversion */
#define GC_IDX2PTR(idx) (GC_G(buf) + (idx))
#define GC_PTR2IDX(ptr) ((ptr) - GC_G(buf))
#define GC_IDX2LIST(idx) ((void*)(uintptr_t)(((idx) * sizeof(void*)) | GC_UNUSED))
#define GC_LIST2IDX(list) (((uint32_t)(uintptr_t)(list)) / sizeof(void*))
/* GC buffers */
#define GC_INVALID 0
#define GC_FIRST_ROOT 1
#define GC_DEFAULT_BUF_SIZE (16 * 1024)
#define GC_BUF_GROW_STEP (128 * 1024)
#define GC_MAX_UNCOMPRESSED (512 * 1024)
#define GC_MAX_BUF_SIZE 0x40000000
#define GC_THRESHOLD_DEFAULT (10000 + GC_FIRST_ROOT)
#define GC_THRESHOLD_STEP 10000
#define GC_THRESHOLD_MAX 1000000000
#define GC_THRESHOLD_TRIGGER 100
/* GC flags */
#define GC_HAS_DESTRUCTORS (1<<0)
/* unused buffers */
#define GC_HAS_UNUSED() \
(GC_G(unused) != GC_INVALID)
#define GC_FETCH_UNUSED() \
gc_fetch_unused()
#define GC_LINK_UNUSED(root) \
gc_link_unused(root)
#define GC_HAS_NEXT_UNUSED_UNDER_THRESHOLD() \
(GC_G(first_unused) < GC_G(gc_threshold))
#define GC_HAS_NEXT_UNUSED() \
(GC_G(first_unused) != GC_G(buf_size))
#define GC_FETCH_NEXT_UNUSED() \
gc_fetch_next_unused()
ZEND_API int (*gc_collect_cycles)(void);
typedef struct _gc_root_buffer {
zend_refcounted *ref;
} gc_root_buffer;
typedef struct _zend_gc_globals {
gc_root_buffer *buf; /* preallocated arrays of buffers */
bool gc_enabled;
bool gc_active; /* GC currently running, forbid nested GC */
bool gc_protected; /* GC protected, forbid root additions */
bool gc_full;
uint32_t unused; /* linked list of unused buffers */
uint32_t first_unused; /* first unused buffer */
uint32_t gc_threshold; /* GC collection threshold */
uint32_t buf_size; /* size of the GC buffer */
uint32_t num_roots; /* number of roots in GC buffer */
uint32_t gc_runs;
uint32_t collected;
#if GC_BENCH
uint32_t root_buf_length;
uint32_t root_buf_peak;
uint32_t zval_possible_root;
uint32_t zval_buffered;
uint32_t zval_remove_from_buffer;
uint32_t zval_marked_grey;
#endif
} zend_gc_globals;
#ifdef ZTS
static int gc_globals_id;
static size_t gc_globals_offset;
#define GC_G(v) ZEND_TSRMG_FAST(gc_globals_offset, zend_gc_globals *, v)
#else
#define GC_G(v) (gc_globals.v)
static zend_gc_globals gc_globals;
#endif
#if GC_BENCH
# define GC_BENCH_INC(counter) GC_G(counter)++
# define GC_BENCH_DEC(counter) GC_G(counter)--
# define GC_BENCH_PEAK(peak, counter) do { \
if (GC_G(counter) > GC_G(peak)) { \
GC_G(peak) = GC_G(counter); \
} \
} while (0)
#else
# define GC_BENCH_INC(counter)
# define GC_BENCH_DEC(counter)
# define GC_BENCH_PEAK(peak, counter)
#endif
#define GC_STACK_SEGMENT_SIZE (((4096 - ZEND_MM_OVERHEAD) / sizeof(void*)) - 2)
typedef struct _gc_stack gc_stack;
struct _gc_stack {
gc_stack *prev;
gc_stack *next;
zend_refcounted *data[GC_STACK_SEGMENT_SIZE];
};
#define GC_STACK_DCL(init) \
gc_stack *_stack = init; \
size_t _top = 0;
#define GC_STACK_PUSH(ref) \
gc_stack_push(&_stack, &_top, ref);
#define GC_STACK_POP() \
gc_stack_pop(&_stack, &_top)
static zend_never_inline gc_stack* gc_stack_next(gc_stack *stack)
{
if (UNEXPECTED(!stack->next)) {
gc_stack *segment = emalloc(sizeof(gc_stack));
segment->prev = stack;
segment->next = NULL;
stack->next = segment;
}
return stack->next;
}
static zend_always_inline void gc_stack_push(gc_stack **stack, size_t *top, zend_refcounted *ref)
{
if (UNEXPECTED(*top == GC_STACK_SEGMENT_SIZE)) {
(*stack) = gc_stack_next(*stack);
(*top) = 0;
}
(*stack)->data[(*top)++] = ref;
}
static zend_always_inline zend_refcounted* gc_stack_pop(gc_stack **stack, size_t *top)
{
if (UNEXPECTED((*top) == 0)) {
if (!(*stack)->prev) {
return NULL;
} else {
(*stack) = (*stack)->prev;
(*top) = GC_STACK_SEGMENT_SIZE - 1;
return (*stack)->data[GC_STACK_SEGMENT_SIZE - 1];
}
} else {
return (*stack)->data[--(*top)];
}
}
static void gc_stack_free(gc_stack *stack)
{
gc_stack *p = stack->next;
while (p) {
stack = p->next;
efree(p);
p = stack;
}
}
static zend_always_inline uint32_t gc_compress(uint32_t idx)
{
