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Ruby: Implement Write Barriers (#11793)
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Write barrier protected objects are allowed to be promoted to the old generation, which means they only get marked on major GC.

The downside is that the `RB_BJ_WRITE` macro MUST be used to set references, otherwise the referenced object may be garbaged collected.

But the `*Descriptor` classes and `Arena` have very few references and are only set in a few places, so it's relatively easy to implement.

cc @peterzhu2118

Closes #11793

COPYBARA_INTEGRATE_REVIEW=#11793 from casperisfine:descriptor-write-barrier 215e8fa
PiperOrigin-RevId: 511875342
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@casperisfine @copybara-github
casperisfine authored and copybara-github committed Feb 23, 2023
1 parent 08c5557 commit d82d8a4
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Showing 3 changed files with 31 additions and 17 deletions.
34 changes: 22 additions & 12 deletions ruby/ext/google/protobuf_c/defs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -223,6 +223,8 @@ static void DescriptorPool_register(VALUE module) {

typedef struct {
const upb_MessageDef* msgdef;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE klass;
VALUE descriptor_pool;
} Descriptor;
Expand All @@ -238,7 +240,7 @@ static void Descriptor_mark(void* _self) {
static const rb_data_type_t Descriptor_type = {
"Google::Protobuf::Descriptor",
{Descriptor_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static Descriptor* ruby_to_Descriptor(VALUE val) {
Expand Down Expand Up @@ -280,7 +282,7 @@ static VALUE Descriptor_initialize(VALUE _self, VALUE cookie,
"Descriptor objects may not be created from Ruby.");
}

self->descriptor_pool = descriptor_pool;
RB_OBJ_WRITE(_self, &self->descriptor_pool, descriptor_pool);
self->msgdef = (const upb_MessageDef*)NUM2ULL(ptr);

return Qnil;
Expand Down Expand Up @@ -390,7 +392,7 @@ static VALUE Descriptor_lookup_oneof(VALUE _self, VALUE name) {
static VALUE Descriptor_msgclass(VALUE _self) {
Descriptor* self = ruby_to_Descriptor(_self);
if (self->klass == Qnil) {
self->klass = build_class_from_descriptor(_self);
RB_OBJ_WRITE(_self, &self->klass, build_class_from_descriptor(_self));
}
return self->klass;
}
Expand All @@ -417,6 +419,8 @@ static void Descriptor_register(VALUE module) {

typedef struct {
const upb_FileDef* filedef;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE descriptor_pool; // Owns the upb_FileDef.
} FileDescriptor;

Expand All @@ -430,7 +434,7 @@ static void FileDescriptor_mark(void* _self) {
static const rb_data_type_t FileDescriptor_type = {
"Google::Protobuf::FileDescriptor",
{FileDescriptor_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static FileDescriptor* ruby_to_FileDescriptor(VALUE val) {
Expand Down Expand Up @@ -463,7 +467,7 @@ static VALUE FileDescriptor_initialize(VALUE _self, VALUE cookie,
"Descriptor objects may not be created from Ruby.");
}

self->descriptor_pool = descriptor_pool;
RB_OBJ_WRITE(_self, &self->descriptor_pool, descriptor_pool);
self->filedef = (const upb_FileDef*)NUM2ULL(ptr);

return Qnil;
Expand Down Expand Up @@ -519,6 +523,8 @@ static void FileDescriptor_register(VALUE module) {

typedef struct {
const upb_FieldDef* fielddef;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE descriptor_pool; // Owns the upb_FieldDef.
} FieldDescriptor;

Expand All @@ -532,7 +538,7 @@ static void FieldDescriptor_mark(void* _self) {
static const rb_data_type_t FieldDescriptor_type = {
"Google::Protobuf::FieldDescriptor",
{FieldDescriptor_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static FieldDescriptor* ruby_to_FieldDescriptor(VALUE val) {
Expand Down Expand Up @@ -570,7 +576,7 @@ static VALUE FieldDescriptor_initialize(VALUE _self, VALUE cookie,
"Descriptor objects may not be created from Ruby.");
}

self->descriptor_pool = descriptor_pool;
RB_OBJ_WRITE(_self, &self->descriptor_pool, descriptor_pool);
self->fielddef = (const upb_FieldDef*)NUM2ULL(ptr);

return Qnil;
Expand Down Expand Up @@ -884,6 +890,8 @@ static void FieldDescriptor_register(VALUE module) {

typedef struct {
const upb_OneofDef* oneofdef;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE descriptor_pool; // Owns the upb_OneofDef.
} OneofDescriptor;

