swung0x48/MobileGL
1
0
Fork 0
mirror of https://github.com/MobileGL-Dev/MobileGL synced 2026-09-10 05:08:31 +09:00
Code Issues Packages Projects Releases Wiki Activity
Files
712c94674433374c2e2696b8db2e1f9d265ea1eb
MobileGL/MobileGL/MG_Backend/DirectGLES/SlotTables.h
T

578 lines
34 KiB
C++
Raw Blame History

// MobileGL - MobileGL/MG_Backend/DirectGLES/SlotTables.h
// Copyright (c) 2025-2026 MobileGL-Dev
// Licensed under the GNU Lesser General Public License v3.0:
// https://www.gnu.org/licenses/gpl-3.0.txt
// https://www.gnu.org/licenses/lgpl-3.0.txt
// SPDX-License-Identifier: LGPL-3.0-only
// End of Source File Header
#pragma once
#include <Includes.h>
#include <MG_Pipe/MGPipeHandles.h>
#if MOBILEGL_PIPE_PUSH
#include <MG_Impl/Pipe/SlotAllocator.h>
#endif
// Espryt 0b, the first Track H slice: the DENSE, {slot, gen}-keyed twin table that replaces
// StateBackendObjectRegistry's UnorderedMap<StateObject*, Entry>.
//
// What changes, and why each of them is the point:
//
// * The KEY stops being a frontend heap address. It is MGPipeHandle{Slot, Gen}, minted by the
// client's MGPipeSlotAllocator off the frontend object's GetLifetimeId(). A recycled heap
// address cannot reproduce a handle, so the weak_ptr the registry carried per entry purely
// to catch that (its Entry::stateRef, used as an IDENTITY test) stops being an identity
// mechanism, and OwnerEquals / TwinLookupMemo x3 / UnitSamplerLookupMemo's owner compare all
// lose their reason to exist.
// * The lookup stops being a hash probe into an open-addressed map and becomes one bounds
// check plus one array index, so a returned BackendPtr* is NOT invalidated by the next Find
// on the table. That kills the hazard Managers.h documents at length, and with it the
// by-value copy plus second Find that SyncTextureObjectToBackend paid to survive it.
// * Slots are dense per kind, which is what lets the server side (ARCHITECTURE.md 10.1,
// MG_Remote/Server/PipeObjectTables) be an array rather than an object graph.
//
// Death is ANNOUNCED, and that is what lets this table have no garbage collector - the
// deliverable ROADMAP.md:18 spells "GC" in and the one D13 makes a precondition of the switch-
// over. All six re-keyed object classes raise MG_State::GLState::NotifyStateObjectDestroyed()
// from their destructor (BufferBackendOps' shape, one entry point for six kinds), the backend
// consumes it in Managers.cpp, and OnFrontendObjectDestroyed() below drops the twin in EVERY
// table of the kind and returns the slot, at the moment the frontend object's last SharedPtr
// goes. So:
// * there is NO draw-path tick, NO creation tick and NO sweep of any kind on this arm. The
// seven CollectGarbageIfNeeded call sites in DirectGLES.cpp drive the LEGACY registry only;
// * a twin, and the driver storage it owns, is freed when the application lets go of the
// object rather than up to 64 creations or 1024 draw ticks later. That is what
// Managers.h's "dead gigabytes" note asked for.
//
// EVERY HOLDER OF THE KIND, not one. Two live tables of one kind is a real configuration - the
// ScopedDirectGLESTextureBindings fixture keeps a by-value copy of the Texture registry for the
// length of a test, and a context reset does the same in reverse - and the slot allocator
// erases its lifetimeId -> slot mapping on Free, so a notice delivered to one holder and
// resolved again by the next would find nothing to resolve. Every table therefore links itself
// into a per-table-type list at construction and out at destruction, and one notice resolves
// the handle ONCE, drops the twin in each holder BY HANDLE, and frees the slot once, last. No
// holder can be left naming a live entry for a dead object, and there is nothing a sweep could
// still find. (The list is per table TYPE; the kind is the type's template parameter, and each
// of the six kinds has exactly one table type in this backend. Magma's subsystem-4 table mints
// out of its own per-renderer allocator, not MGPipeSlots(), so it is not a holder here.)