if (EXPECTED(idx < GC_MAX_UNCOMPRESSED)) {
return idx;
}
return (idx % GC_MAX_UNCOMPRESSED) | GC_MAX_UNCOMPRESSED;
}
static zend_always_inline gc_root_buffer* gc_decompress(zend_refcounted *ref, uint32_t idx)
{
gc_root_buffer *root = GC_IDX2PTR(idx);
if (EXPECTED(GC_GET_PTR(root->ref) == ref)) {
return root;
}
while (1) {
idx += GC_MAX_UNCOMPRESSED;
ZEND_ASSERT(idx < GC_G(first_unused));
root = GC_IDX2PTR(idx);
if (GC_GET_PTR(root->ref) == ref) {
return root;
}
}
}
static zend_always_inline uint32_t gc_fetch_unused(void)
{
uint32_t idx;
gc_root_buffer *root;
ZEND_ASSERT(GC_HAS_UNUSED());
idx = GC_G(unused);
root = GC_IDX2PTR(idx);
ZEND_ASSERT(GC_IS_UNUSED(root->ref));
GC_G(unused) = GC_LIST2IDX(root->ref);
return idx;
}
static zend_always_inline void gc_link_unused(gc_root_buffer *root)
{
root->ref = GC_IDX2LIST(GC_G(unused));
GC_G(unused) = GC_PTR2IDX(root);
}
static zend_always_inline uint32_t gc_fetch_next_unused(void)
{
uint32_t idx;
ZEND_ASSERT(GC_HAS_NEXT_UNUSED());
idx = GC_G(first_unused);
GC_G(first_unused) = GC_G(first_unused) + 1;
return idx;
}
#if ZEND_GC_DEBUG > 1
static const char *gc_color_name(uint32_t color) {
switch (color) {
case GC_BLACK: return "black";
case GC_WHITE: return "white";
case GC_GREY: return "grey";
case GC_PURPLE: return "purple";
default: return "unknown";
}
}
static void gc_trace_ref(zend_refcounted *ref) {
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object *) ref;
fprintf(stderr, "[%p] rc=%d addr=%d %s object(%s)#%d ",
ref, GC_REFCOUNT(ref), GC_REF_ADDRESS(ref),
gc_color_name(GC_REF_COLOR(ref)),
obj->ce->name->val, obj->handle);
} else if (GC_TYPE(ref) == IS_ARRAY) {
zend_array *arr = (zend_array *) ref;
fprintf(stderr, "[%p] rc=%d addr=%d %s array(%d) ",
ref, GC_REFCOUNT(ref), GC_REF_ADDRESS(ref),
gc_color_name(GC_REF_COLOR(ref)),
zend_hash_num_elements(arr));
} else {
fprintf(stderr, "[%p] rc=%d addr=%d %s %s ",
ref, GC_REFCOUNT(ref), GC_REF_ADDRESS(ref),
gc_color_name(GC_REF_COLOR(ref)),
GC_TYPE(ref) == IS_REFERENCE
? "reference" : zend_get_type_by_const(GC_TYPE(ref)));
}
}
#endif
static zend_always_inline void gc_remove_from_roots(gc_root_buffer *root)
{
GC_LINK_UNUSED(root);
GC_G(num_roots)--;
GC_BENCH_DEC(root_buf_length);
}
static void root_buffer_dtor(zend_gc_globals *gc_globals)
{
if (gc_globals->buf) {
free(gc_globals->buf);
gc_globals->buf = NULL;
}
}
static void gc_globals_ctor_ex(zend_gc_globals *gc_globals)
{
gc_globals->gc_enabled = 0;
gc_globals->gc_active = 0;
gc_globals->gc_protected = 1;
gc_globals->gc_full = 0;
gc_globals->buf = NULL;
gc_globals->unused = GC_INVALID;
gc_globals->first_unused = GC_INVALID;
gc_globals->gc_threshold = GC_INVALID;
gc_globals->buf_size = GC_INVALID;
gc_globals->num_roots = 0;
gc_globals->gc_runs = 0;
gc_globals->collected = 0;
#if GC_BENCH
gc_globals->root_buf_length = 0;
gc_globals->root_buf_peak = 0;
gc_globals->zval_possible_root = 0;
gc_globals->zval_buffered = 0;
gc_globals->zval_remove_from_buffer = 0;
gc_globals->zval_marked_grey = 0;
#endif
}
void gc_globals_ctor(void)
{
#ifdef ZTS
ts_allocate_fast_id(&gc_globals_id, &gc_globals_offset, sizeof(zend_gc_globals), (ts_allocate_ctor) gc_globals_ctor_ex, (ts_allocate_dtor) root_buffer_dtor);
#else
gc_globals_ctor_ex(&gc_globals);
#endif
}
void gc_globals_dtor(void)
{
#ifndef ZTS
root_buffer_dtor(&gc_globals);
#endif
}
void gc_reset(void)
{
if (GC_G(buf)) {
GC_G(gc_active) = 0;
GC_G(gc_protected) = 0;
GC_G(gc_full) = 0;
GC_G(unused) = GC_INVALID;
GC_G(first_unused) = GC_FIRST_ROOT;
GC_G(num_roots) = 0;
GC_G(gc_runs) = 0;
GC_G(collected) = 0;
#if GC_BENCH
GC_G(root_buf_length) = 0;
GC_G(root_buf_peak) = 0;
GC_G(zval_possible_root) = 0;
GC_G(zval_buffered) = 0;
GC_G(zval_remove_from_buffer) = 0;
GC_G(zval_marked_grey) = 0;
#endif
}
}
ZEND_API bool gc_enable(bool enable)
{
bool old_enabled = GC_G(gc_enabled);
GC_G(gc_enabled) = enable;
if (enable && !old_enabled && GC_G(buf) == NULL) {
