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ruby--ruby/shape.h
Jemma Issroff 913979bede
Make inline cache reads / writes atomic with object shapes
Prior to this commit, we were reading and writing ivar index and
shape ID in inline caches in two separate instructions when
getting and setting ivars. This meant there was a race condition
with ractors and these caches where one ractor could change
a value in the cache while another was still reading from it.

This commit instead reads and writes shape ID and ivar index to
inline caches atomically so there is no longer a race condition.

Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Co-Authored-By: John Hawthorn <john@hawthorn.email>
2022-10-11 08:40:56 -07:00

136 lines
3.6 KiB
C

#ifndef RUBY_SHAPE_H
#define RUBY_SHAPE_H
#if (SIZEOF_UINT64_T == SIZEOF_VALUE)
#define SIZEOF_SHAPE_T 4
#define SHAPE_IN_BASIC_FLAGS 1
typedef uint32_t attr_index_t;
#else
#define SIZEOF_SHAPE_T 2
#define SHAPE_IN_BASIC_FLAGS 0
typedef uint16_t attr_index_t;
#endif
#define MAX_IVARS (attr_index_t)(-1)
#if RUBY_DEBUG || (defined(VM_CHECK_MODE) && VM_CHECK_MODE > 0)
# if SIZEOF_SHAPE_T == 4
typedef uint32_t shape_id_t;
# define SHAPE_BITS 16
# else
typedef uint16_t shape_id_t;
# define SHAPE_BITS 16
# endif
#else
# if SIZEOF_SHAPE_T == 4
typedef uint32_t shape_id_t;
# define SHAPE_BITS 32
# else
typedef uint16_t shape_id_t;
# define SHAPE_BITS 16
# endif
#endif
# define SHAPE_MASK (((uintptr_t)1 << SHAPE_BITS) - 1)
# define SHAPE_FLAG_MASK (((VALUE)-1) >> SHAPE_BITS)
# define SHAPE_FLAG_SHIFT ((SIZEOF_VALUE * 8) - SHAPE_BITS)
# define SHAPE_BITMAP_SIZE 16384
# define MAX_SHAPE_ID (SHAPE_MASK - 1)
# define INVALID_SHAPE_ID SHAPE_MASK
# define ROOT_SHAPE_ID 0x0
# define FROZEN_ROOT_SHAPE_ID 0x1
struct rb_shape {
struct rb_id_table * edges; // id_table from ID (ivar) to next shape
ID edge_name; // ID (ivar) for transition from parent to rb_shape
attr_index_t iv_count;
uint8_t type;
shape_id_t parent_id;
};
typedef struct rb_shape rb_shape_t;
enum shape_type {
SHAPE_ROOT,
SHAPE_IVAR,
SHAPE_FROZEN,
SHAPE_IVAR_UNDEF,
};
#if SHAPE_IN_BASIC_FLAGS
static inline shape_id_t
RBASIC_SHAPE_ID(VALUE obj)
{
RUBY_ASSERT(!RB_SPECIAL_CONST_P(obj));
return (shape_id_t)(SHAPE_MASK & ((RBASIC(obj)->flags) >> SHAPE_FLAG_SHIFT));
}
static inline void
RBASIC_SET_SHAPE_ID(VALUE obj, shape_id_t shape_id)
{
// Ractors are occupying the upper 32 bits of flags, but only in debug mode
// Object shapes are occupying top bits
RBASIC(obj)->flags &= SHAPE_FLAG_MASK;
RBASIC(obj)->flags |= ((VALUE)(shape_id) << SHAPE_FLAG_SHIFT);
}
static inline shape_id_t
ROBJECT_SHAPE_ID(VALUE obj)
{
RBIMPL_ASSERT_TYPE(obj, RUBY_T_OBJECT);
return RBASIC_SHAPE_ID(obj);
}
static inline void
ROBJECT_SET_SHAPE_ID(VALUE obj, shape_id_t shape_id)
{
RBIMPL_ASSERT_TYPE(obj, RUBY_T_OBJECT);
RBASIC_SET_SHAPE_ID(obj, shape_id);
}
#else
static inline shape_id_t
ROBJECT_SHAPE_ID(VALUE obj)
{
RBIMPL_ASSERT_TYPE(obj, RUBY_T_OBJECT);
return (shape_id_t)(SHAPE_MASK & (RBASIC(obj)->flags >> SHAPE_FLAG_SHIFT));
}
static inline void
ROBJECT_SET_SHAPE_ID(VALUE obj, shape_id_t shape_id)
{
RBASIC(obj)->flags &= SHAPE_FLAG_MASK;
RBASIC(obj)->flags |= ((VALUE)(shape_id) << SHAPE_FLAG_SHIFT);
}
#endif
bool rb_shape_root_shape_p(rb_shape_t* shape);
rb_shape_t* rb_shape_get_shape_by_id_without_assertion(shape_id_t shape_id);
MJIT_SYMBOL_EXPORT_BEGIN
rb_shape_t* rb_shape_get_shape_by_id(shape_id_t shape_id);
void rb_shape_set_shape(VALUE obj, rb_shape_t* shape);
shape_id_t rb_shape_get_shape_id(VALUE obj);
rb_shape_t* rb_shape_get_shape(VALUE obj);
int rb_shape_frozen_shape_p(rb_shape_t* shape);
void rb_shape_transition_shape_frozen(VALUE obj);
void rb_shape_transition_shape_remove_ivar(VALUE obj, ID id, rb_shape_t *shape);
void rb_shape_transition_shape(VALUE obj, ID id, rb_shape_t *shape);
rb_shape_t* rb_shape_get_next(rb_shape_t* shape, VALUE obj, ID id);
bool rb_shape_get_iv_index(rb_shape_t * shape, ID id, attr_index_t * value);
shape_id_t rb_shape_id(rb_shape_t * shape);
MJIT_SYMBOL_EXPORT_END
rb_shape_t * rb_shape_alloc(ID edge_name, rb_shape_t * parent);
rb_shape_t * rb_shape_alloc_with_parent_id(ID edge_name, shape_id_t parent_id);
bool rb_shape_set_shape_id(VALUE obj, shape_id_t shape_id);
VALUE rb_obj_debug_shape(VALUE self, VALUE obj);
VALUE rb_shape_flags_mask(void);
#endif