//
// The weak_ptr per entry survives for exactly one reason: ForEachLive() hands the callee a
// STRONG reference to the frontend object, which the one direct-iteration site
// (ScopedDetachedTextureFramebufferAttachments) needs. It is never an identity test - that is
// what Gen is for - and it is never read to decide whether an entry is dead: a destructor that
// runs after exit() has begun has its notice dropped by InProcessTeardown(), and that twin is
// then a DELIBERATE leak (the process is exiting, the driver reclaims the object, and a twin
// destructor must not call into a driver that may already be unloaded), not something to be
// collected later.
//
// P3+ DEBT, recorded rather than hidden: this header is under MG_Backend/ and it MINTS
// handles (MGPipeSlots().Acquire below) off a frontend SharedPtr's GetLifetimeId().
// MGPipeHandles.h:13-16 says a handle is minted by the CLIENT and never by the server, and
// under a real split neither the frontend object nor its lifetime id exists on this side of
// the wire. This is monolith glue: the minting and the lifetimeId -> handle resolution both
// belong on the client, and the backend should receive the handle in the verb payload. It is
// NOT part of "Track H done" and check_include_closure.py does not probe MG_Backend headers,
// so nothing catches it automatically.
namespace MobileGL::MG_Backend::DirectGLES {
#if MOBILEGL_PIPE_PUSH
// Declared in Managers.h as well; repeated here because this header is included from it
// before that declaration, and the table below is the arming site on this arm (D13: "the
// arming site moves to the slot table's first insertion").
void EnsureProcessTeardownSentinel();
// What the two knobs add up to. Split out as a PURE function of them so a test can drive
// every combination without needing a process per combination.
enum class EsprytSlotArmVerdict {
Handles, // kMGPipeSubsystemEsprytSlots is set: the {slot, gen} tables run.
Legacy, // the bit is clear and the legacy address-keyed registry is reachable.
NoArm, // the bit is clear AND MOBILEGL_PIPE_LEGACY_MEMOS=0 made the legacy arm
// unreachable, so the operator asked for a configuration with no arm at all.
};
EsprytSlotArmVerdict ClassifyEsprytSlotArm(Bool subsystemBitSet, Bool legacyMemosEnabled);
// This process's verdict, read off MG_Config::Features. Latches nothing and stops nothing.
EsprytSlotArmVerdict CurrentEsprytSlotArmVerdict();
// Says, at backend bring-up, that the knobs leave no arm - and does NOT stop.
//
// The stop cannot live here, and that is the whole point of the split. Backend context
// creation runs inside eglMakeCurrent, and the integration harness pre-flights exactly that
// sequence in a FORKED CHILD (MG_IntegrationTest/Harness/HeadlessGL.cpp): a child that dies
// on a signal is reported as "no usable GPU/display/ICD" and every scenario in the lane is
// SKIPPED - i.e. the lane goes green having run nothing, on the very pair of env vars the
// D14/D18 A/B is driven with, which is what ROADMAP.md:7 forbids. So bring-up only
// DIAGNOSES; the stop is raised by ResolveEsprytSlotTablesArm() at the first twin lookup,
// which happens in the test body where the harness reports it as a failure.
//
// The CALL SITE (InitDisplayAndContext in DirectGLES.cpp) is pinned by
// DirectGLESSlotTable.EglBringUpUnderTheArmlessKnobPairReturnsInsteadOfStopping, which runs
// the real bring-up entry point under the pair in a forked child: edit that site back to
// ResolveEsprytSlotTablesArm() and the case fails naming both knobs.
void DiagnoseEsprytSlotArm();
// Reads the config, logs, installs the death-notice consumer, and STOPS when the operator
// left no arm at all. Cold: called exactly once per process, from the latch below - i.e. at
// the first twin lookup, which is the first moment an arm is actually needed. A process
// that never twins anything needs no arm and is not stopped.
Bool ResolveEsprytSlotTablesArm();
// True when this process runs the {slot, gen} arm. Fixed for the life of the process: the
// two arms hold their twins in different containers, so flipping mid-run would strand them.