GC_G(buf) = (gc_root_buffer*) pemalloc(sizeof(gc_root_buffer) * GC_DEFAULT_BUF_SIZE, 1);
GC_G(buf)[0].ref = NULL;
GC_G(buf_size) = GC_DEFAULT_BUF_SIZE;
GC_G(gc_threshold) = GC_THRESHOLD_DEFAULT;
gc_reset();
}
return old_enabled;
}
ZEND_API bool gc_enabled(void)
{
return GC_G(gc_enabled);
}
ZEND_API bool gc_protect(bool protect)
{
bool old_protected = GC_G(gc_protected);
GC_G(gc_protected) = protect;
return old_protected;
}
ZEND_API bool gc_protected(void)
{
return GC_G(gc_protected);
}
static void gc_grow_root_buffer(void)
{
size_t new_size;
if (GC_G(buf_size) >= GC_MAX_BUF_SIZE) {
if (!GC_G(gc_full)) {
zend_error(E_WARNING, "GC buffer overflow (GC disabled)\n");
GC_G(gc_active) = 1;
GC_G(gc_protected) = 1;
GC_G(gc_full) = 1;
return;
}
}
if (GC_G(buf_size) < GC_BUF_GROW_STEP) {
new_size = GC_G(buf_size) * 2;
} else {
new_size = GC_G(buf_size) + GC_BUF_GROW_STEP;
}
if (new_size > GC_MAX_BUF_SIZE) {
new_size = GC_MAX_BUF_SIZE;
}
GC_G(buf) = perealloc(GC_G(buf), sizeof(gc_root_buffer) * new_size, 1);
GC_G(buf_size) = new_size;
}
static void gc_adjust_threshold(int count)
{
uint32_t new_threshold;
/* TODO Very simple heuristic for dynamic GC buffer resizing:
* If there are "too few" collections, increase the collection threshold
* by a fixed step */
if (count < GC_THRESHOLD_TRIGGER || GC_G(num_roots) >= GC_G(gc_threshold)) {
/* increase */
if (GC_G(gc_threshold) < GC_THRESHOLD_MAX) {
new_threshold = GC_G(gc_threshold) + GC_THRESHOLD_STEP;
if (new_threshold > GC_THRESHOLD_MAX) {
new_threshold = GC_THRESHOLD_MAX;
}
if (new_threshold > GC_G(buf_size)) {
gc_grow_root_buffer();
}
if (new_threshold <= GC_G(buf_size)) {
GC_G(gc_threshold) = new_threshold;
}
}
} else if (GC_G(gc_threshold) > GC_THRESHOLD_DEFAULT) {
new_threshold = GC_G(gc_threshold) - GC_THRESHOLD_STEP;
if (new_threshold < GC_THRESHOLD_DEFAULT) {
new_threshold = GC_THRESHOLD_DEFAULT;
}
GC_G(gc_threshold) = new_threshold;
}
}
static zend_never_inline void ZEND_FASTCALL gc_possible_root_when_full(zend_refcounted *ref)
{
uint32_t idx;
gc_root_buffer *newRoot;
ZEND_ASSERT(GC_TYPE(ref) == IS_ARRAY || GC_TYPE(ref) == IS_OBJECT);
ZEND_ASSERT(GC_INFO(ref) == 0);
if (GC_G(gc_enabled) && !GC_G(gc_active)) {
GC_ADDREF(ref);
gc_adjust_threshold(gc_collect_cycles());
if (UNEXPECTED(GC_DELREF(ref)) == 0) {
rc_dtor_func(ref);
return;
} else if (UNEXPECTED(GC_INFO(ref))) {
return;
}
}
if (GC_HAS_UNUSED()) {
idx = GC_FETCH_UNUSED();
} else if (EXPECTED(GC_HAS_NEXT_UNUSED())) {
idx = GC_FETCH_NEXT_UNUSED();
} else {
gc_grow_root_buffer();
if (UNEXPECTED(!GC_HAS_NEXT_UNUSED())) {
return;
}
idx = GC_FETCH_NEXT_UNUSED();
}
newRoot = GC_IDX2PTR(idx);
newRoot->ref = ref; /* GC_ROOT tag is 0 */
GC_TRACE_SET_COLOR(ref, GC_PURPLE);
idx = gc_compress(idx);
GC_REF_SET_INFO(ref, idx | GC_PURPLE);
GC_G(num_roots)++;
GC_BENCH_INC(zval_buffered);
GC_BENCH_INC(root_buf_length);
GC_BENCH_PEAK(root_buf_peak, root_buf_length);
}
ZEND_API void ZEND_FASTCALL gc_possible_root(zend_refcounted *ref)
{
uint32_t idx;
gc_root_buffer *newRoot;
if (UNEXPECTED(GC_G(gc_protected))) {
return;
}
GC_BENCH_INC(zval_possible_root);
if (EXPECTED(GC_HAS_UNUSED())) {
idx = GC_FETCH_UNUSED();
} else if (EXPECTED(GC_HAS_NEXT_UNUSED_UNDER_THRESHOLD())) {
idx = GC_FETCH_NEXT_UNUSED();
} else {
gc_possible_root_when_full(ref);
return;
}
ZEND_ASSERT(GC_TYPE(ref) == IS_ARRAY || GC_TYPE(ref) == IS_OBJECT);
ZEND_ASSERT(GC_INFO(ref) == 0);
newRoot = GC_IDX2PTR(idx);
newRoot->ref = ref; /* GC_ROOT tag is 0 */
GC_TRACE_SET_COLOR(ref, GC_PURPLE);
idx = gc_compress(idx);
GC_REF_SET_INFO(ref, idx | GC_PURPLE);
GC_G(num_roots)++;
GC_BENCH_INC(zval_buffered);
GC_BENCH_INC(root_buf_length);
GC_BENCH_PEAK(root_buf_peak, root_buf_length);
}
static zend_never_inline void ZEND_FASTCALL gc_remove_compressed(zend_refcounted *ref, uint32_t idx)
{
gc_root_buffer *root = gc_decompress(ref, idx);
gc_remove_from_roots(root);
}