Expand All @@ -897,7 +905,7 @@ static void OneofDescriptor_mark(void* _self) {
static const rb_data_type_t OneofDescriptor_type = {
"Google::Protobuf::OneofDescriptor",
{OneofDescriptor_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static OneofDescriptor* ruby_to_OneofDescriptor(VALUE val) {
Expand Down Expand Up @@ -936,7 +944,7 @@ static VALUE OneofDescriptor_initialize(VALUE _self, VALUE cookie,
"Descriptor objects may not be created from Ruby.");
}

self->descriptor_pool = descriptor_pool;
RB_OBJ_WRITE(_self, &self->descriptor_pool, descriptor_pool);
self->oneofdef = (const upb_OneofDef*)NUM2ULL(ptr);

return Qnil;
Expand Down Expand Up @@ -988,6 +996,8 @@ static void OneofDescriptor_register(VALUE module) {

typedef struct {
const upb_EnumDef* enumdef;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE module; // begins as nil
VALUE descriptor_pool; // Owns the upb_EnumDef.
} EnumDescriptor;
Expand All @@ -1003,7 +1013,7 @@ static void EnumDescriptor_mark(void* _self) {
static const rb_data_type_t EnumDescriptor_type = {
"Google::Protobuf::EnumDescriptor",
{EnumDescriptor_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static EnumDescriptor* ruby_to_EnumDescriptor(VALUE val) {
Expand Down Expand Up @@ -1042,7 +1052,7 @@ static VALUE EnumDescriptor_initialize(VALUE _self, VALUE cookie,
"Descriptor objects may not be created from Ruby.");
}

self->descriptor_pool = descriptor_pool;
RB_OBJ_WRITE(_self, &self->descriptor_pool, descriptor_pool);
self->enumdef = (const upb_EnumDef*)NUM2ULL(ptr);

return Qnil;
Expand Down Expand Up @@ -1138,7 +1148,7 @@ static VALUE EnumDescriptor_each(VALUE _self) {
static VALUE EnumDescriptor_enummodule(VALUE _self) {
EnumDescriptor* self = ruby_to_EnumDescriptor(_self);
if (self->module == Qnil) {
self->module = build_module_from_enumdesc(_self);
RB_OBJ_WRITE(_self, &self->module, build_module_from_enumdesc(_self));
}
return self->module;
}
Expand Down
8 changes: 5 additions & 3 deletions ruby/ext/google/protobuf_c/message.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,8 @@ VALUE MessageOrEnum_GetDescriptor(VALUE klass) {
// -----------------------------------------------------------------------------

typedef struct {
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE arena;
const upb_Message* msg; // Can get as mutable when non-frozen.
const upb_MessageDef*
Expand All @@ -65,9 +67,9 @@ static void Message_mark(void* _self) {
}

static rb_data_type_t Message_type = {
"Message",
"Google::Protobuf::Message",
{Message_mark, RUBY_DEFAULT_FREE, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static Message* ruby_to_Message(VALUE msg_rb) {
Expand Down Expand Up @@ -105,7 +107,7 @@ upb_Message* Message_GetMutable(VALUE msg_rb, const upb_MessageDef** m) {
void Message_InitPtr(VALUE self_, upb_Message* msg, VALUE arena) {
Message* self = ruby_to_Message(self_);
self->msg = msg;
self->arena = arena;
RB_OBJ_WRITE(self_, &self->arena, arena);
ObjectCache_Add(msg, self_);
}

Expand Down
6 changes: 4 additions & 2 deletions ruby/ext/google/protobuf_c/protobuf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,8 @@ void StringBuilder_PrintMsgval(StringBuilder *b, upb_MessageValue val,

typedef struct {
upb_Arena *arena;
// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
// macro to update VALUE references, as to trigger write barriers.
VALUE pinned_objs;
} Arena;

Expand All @@ -190,7 +192,7 @@ static VALUE cArena;
const rb_data_type_t Arena_type = {
"Google::Protobuf::Internal::Arena",
{Arena_mark, Arena_free, NULL},
.flags = RUBY_TYPED_FREE_IMMEDIATELY,
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
};

static void* ruby_upb_allocfunc(upb_alloc* alloc, void* ptr, size_t oldsize, size_t size) {
Expand Down Expand Up @@ -233,7 +235,7 @@ void Arena_Pin(VALUE _arena, VALUE obj) {
Arena *arena;
TypedData_Get_Struct(_arena, Arena, &Arena_type, arena);
if (arena->pinned_objs == Qnil) {
arena->pinned_objs = rb_ary_new();
RB_OBJ_WRITE(_arena, &arena->pinned_objs, rb_ary_new());
}
rb_ary_push(arena->pinned_objs, obj);
}
Expand Down

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