//
// INLINE on purpose. Every Find / GetOrCreate / HandleOf / ForEachLive on the twin tables
// consults it, i.e. it is on the per-draw path several times per draw. As an out-of-line
// function in Managers.cpp (no LTO in any shipped configuration) that was a call through
// the PLT per lookup; here the caller sees a guard-variable load and a perfectly-predicted
// branch, and the arm dispatch folds into the caller.
inline Bool EsprytSlotTablesEnabled() {
static const Bool enabled = ResolveEsprytSlotTablesArm();
return enabled;
}
template <typename StateObject, typename BackendObject, MG_Pipe::MGPipeKind kKind>
class BackendSlotTable {
public:
using StatePtr = SharedPtr<StateObject>;
using StateWeakPtr = std::weak_ptr<StateObject>;
using BackendPtr = SharedPtr<BackendObject>;
// The largest slot index this table will grow to for a handle that ARRIVED in a call's
// payload. Slots are dense and allocated per kind, so a million of one kind is already
// far past any application's live object count; the cap is here because the alternative
// is letting a corrupt 32-bit slot decide a vector resize. See GetOrCreate(MGPipeHandle).
static constexpr Uint32 kMaxHandleSlot = 1u << 20;
struct Entry {
BackendPtr backend;
// LIVENESS ONLY, and only for ForEachLive(), which locks it so the callee holds a
// strong ref. Never compared against another object to decide identity - that is
// what Gen is for - never dereferenced for its address, and never read to decide
// whether the slot is dead: death is announced, not discovered.
StateWeakPtr stateRef;
// The generation this entry's twin was built for. An entry whose Gen no longer
// matches the allocator's is a twin of the slot's PREVIOUS owner.
Uint32 Gen = 0;
Bool Live = false;
};
// Every constructor links the table into the per-type holder list and the destructor
// unlinks it, so a by-value copy (the ScopedDirectGLESTextureBindings fixture's saved
// registry) is a holder for exactly as long as it exists. Copy and move carry the
// ENTRIES and the memo; the links are the table's own and are never copied.
BackendSlotTable() { LinkHolder(); }
BackendSlotTable(const BackendSlotTable& other):
m_slots(other.m_slots),
m_nullTwin(other.m_nullTwin),
m_memoLifetimeId(other.m_memoLifetimeId),
m_memoHandle(other.m_memoHandle) {
LinkHolder();
}
BackendSlotTable(BackendSlotTable&& other) noexcept:
m_slots(std::move(other.m_slots)),
m_nullTwin(std::move(other.m_nullTwin)),
m_memoLifetimeId(other.m_memoLifetimeId),
m_memoHandle(other.m_memoHandle) {
other.m_slots.clear();
other.ForgetHandle();
LinkHolder();
}
BackendSlotTable& operator=(const BackendSlotTable& other) {
if (this != &other) {
m_slots = other.m_slots;
m_nullTwin = other.m_nullTwin;
m_memoLifetimeId = other.m_memoLifetimeId;
m_memoHandle = other.m_memoHandle;
}
return *this;
}
BackendSlotTable& operator=(BackendSlotTable&& other) noexcept {
if (this != &other) {
m_slots = std::move(other.m_slots);
m_nullTwin = std::move(other.m_nullTwin);
m_memoLifetimeId = other.m_memoLifetimeId;
m_memoHandle = other.m_memoHandle;
other.m_slots.clear();
other.ForgetHandle();
}
return *this;
}
~BackendSlotTable() { UnlinkHolder(); }
// Resolve-or-create. The handle comes from the client allocator keyed on the frontend
// object's lifetime id, so two calls for the same live object always land on the same
// slot, and a successor object at the same heap address never does.
BackendPtr& GetOrCreate(const StatePtr& stateObj) {
// No assert on null here, unlike the map arm: null is TOLERATED, so a DEBUG build
// must not trap where the release build quietly does the documented thing.
if (stateObj == nullptr) {
// The registry this replaces inserted a null KEY and handed back that entry's
// twin (DirectGLES.cpp's SyncTextureObjectToBackend documents relying on
// exactly that tolerance), so a release build never dereferenced null here.
// Keep the shape exactly, INCLUDING across calls: the map kept its null-keyed
// entry, so a second null call was handed the same twin the first one got.
// Resetting here instead would have destroyed it - an arm difference in the one
// path that documents relying on this. One per-table parking slot, never live,
// never handed a handle, because a null object has no identity and
// therefore cannot have a {slot, gen}.
return m_nullTwin;
}
// D13: the teardown sentinel is armed by the slot table's first insertion. Twin
// creation is the moment a driver-owned id starts needing a guarded destructor;
// this is the cold path, so the once-guard costs nothing per draw. On the legacy
// arm StateBackendObjectRegistry::GetOrCreate arms it itself.