ZEND_API void ZEND_FASTCALL gc_remove_from_buffer(zend_refcounted *ref)
{
gc_root_buffer *root;
uint32_t idx = GC_REF_ADDRESS(ref);
GC_BENCH_INC(zval_remove_from_buffer);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_TRACE_SET_COLOR(ref, GC_BLACK);
}
GC_REF_SET_INFO(ref, 0);
/* Perform decompression only in case of large buffers */
if (UNEXPECTED(GC_G(first_unused) >= GC_MAX_UNCOMPRESSED)) {
gc_remove_compressed(ref, idx);
return;
}
ZEND_ASSERT(idx);
root = GC_IDX2PTR(idx);
gc_remove_from_roots(root);
}
static void gc_scan_black(zend_refcounted *ref, gc_stack *stack)
{
HashTable *ht;
Bucket *p;
zval *zv;
uint32_t n;
GC_STACK_DCL(stack);
tail_call:
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED))) {
zval *table;
int len;
ht = obj->handlers->get_gc(obj, &table, &len);
n = len;
zv = table;
if (UNEXPECTED(ht)) {
GC_ADDREF(ht);
if (!GC_REF_CHECK_COLOR(ht, GC_BLACK)) {
GC_REF_SET_BLACK(ht);
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto handle_ht;
}
}
handle_zvals:
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
zv++;
while (--n) {
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto tail_call;
}
}
zv++;
}
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
ZEND_ASSERT((zend_array*)ref != &EG(symbol_table));
ht = (zend_array*)ref;
handle_ht:
n = ht->nNumUsed;
zv = ht->arPacked;
if (HT_IS_PACKED(ht)) {
goto handle_zvals;
}
p = (Bucket*)zv;
for (; n != 0; n--) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
p++;
while (--n) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
p++;
}
goto tail_call;
}
}
p++;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
goto tail_call;
}
}
}
ref = GC_STACK_POP();
if (ref) {
goto tail_call;
}
}
static void gc_mark_grey(zend_refcounted *ref, gc_stack *stack)
{
HashTable *ht;
Bucket *p;
zval *zv;
uint32_t n;
GC_STACK_DCL(stack);
tail_call:
GC_BENCH_INC(zval_marked_grey);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED))) {
zval *table;
int len;
ht = obj->handlers->get_gc(obj, &table, &len);
n = len;
zv = table;
if (UNEXPECTED(ht)) {
GC_DELREF(ht);
if (!GC_REF_CHECK_COLOR(ht, GC_GREY)) {
GC_REF_SET_COLOR(ht, GC_GREY);
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto handle_ht;
}
}
handle_zvals:
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
zv++;
while (--n) {
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto tail_call;
}
}
zv++;
}
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
ZEND_ASSERT(((zend_array*)ref) != &EG(symbol_table));
ht = (zend_array*)ref;
handle_ht:
n = ht->nNumUsed;
if (HT_IS_PACKED(ht)) {
zv = ht->arPacked;
goto handle_zvals;
}
p = ht->arData;
for (; n != 0; n--) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
p++;
while (--n) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
GC_STACK_PUSH(ref);
}
}
p++;
}
goto tail_call;
}
}
p++;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_DELREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_GREY);
goto tail_call;
}
}
}
ref = GC_STACK_POP();
if (ref) {
goto tail_call;
}
}
/* Two-Finger compaction algorithm */
static void gc_compact(void)
{
if (GC_G(num_roots) + GC_FIRST_ROOT != GC_G(first_unused)) {
if (GC_G(num_roots)) {
gc_root_buffer *free = GC_IDX2PTR(GC_FIRST_ROOT);
gc_root_buffer *scan = GC_IDX2PTR(GC_G(first_unused) - 1);
gc_root_buffer *end = GC_IDX2PTR(GC_G(num_roots));
uint32_t idx;
zend_refcounted *p;
while (free < scan) {
while (!GC_IS_UNUSED(free->ref)) {
free++;
}
while (GC_IS_UNUSED(scan->ref)) {
scan--;
}
if (scan > free) {
p = scan->ref;
free->ref = p;
p = GC_GET_PTR(p);
idx = gc_compress(GC_PTR2IDX(free));
GC_REF_SET_INFO(p, idx | GC_REF_COLOR(p));
free++;
scan--;
if (scan <= end) {
break;
}
}
}
}
GC_G(unused) = GC_INVALID;
GC_G(first_unused) = GC_G(num_roots) + GC_FIRST_ROOT;
}
}
static void gc_mark_roots(gc_stack *stack)
{
gc_root_buffer *current, *last;
gc_compact();
current = GC_IDX2PTR(GC_FIRST_ROOT);
last = GC_IDX2PTR(GC_G(first_unused));
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_CHECK_COLOR(current->ref, GC_PURPLE)) {
GC_REF_SET_COLOR(current->ref, GC_GREY);
gc_mark_grey(current->ref, stack);
}
}
current++;
}
}
static void gc_scan(zend_refcounted *ref, gc_stack *stack)
{
HashTable *ht;
Bucket *p;
zval *zv;
uint32_t n;
GC_STACK_DCL(stack);
tail_call:
if (!GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
goto next;
}
if (GC_REFCOUNT(ref) > 0) {
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_REF_SET_BLACK(ref);
if (UNEXPECTED(!_stack->next)) {
gc_stack_next(_stack);
}
/* Split stack and reuse the tail */
_stack->next->prev = NULL;
gc_scan_black(ref, _stack->next);
_stack->next->prev = _stack;
}
goto next;
}
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED))) {
zval *table;
int len;
ht = obj->handlers->get_gc(obj, &table, &len);
n = len;
zv = table;
if (UNEXPECTED(ht)) {
if (GC_REF_CHECK_COLOR(ht, GC_GREY)) {
GC_REF_SET_COLOR(ht, GC_WHITE);
GC_STACK_PUSH((zend_refcounted *) ht);
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto handle_ht;
}
}
handle_zvals:
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
zv++;
while (--n) {
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto tail_call;
}
}
zv++;
}
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
ht = (HashTable *)ref;
ZEND_ASSERT(ht != &EG(symbol_table));
handle_ht:
n = ht->nNumUsed;
if (HT_IS_PACKED(ht)) {
zv = ht->arPacked;
goto handle_zvals;
}
p = ht->arData;
for (; n != 0; n--) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
p++;
while (--n) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
GC_STACK_PUSH(ref);
}
}
p++;
}
goto tail_call;
}
}
p++;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
GC_REF_SET_COLOR(ref, GC_WHITE);
goto tail_call;
}
}
}
next:
ref = GC_STACK_POP();
if (ref) {
goto tail_call;
}
}
static void gc_scan_roots(gc_stack *stack)
{
gc_root_buffer *current = GC_IDX2PTR(GC_FIRST_ROOT);
gc_root_buffer *last = GC_IDX2PTR(GC_G(first_unused));
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_CHECK_COLOR(current->ref, GC_GREY)) {
GC_REF_SET_COLOR(current->ref, GC_WHITE);
gc_scan(current->ref, stack);
}
}
current++;
}
}
static void gc_add_garbage(zend_refcounted *ref)
{
uint32_t idx;
gc_root_buffer *buf;
if (GC_HAS_UNUSED()) {
idx = GC_FETCH_UNUSED();
} else if (GC_HAS_NEXT_UNUSED()) {
idx = GC_FETCH_NEXT_UNUSED();
} else {
gc_grow_root_buffer();
if (UNEXPECTED(!GC_HAS_NEXT_UNUSED())) {
return;
}
idx = GC_FETCH_NEXT_UNUSED();
}
buf = GC_IDX2PTR(idx);
buf->ref = GC_MAKE_GARBAGE(ref);
idx = gc_compress(idx);
GC_REF_SET_INFO(ref, idx | GC_BLACK);
GC_G(num_roots)++;
}
static int gc_collect_white(zend_refcounted *ref, uint32_t *flags, gc_stack *stack)
{
int count = 0;
HashTable *ht;
Bucket *p;
zval *zv;
uint32_t n;
GC_STACK_DCL(stack);
tail_call:
/* don't count references for compatibility ??? */
if (GC_TYPE(ref) != IS_REFERENCE) {
count++;
}
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED))) {
int len;
zval *table;
/* optimization: color is GC_BLACK (0) */
if (!GC_INFO(ref)) {
gc_add_garbage(ref);
}
if (!(OBJ_FLAGS(obj) & IS_OBJ_DESTRUCTOR_CALLED)
&& (obj->handlers->dtor_obj != zend_objects_destroy_object
|| obj->ce->destructor != NULL)) {
*flags |= GC_HAS_DESTRUCTORS;
}
ht = obj->handlers->get_gc(obj, &table, &len);
n = len;
zv = table;
if (UNEXPECTED(ht)) {
GC_ADDREF(ht);
if (GC_REF_CHECK_COLOR(ht, GC_WHITE)) {
GC_REF_SET_BLACK(ht);
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto handle_ht;
}
}
handle_zvals:
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
zv++;
while (--n) {
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
zv++;
}
goto tail_call;
}
}
zv++;
}
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
/* optimization: color is GC_BLACK (0) */
if (!GC_INFO(ref)) {
gc_add_garbage(ref);
}
ht = (zend_array*)ref;
handle_ht:
n = ht->nNumUsed;
if (HT_IS_PACKED(ht)) {
zv = ht->arPacked;
goto handle_zvals;
}
p = ht->arData;