EnsureProcessTeardownSentinel();
const MG_Pipe::MGPipeHandle handle =
MG_Pipe::MGPipeSlots().Acquire(kKind, stateObj->GetLifetimeId());
MOBILEGL_ASSERT(!MG_Pipe::MGPipeHandleIsNull(handle),
"MGPipe slot space of kind %u is exhausted",
static_cast<Uint32>(kKind));
Entry& entry = EntryAt(handle.Slot);
if (entry.Live && entry.Gen != handle.Gen) {
// The slot was reclaimed and handed to a new object: the twin at it describes
// driver ids the new state object never made.
entry.backend.reset();
}
entry.Gen = handle.Gen;
entry.Live = true;
entry.stateRef = stateObj;
// No creation tick and no sweep here. The registry this replaces needed both,
// because nothing told it a texture or a renderbuffer had been DELETED and object
// CHURN rather than draw count is what made that urgent. Every one of the six kinds
// now announces its own death from its destructor, so a dead twin's slot is already
// back before the next creation asks for one.
RememberHandle(stateObj->GetLifetimeId(), handle);
return entry.backend;
}
// P3a: resolve-or-create BY HANDLE, and it is the shape that discharges the debt this
// header records against itself at the top of the file.
//
// The overload above mints - it calls MGPipeSlots().Acquire off a frontend object's
// lifetime id, from inside MG_Backend - which is monolith glue: a handle is minted by
// the CLIENT, and under a real split neither the object nor its lifetime id exists on
// this side. This overload never touches the allocator at all. The handle ARRIVED, in
// the call's payload, already minted by the side that owns minting; all this does is
// index the slot, notice a generation that no longer matches (the slot was recycled,
// so the twin at it describes driver ids the new resource never made) and hand back
// the twin pointer. FindByHandle beside it is the same shape and already existed.
//
// No StatePtr, therefore no Entry::stateRef: the weak pointer is liveness for
// ForEachLive() and a handle-keyed entry has no frontend object to weakly hold. Such
// an entry is therefore invisible to ForEachLive, which is correct - the one direct
// iteration site walks texture twins, and it is not one of these tables.
//
// Death stays ANNOUNCED, as it is on the other overload: for a handle-keyed kind the
// announcement is the family's own destroy call, not the shared death notice, and the
// slot is freed by the CLIENT after that call returns.
//
// UNUSED AT THE CONTRACT COMMIT, deliberately: it is a member of a class template, so
// an uninstantiated one costs nothing anywhere, and the backend package is what gives
// it its first caller.
BackendPtr& GetOrCreate(MG_Pipe::MGPipeHandle handle) {
MOBILEGL_ASSERT(!MG_Pipe::MGPipeHandleIsNull(handle),
"GetOrCreate(handle) named the reserved null handle");
if (MG_Pipe::MGPipeHandleIsNull(handle)) return m_nullTwin;
// A slot index that ARRIVED in a payload indexes a vector this call would RESIZE,
// and nothing between the payload and here bounds it: the applier's blob gates sit
// in front of the vertex-input family, not in front of the resource family, which
// dispatches ops->Create(record.Res, ...) straight through. There is no allocator
// constant to check against on this side - the allocator is the client's - so this
// is a sanity cap and is documented as one: kMaxHandleSlot entries of one kind is
// already orders of magnitude past any real GL object count, while a corrupt 32-bit
// slot asks for a four-billion-entry resize.
if (handle.Slot >= kMaxHandleSlot) {
MOBILEGL_ASSERT(false, "GetOrCreate(handle) named slot %u, past this table's %u bound",
handle.Slot, kMaxHandleSlot);
return m_nullTwin;
}
// Same arming as the minting overload, and for the same reason: twin creation is
// the moment a driver-owned id starts needing a guarded destructor.
EnsureProcessTeardownSentinel();
// THE TWO DIRECTIONS ARE NOT SYMMETRIC HERE, where they are on the minting overload.
// There the handle comes straight out of MGPipeSlots().Acquire and can never be
// BEHIND the entry, so a bare `!=` only ever means "the slot was recycled forward".