for (; n != 0; n--) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
p++;
while (--n) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
GC_STACK_PUSH(ref);
}
}
p++;
}
goto tail_call;
}
}
p++;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
goto tail_call;
}
}
}
ref = GC_STACK_POP();
if (ref) {
goto tail_call;
}
return count;
}
static int gc_collect_roots(uint32_t *flags, gc_stack *stack)
{
uint32_t idx, end;
zend_refcounted *ref;
int count = 0;
gc_root_buffer *current = GC_IDX2PTR(GC_FIRST_ROOT);
gc_root_buffer *last = GC_IDX2PTR(GC_G(first_unused));
/* remove non-garbage from the list */
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_CHECK_COLOR(current->ref, GC_BLACK)) {
GC_REF_SET_INFO(current->ref, 0); /* reset GC_ADDRESS() and keep GC_BLACK */
gc_remove_from_roots(current);
}
}
current++;
}
gc_compact();
/* Root buffer might be reallocated during gc_collect_white,
* make sure to reload pointers. */
idx = GC_FIRST_ROOT;
end = GC_G(first_unused);
while (idx != end) {
current = GC_IDX2PTR(idx);
ref = current->ref;
ZEND_ASSERT(GC_IS_ROOT(ref));
current->ref = GC_MAKE_GARBAGE(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
GC_REF_SET_BLACK(ref);
count += gc_collect_white(ref, flags, stack);
}
idx++;
}
return count;
}
static int gc_remove_nested_data_from_buffer(zend_refcounted *ref, gc_root_buffer *root, gc_stack *stack)
{
HashTable *ht;
Bucket *p;
zval *zv;
uint32_t n;
int count = 0;
GC_STACK_DCL(stack);
tail_call:
if (root) {
root = NULL;
count++;
} else if (GC_REF_ADDRESS(ref) != 0
&& GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
GC_TRACE_REF(ref, "removing from buffer");
GC_REMOVE_FROM_BUFFER(ref);
count++;
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
goto tail_call;
}
goto next;
} else {
goto next;
}
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
if (EXPECTED(!(OBJ_FLAGS(ref) & IS_OBJ_FREE_CALLED))) {
int len;
zval *table;
ht = obj->handlers->get_gc(obj, &table, &len);
n = len;
zv = table;
if (UNEXPECTED(ht)) {
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_STACK_PUSH(ref);
}
zv++;
}
if (GC_REF_ADDRESS(ht) != 0 && GC_REF_CHECK_COLOR(ht, GC_BLACK)) {
GC_TRACE_REF(ht, "removing from buffer");
GC_REMOVE_FROM_BUFFER(ht);
}
goto handle_ht;
}
handle_zvals:
for (; n != 0; n--) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
zv++;
while (--n) {
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_STACK_PUSH(ref);
}
zv++;
}
goto tail_call;
}
zv++;
}
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
ht = (zend_array*)ref;
handle_ht:
n = ht->nNumUsed;
if (HT_IS_PACKED(ht)) {
zv = ht->arPacked;
goto handle_zvals;
}
p = ht->arData;
for (; n != 0; n--) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
p++;
while (--n) {
zv = &p->val;
if (Z_TYPE_P(zv) == IS_INDIRECT) {
zv = Z_INDIRECT_P(zv);
}
if (Z_REFCOUNTED_P(zv)) {
zend_refcounted *ref = Z_COUNTED_P(zv);
GC_STACK_PUSH(ref);
}
p++;
}
goto tail_call;
}
p++;
}
}
next:
ref = GC_STACK_POP();
if (ref) {
goto tail_call;
}
return count;
}
static void zend_get_gc_buffer_release(void);
static void zend_gc_check_root_tmpvars(void);
static void zend_gc_remove_root_tmpvars(void);
ZEND_API int zend_gc_collect_cycles(void)
{
int total_count = 0;
bool should_rerun_gc = 0;
bool did_rerun_gc = 0;
if (GC_G(num_roots) && GC_G(gc_active)) {
zend_gc_remove_root_tmpvars();
}
rerun_gc:
if (GC_G(num_roots)) {
int count;
gc_root_buffer *current, *last;
zend_refcounted *p;
uint32_t gc_flags = 0;
uint32_t idx, end;
gc_stack stack;
stack.prev = NULL;
stack.next = NULL;
if (GC_G(gc_active)) {
return 0;
}
GC_TRACE("Collecting cycles");
GC_G(gc_runs)++;
GC_G(gc_active) = 1;
GC_TRACE("Marking roots");
gc_mark_roots(&stack);
GC_TRACE("Scanning roots");
gc_scan_roots(&stack);
GC_TRACE("Collecting roots");
count = gc_collect_roots(&gc_flags, &stack);
if (!GC_G(num_roots)) {
/* nothing to free */
GC_TRACE("Nothing to free");
gc_stack_free(&stack);
GC_G(gc_active) = 0;
goto finish;
}
zend_fiber_switch_block();
end = GC_G(first_unused);
if (gc_flags & GC_HAS_DESTRUCTORS) {
GC_TRACE("Calling destructors");
/* During a destructor call, new externally visible references to nested data may
* be introduced. These references can be introduced in a way that does not
* modify any refcounts, so we have no real way to detect this situation
* short of rerunning full GC tracing. What we do instead is to only run
* destructors at this point and automatically re-run GC afterwards. */
should_rerun_gc = 1;
/* Mark all roots for which a dtor will be invoked as DTOR_GARBAGE. Additionally
* color them purple. This serves a double purpose: First, they should be
* considered new potential roots for the next GC run. Second, it will prevent
* their removal from the root buffer by nested data removal. */
idx = GC_FIRST_ROOT;
current = GC_IDX2PTR(GC_FIRST_ROOT);
while (idx != end) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
if (GC_TYPE(p) == IS_OBJECT && !(OBJ_FLAGS(p) & IS_OBJ_DESTRUCTOR_CALLED)) {
zend_object *obj = (zend_object *) p;
if (obj->handlers->dtor_obj != zend_objects_destroy_object
|| obj->ce->destructor) {
current->ref = GC_MAKE_DTOR_GARBAGE(obj);
GC_REF_SET_COLOR(obj, GC_PURPLE);
} else {
GC_ADD_FLAGS(obj, IS_OBJ_DESTRUCTOR_CALLED);
}
}
}
current++;
idx++;
}
/* Remove nested data for objects on which a destructor will be called.
* This will not remove the objects themselves, as they have been colored
* purple. */
idx = GC_FIRST_ROOT;
current = GC_IDX2PTR(GC_FIRST_ROOT);
while (idx != end) {
if (GC_IS_DTOR_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
count -= gc_remove_nested_data_from_buffer(p, current, &stack);
}
current++;
idx++;
}
/* Actually call destructors.
*
* The root buffer might be reallocated during destructors calls,
* make sure to reload pointers as necessary. */
idx = GC_FIRST_ROOT;
while (idx != end) {
current = GC_IDX2PTR(idx);
if (GC_IS_DTOR_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
/* Mark this is as a normal root for the next GC run,
* it's no longer garbage for this run. */
current->ref = p;
/* Double check that the destructor hasn't been called yet. It could have
* already been invoked indirectly by some other destructor. */
if (!(OBJ_FLAGS(p) & IS_OBJ_DESTRUCTOR_CALLED)) {
zend_object *obj = (zend_object*)p;
GC_TRACE_REF(obj, "calling destructor");
GC_ADD_FLAGS(obj, IS_OBJ_DESTRUCTOR_CALLED);
GC_ADDREF(obj);
obj->handlers->dtor_obj(obj);
GC_DELREF(obj);
}
}
idx++;
}
if (GC_G(gc_protected)) {
/* something went wrong */
zend_get_gc_buffer_release();
zend_fiber_switch_unblock();
return 0;
}
}
gc_stack_free(&stack);
/* Destroy zvals. The root buffer may be reallocated. */
GC_TRACE("Destroying zvals");
idx = GC_FIRST_ROOT;
while (idx != end) {
current = GC_IDX2PTR(idx);
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
GC_TRACE_REF(p, "destroying");
if (GC_TYPE(p) == IS_OBJECT) {
zend_object *obj = (zend_object*)p;
EG(objects_store).object_buckets[obj->handle] = SET_OBJ_INVALID(obj);
GC_TYPE_INFO(obj) = GC_NULL |
(GC_TYPE_INFO(obj) & ~GC_TYPE_MASK);
/* Modify current before calling free_obj (bug #78811: free_obj() can cause the root buffer (with current) to be reallocated.) */
current->ref = GC_MAKE_GARBAGE(((char*)obj) - obj->handlers->offset);
if (!(OBJ_FLAGS(obj) & IS_OBJ_FREE_CALLED)) {
GC_ADD_FLAGS(obj, IS_OBJ_FREE_CALLED);
GC_ADDREF(obj);
obj->handlers->free_obj(obj);
GC_DELREF(obj);
}
ZEND_OBJECTS_STORE_ADD_TO_FREE_LIST(obj->handle);
} else if (GC_TYPE(p) == IS_ARRAY) {
zend_array *arr = (zend_array*)p;
GC_TYPE_INFO(arr) = GC_NULL |
(GC_TYPE_INFO(arr) & ~GC_TYPE_MASK);
/* GC may destroy arrays with rc>1. This is valid and safe. */
HT_ALLOW_COW_VIOLATION(arr);
zend_hash_destroy(arr);
}
}
idx++;
}
/* Free objects */
current = GC_IDX2PTR(GC_FIRST_ROOT);
last = GC_IDX2PTR(end);
while (current != last) {
if (GC_IS_GARBAGE(current->ref)) {