// Here the handle arrived in a payload, so `handle.Gen < entry.Gen` is a reachable
// input, and adopting it would destroy the INCUMBENT LIVE twin - a driver buffer id,
// a persistent map, a pooled store, released by a defaulted destructor that issues
// no glDeleteBuffers and no pool enrolment - and then stamp the slot back to the
// dead resource's generation, after which the incumbent's own FindByHandle refuses
// it and it is silently handed a fresh, empty twin. That is a leak AND a resource
// that loses its storage with no diagnostic, i.e. the shape commit d7655247 fixed
// and the thing MGPipeHandle::Gen exists to prevent. So: forward is a recycle and
// resets the twin, BACKWARD is refused - which is the same answer FindByHandle
// below already gives the same input.
Entry& entry = EntryAt(handle.Slot);
if (entry.Live && entry.Gen > handle.Gen) {
MOBILEGL_ASSERT(false,
"GetOrCreate(handle) named generation %u at slot %u, which is BEHIND "
"the live entry's %u - refusing rather than destroying the incumbent",
handle.Gen, handle.Slot, entry.Gen);
return m_nullTwin;
}
if (entry.Live && entry.Gen != handle.Gen) entry.backend.reset();
entry.Gen = handle.Gen;
entry.Live = true;
return entry.backend;
}
// The generation of the LIVE entry at this slot, or 0 when the slot is out of range or
// holds no live entry. It exists so a caller can DIAGNOSE - in a release build, where
// MOBILEGL_ASSERT is inert - the refusal GetOrCreate(handle) above performs silently.
Uint32 LiveGenAt(Uint32 slot) const {
if (slot >= m_slots.size()) return 0;
const Entry& entry = m_slots[slot];
return entry.Live ? entry.Gen : 0;
}
// P3a: the death half of the overload above, for a kind whose announcement is its own
// destroy CALL rather than the shared death notice (D-L). Hands the twin OUT rather
// than destroying it in place, because the caller may still have to decide what
// happens to the driver id it owns - Espryt pools it, deletes it, or parks it on the
// deferred-release list when no context is current on this thread - and every one of
// those outcomes has to be reached with the entry already retired, so a re-entrant
// GetOrCreate from a twin destructor cannot resurrect it.
//
// The slot itself is NOT freed here: it belongs to the kind, and for a handle-keyed
// kind the CLIENT frees it after the destroy call returns (SlotAllocator.h:60 - the
// Gen bump rides the next handout, so a double free cannot skip a generation). An
// entry whose Gen no longer matches is a twin of the slot's previous owner and is
// left alone: the successor's own GetOrCreate resets it.
BackendPtr ReleaseByHandle(MG_Pipe::MGPipeHandle handle) {
if (MG_Pipe::MGPipeHandleIsNull(handle)) return BackendPtr{};
if (m_memoHandle.Slot == handle.Slot) ForgetHandle();
if (handle.Slot >= m_slots.size()) return BackendPtr{};
Entry& entry = m_slots[handle.Slot];
if (!entry.Live || entry.Gen != handle.Gen) return BackendPtr{};
BackendPtr dead = std::move(entry.backend);
entry.backend.reset();
entry.stateRef.reset();
entry.Live = false;
return dead;
}
// Null when no live twin of this object exists. Unlike the registry's Find this NEVER
// mutates the table, so the returned pointer survives any later Find on it; only a
// GetOrCreate that grows the vector can move it, and callers that hold one across a
// possible insertion still copy the BackendPtr out.
BackendPtr* Find(StateObject* stateObj) {
if (stateObj == nullptr) return nullptr;
return FindByHandle(HandleOf(stateObj));
}
const BackendPtr* Find(StateObject* stateObj) const {
return const_cast<BackendSlotTable*>(this)->Find(stateObj);
}
BackendPtr* FindByHandle(MG_Pipe::MGPipeHandle handle) {
if (MG_Pipe::MGPipeHandleIsNull(handle)) return nullptr;
if (handle.Slot >= m_slots.size()) return nullptr;
Entry& entry = m_slots[handle.Slot];
if (!entry.Live || entry.Gen != handle.Gen) return nullptr;
return &entry.backend;
}
// The handle this object's twin is keyed on, or the null handle. This is what a backend
// memo stores instead of a raw pointer, a GL name or a bare lifetime id.
//
// A NULL answer is never memoised. The memo is per table and the allocator is per
// kind, so with two holders of one kind the OTHER table can be the one that acquires;
// a cached "no handle" here would then outlive the twin's creation over there, and
// nothing on this table's own acquire path would ever refresh it. A miss costs the
// allocator probe it always cost; a hit is refreshed the moment anyone acquires.
MG_Pipe::MGPipeHandle HandleOf(const StateObject* stateObj) const {
if (stateObj == nullptr) return MG_Pipe::kMGPipeNullHandle;
const Uint64 lifetimeId = stateObj->GetLifetimeId();
if (lifetimeId == m_memoLifetimeId) return m_memoHandle;
const MG_Pipe::MGPipeHandle handle =
MG_Pipe::MGPipeSlots().FindByLifetimeId(kKind, lifetimeId);
if (!MG_Pipe::MGPipeHandleIsNull(handle)) RememberHandle(lifetimeId, handle);
return handle;
}
// P2 step e2's backend half. The frontend object with this lifetime id has just been
// DESTROYED: resolve its handle ONCE, drop its twin in EVERY table of this type, and
// return the slot to the allocator - in that order, because the allocator forgets the
// lifetime id on Free and a holder told second could no longer resolve it.
//
// The slot is returned whether or not any holder still had a twin at it: the lifetime
// id is dead and MG_State never hands one out twice, so nothing can acquire it again,
// and a slot minted for it that no table holds (a table reset with `= {}` drops its
// entries without freeing) would otherwise stay allocated for the life of the process.
//
// STATIC, and deliberately so: a notice is about an object, not about a table, and
// "which table holds it" is exactly the question that produced the two-holder leak.
// Returns whether the object had a slot of this kind, i.e. whether anything was freed;
// a second call for the same id answers false because the allocator no longer maps it.
static Bool OnFrontendObjectDestroyed(Uint64 lifetimeId) {
const MG_Pipe::MGPipeHandle handle =
MG_Pipe::MGPipeSlots().FindByLifetimeId(kKind, lifetimeId);
if (MG_Pipe::MGPipeHandleIsNull(handle)) return false;
for (BackendSlotTable* holder = s_firstHolder; holder != nullptr;) {
// The successor is read BEFORE the release: ReleaseTwinAt runs the twin's
// destructor, which is a driver call, and nothing that outlives it may be a
// reference into this holder.
BackendSlotTable* const next = holder->m_nextHolder;
holder->ReleaseTwinAt(handle);
holder = next;
}
MG_Pipe::MGPipeSlots().Free(kKind, handle);
return true;
}
// How many tables of this type exist right now. For the tests that pin the holder
// list; nothing on a shipping path asks.
static Uint32 HolderCount() {
Uint32 count = 0;
for (const BackendSlotTable* holder = s_firstHolder; holder != nullptr;
holder = holder->m_nextHolder) {
++count;
}
return count;
}
// fn(const StatePtr& state, const BackendPtr& twin) over every live, still-owned entry.
// Replaces the registry's begin()/end(), whose iterator exposed the raw frontend
// address as the map key - the one place the backend read an identity it must not have.
// The state object is handed over as a STRONG reference, so the callee cannot be handed
// a dangling key the way the old iteration could.
template <typename Fn>
void ForEachLive(Fn&& fn) const {
// Index loop and a COPIED twin, not a range-for over references: fn is arbitrary
// backend code, and a nested GetOrCreate on this table would resize m_slots and
// invalidate both the iterator and any reference into the vector that outlives the
// call. The one caller today happens not to insert; that is not a property the
// walk should depend on.
for (SizeT slot = 0; slot < m_slots.size(); ++slot) {
const Entry& entry = m_slots[slot];
if (!entry.Live || !entry.backend) continue;
const StatePtr state = entry.stateRef.lock();
if (!state) continue;
const BackendPtr twin = entry.backend;
fn(state, twin);
}
}
Uint32 LiveCount() const {
Uint32 count = 0;
for (const Entry& entry : m_slots) {
if (entry.Live) ++count;
}
return count;
}
private:
// Drop the twin at `handle` if THIS table holds it. Frees nothing: the slot belongs to
// the kind, not to the table, and OnFrontendObjectDestroyed returns it once, after
// every holder has let go.
Bool ReleaseTwinAt(MG_Pipe::MGPipeHandle handle) {
// Forget the memo whenever it names this slot, even if this table has no entry
// there: a memo can be a handle learned from the allocator for an object another
// holder twinned, and it must not survive the slot's next handout.
if (m_memoHandle.Slot == handle.Slot) ForgetHandle();
if (handle.Slot >= m_slots.size()) return false;
// The twin's destructor is a driver call and could, in principle, re-enter
// GetOrCreate on this table and resize m_slots. So NOTHING that outlives the
// destructor may be a reference into m_slots: the twin is moved out into a local,
// the entry is finished with, and only then is the local released.