p = GC_GET_PTR(current->ref);
GC_LINK_UNUSED(current);
GC_G(num_roots)--;
efree(p);
}
current++;
}
zend_fiber_switch_unblock();
GC_TRACE("Collection finished");
GC_G(collected) += count;
total_count += count;
GC_G(gc_active) = 0;
}
gc_compact();
/* Objects with destructors were removed from this GC run. Rerun GC right away to clean them
* up. We do this only once: If we encounter more destructors on the second run, we'll not
* run GC another time. */
if (should_rerun_gc && !did_rerun_gc) {
did_rerun_gc = 1;
goto rerun_gc;
}
finish:
zend_get_gc_buffer_release();
/* Prevent GC from running during zend_gc_check_root_tmpvars, before
* gc_threshold is adjusted, as this may result in unbounded recursion */
GC_G(gc_active) = 1;
zend_gc_check_root_tmpvars();
GC_G(gc_active) = 0;
return total_count;
}
ZEND_API void zend_gc_get_status(zend_gc_status *status)
{
status->runs = GC_G(gc_runs);
status->collected = GC_G(collected);
status->threshold = GC_G(gc_threshold);
status->num_roots = GC_G(num_roots);
}
ZEND_API zend_get_gc_buffer *zend_get_gc_buffer_create(void) {
/* There can only be one get_gc() call active at a time,
* so there only needs to be one buffer. */
zend_get_gc_buffer *gc_buffer = &EG(get_gc_buffer);
gc_buffer->cur = gc_buffer->start;
return gc_buffer;
}
ZEND_API void zend_get_gc_buffer_grow(zend_get_gc_buffer *gc_buffer) {
size_t old_capacity = gc_buffer->end - gc_buffer->start;
size_t new_capacity = old_capacity == 0 ? 64 : old_capacity * 2;
gc_buffer->start = erealloc(gc_buffer->start, new_capacity * sizeof(zval));
gc_buffer->end = gc_buffer->start + new_capacity;
gc_buffer->cur = gc_buffer->start + old_capacity;
}
static void zend_get_gc_buffer_release(void) {
zend_get_gc_buffer *gc_buffer = &EG(get_gc_buffer);
efree(gc_buffer->start);
gc_buffer->start = gc_buffer->end = gc_buffer->cur = NULL;
}
/* TMPVAR operands are destroyed using zval_ptr_dtor_nogc(), because they usually cannot contain
* cycles. However, there are some rare exceptions where this is possible, in which case we rely
* on the producing code to root the value. If a GC run occurs between the rooting and consumption
* of the value, we would end up leaking it. To avoid this, root all live TMPVAR values here. */
static void zend_gc_check_root_tmpvars(void) {
zend_execute_data *ex = EG(current_execute_data);
for (; ex; ex = ex->prev_execute_data) {
zend_function *func = ex->func;
if (!func || !ZEND_USER_CODE(func->type)) {
continue;
}
uint32_t op_num = ex->opline - ex->func->op_array.opcodes;
for (uint32_t i = 0; i < func->op_array.last_live_range; i++) {
const zend_live_range *range = &func->op_array.live_range[i];
if (range->start > op_num) {
break;
}
if (range->end <= op_num) {
continue;
}
uint32_t kind = range->var & ZEND_LIVE_MASK;
if (kind == ZEND_LIVE_TMPVAR || kind == ZEND_LIVE_LOOP) {
uint32_t var_num = range->var & ~ZEND_LIVE_MASK;
zval *var = ZEND_CALL_VAR(ex, var_num);
if (Z_REFCOUNTED_P(var)) {
gc_check_possible_root(Z_COUNTED_P(var));
}
}
}
}
}
static void zend_gc_remove_root_tmpvars(void) {
zend_execute_data *ex = EG(current_execute_data);
for (; ex; ex = ex->prev_execute_data) {
zend_function *func = ex->func;
if (!func || !ZEND_USER_CODE(func->type)) {
continue;
}
uint32_t op_num = ex->opline - ex->func->op_array.opcodes;
for (uint32_t i = 0; i < func->op_array.last_live_range; i++) {
const zend_live_range *range = &func->op_array.live_range[i];
if (range->start > op_num) {
break;
}
if (range->end <= op_num) {
continue;
}
uint32_t kind = range->var & ZEND_LIVE_MASK;
if (kind == ZEND_LIVE_TMPVAR || kind == ZEND_LIVE_LOOP) {
uint32_t var_num = range->var & ~ZEND_LIVE_MASK;
zval *var = ZEND_CALL_VAR(ex, var_num);
if (Z_REFCOUNTED_P(var)) {
GC_REMOVE_FROM_BUFFER(Z_COUNTED_P(var));
}
}
}
}
}
#ifdef ZTS
size_t zend_gc_globals_size(void)
{
return sizeof(zend_gc_globals);
}
#endif
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