BackendPtr dead;
{
Entry& entry = m_slots[handle.Slot];
if (!entry.Live || entry.Gen != handle.Gen) return false;
dead = std::move(entry.backend);
entry.backend.reset();
entry.stateRef.reset();
entry.Live = false;
}
dead.reset();
return true;
}
// Grows the table to hold `slot`. Every caller bounds `slot` first - the minting
// overload because the allocator produced it, the handle overload against
// kMaxHandleSlot - because this is the one place a client-supplied number decides an
// allocation size.
Entry& EntryAt(Uint32 slot) {
if (slot >= m_slots.size()) m_slots.resize(static_cast<SizeT>(slot) + 1);
return m_slots[slot];
}
void RememberHandle(Uint64 lifetimeId, MG_Pipe::MGPipeHandle handle) const {
m_memoLifetimeId = lifetimeId;
m_memoHandle = handle;
}
void ForgetHandle() const {
m_memoLifetimeId = 0;
m_memoHandle = MG_Pipe::kMGPipeNullHandle;
}
// The holder list: intrusive and doubly linked, so registering and unregistering are
// two pointer writes with no allocation, and its head is a constant-initialised
// static - which is what lets the process-lifetime registry globals in Managers.cpp
// link themselves in from their own constructors with no initialisation-order
// question to answer. Single-threaded, like every table it links (the tables live and
// die on the context thread, as the notice they answer does).
void LinkHolder() {
m_prevHolder = nullptr;
m_nextHolder = s_firstHolder;
if (s_firstHolder != nullptr) s_firstHolder->m_prevHolder = this;
s_firstHolder = this;
}
void UnlinkHolder() {
if (m_prevHolder != nullptr) {
m_prevHolder->m_nextHolder = m_nextHolder;
} else {
s_firstHolder = m_nextHolder;
}
if (m_nextHolder != nullptr) m_nextHolder->m_prevHolder = m_prevHolder;
m_prevHolder = nullptr;
m_nextHolder = nullptr;
}
static inline BackendSlotTable* s_firstHolder = nullptr;
BackendSlotTable* m_prevHolder = nullptr;
BackendSlotTable* m_nextHolder = nullptr;
// Indexed by MGPipeHandle::Slot; [0] is the reserved slot and is never live.
Vector<Entry> m_slots;
// Handed back by GetOrCreate for a null state object. Never live, never handed a handle.
BackendPtr m_nullTwin;
// ONE-entry resolution memo, lifetimeId -> handle. It exists because without it every
// resolution goes through the allocator's ByLifetimeId hash, which the deleted
// TwinLookupMemos existed to avoid and which D13 promises to replace with "direct slot
// indexing".
//
// It is one entry and therefore only helps a caller that asks for the SAME object twice
// running - ResolveVaoTwin and SyncCurrentProgram do, once per draw each. Two callers
// it does NOT help, recorded rather than claimed away: BindCurrentFBO resolves BOTH
// targets in a frame, and ResolveUnitSamplerBackend asks for a different sampler per
// texture unit, so both thrash a single-entry memo and pay the probe P1 did not (P1 had
// a per-unit memo and a direct-mapped 6-slot array there). Making the memo per-unit /
// per-target is the fix, and G11 - the device-side gate that would price it - is owed.
//
// It cannot serve a stale answer, by three independent arguments:
// * the key is a lifetime id, which MG_State never hands out twice, so a recycled
// heap address cannot hit this memo the way it could hit an address-keyed one;
// * a null answer is never stored, so another holder's acquire cannot be hidden by
// a "no handle" this table remembered earlier; and
// * even a hit for a slot that has since been freed and re-handed is caught, because
// the caller resolves the handle through FindByHandle, which compares Gen.
// Cleared anyway when a death notice names the memoised slot. 0 is never a live
// lifetime id (MG_State's counters start at 1), so a zeroed memo is a guaranteed miss.
mutable Uint64 m_memoLifetimeId = 0;
mutable MG_Pipe::MGPipeHandle m_memoHandle = MG_Pipe::kMGPipeNullHandle;
};
#endif // MOBILEGL_PIPE_PUSH
} // namespace MobileGL::MG_Backend::DirectGLES
Reference in New Issue View Git Blame Copy Permalink