swung0x48/MobileGL
1
0
Fork 0
mirror of https://github.com/MobileGL-Dev/MobileGL synced 2026-11-07 01:53:24 +09:00
Code Issues Packages Projects Releases Wiki Activity
Files
b46da7002c36170f6a049f7d30a0ba34bc5cbbd0
MobileGL/MobileGL/MG_Remote/Client/ClientSession.cpp
T
swung0x48 b46da7002c [MG_Remote] (P6/dl): a dying session names itself to the peer 
Step three of CONTRACT-P6 5.2, the funnel's whole point: instead of the peer
reading a bare EOF and guessing, the session publishes a SessionFault frame
that names the family before it aborts.

THE WIRE CHANGE IS D2's, exactly: `table Fatal` appends `family: string`,
append-only, so an older peer still reads `code` and `message`. `code` stays
the coarse seven-value projection; `family` carries the full word.

SessionFail publishes it before the abort, on whichever session's control
plane is active - the client has a ClientSession, the server a ServerSession,
so under spawn the frame reaches the far side whichever role is dying. Under
inproc both exist and it goes to an in-process transport the aborting process
will never read, which is harmless and cheaper than a special case that would
then be the untested one. Best-effort by nature: this thread is about to die,
so a send that blocks or fails changes nothing.

seq/op from the prose are NOT threaded through the 90 sites: the message
already names the op where it matters, so the frame carries what it can name
honestly (code, family, message) rather than a field that is always zero.

The client recognizes it: RunRemoteSurfaceControlFrame's reply loop, which
already demuxes CapsSnapshot from SurfaceReply, gains a Fatal arm that logs the
family and detail, latches device-lost from it, and returns transport-closed.
A server that DETECTS a fatal condition and aborts itself now tells the client
why; a kill -9 still bypasses abort entirely and is caught by dl's hangup
witness instead - the two cover the two ways a server can die.

The census learns SessionFail: a SessionFail call, like a WireLogFatal call,
must carry a Fatal{ word in its string, so the enum and the string cannot
disagree. FatalFunnel.{h,cpp} join the funnel exemption. Baseline is 4 aborts.

FatalFamilyTest gains the wire round-trip: every family's frame carries its
word and its projected code across encode/verify/decode.

G1 re-measured after the schema change: 0 symbol diff, .text unchanged at
0xa52203. Unit 2359 (one pre-existing environmental failure), integration-split
186/186, integration-spawn 102/102, retrace 6/6, census 0 unmarked.
2026-09-21 21:51:50 -04:00

2074 lines
123 KiB
C++
Raw Blame History

// MobileGL - MobileGL/MG_Remote/Client/ClientSession.cpp
// 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
// P5: construction, the handshake and lifetime are package s1's; the verb barrier and the
// reply read that sits inside it are package c1's (EmitAndWait below is still c0's stub).
#include "ClientSession.h"
#include <MG_Remote/FatalFunnel.h>
#include "../CapsCodec.h"
#include "../Protocol/generated/protocol_generated.h"
#include "../Server/ServerLoop.h"
#include "../Server/ServerSession.h"
#include "../Protocol/SurfaceOpCodec.h"
#include "../Transport/FdPassing.h"
#include "../Transport/InProcessTransport.h"
#include "WireTables.h"
#include <MGGitHash.h>
#include <MG_Backend/MGPipe/PipeInputs.h>
#include <MG_Impl/GLImpl/Framebuffer/GL_Framebuffer.h>
#include <MG_Impl/Pipe/ResourceTracker.h>
#include <MG_Pipe/MGPipeCallbacks.h>
#include <MG_State/GLState/Core.h>
#include <MG_State/GLState/ErrorState/ErrorInfo.h>
#include <MG_State/GLState/TextureState/TextureObject2D.h>
#include <MG_Util/Debug/Log.h>
#include <atomic>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <vector>
// CONTRACT-P6 4.3: the handshake now carries real process ids.
#if defined(_WIN32)
#include <process.h>
#else
#include <unistd.h>
#endif
namespace MobileGL::MG_Remote::Client {
namespace {
// CONTRACT-P6 4.3. Hello::pid was hard-coded 0 and Welcome::serverPid ECHOED it, so both
// were always 0 and neither named anything. Under spawn the pair is the cheapest arm
// proof there is: two different values mean two processes, and a same-process session
// cannot produce them.
std::uint32_t SelfProcessId() {
#if defined(_WIN32)
return static_cast<std::uint32_t>(::_getpid());
#else
return static_cast<std::uint32_t>(::getpid());
#endif
}
} // namespace
#define MGP5_C0_STUB(what) \
SessionFail(MGFatalFamily::UnimplementedClientSession, \
"MGPipe: Fatal{UnimplementedClientSession, \"%s\"} - P5 packages s1/c1 have not " \
"landed this yet; c0 shipped the signature only", \
what)
namespace {
ClientSession* g_active = nullptr;
// The same bounded handshake deadline the server uses. Bounded, not kWaitForever: a
// bring-up that never answers has to be a red lane rather than a wedged CI job.
constexpr Uint32 kHandshakeTimeoutMs = 5000;
// cp (CONTRACT-P6 D5b): bounded, and its expiry is NOT fatal. A peer that
// is gone is a different fact from a peer that is slow, and only the
// doorbell death latch may say which.
constexpr Uint32 kRemoteControlTimeoutMs = 5000;
// The server has to create a backend before it binds, and a cold
// software rasteriser is not fast. Bounded, and a NAMED refusal at the end.
constexpr Uint32 kSpawnConnectTimeoutMs = 20000;
// Teardown's drain. Also bounded, and for the same reason - table 3's order is
// "publish and wait for the server to drain and acknowledge", and a wait with no
// deadline there turns a lost record into a hung process exit.
constexpr Uint32 kDrainTimeoutMs = 5000;
MobileGLResult ReceiveEnvelope(Transport::ITransport& transport, std::vector<Uint8>& out,
Uint32 timeoutMs) {
Uint64 size = 0;
MobileGLMutableByteSpan empty{nullptr, 0};
const MobileGLResult probe = transport.ReceiveFrame(empty, &size, timeoutMs);
if (probe != MOBILEGL_ERR_BUFFER_TOO_SMALL) {
return probe == MOBILEGL_OK ? MOBILEGL_ERR_PROTOCOL_MISMATCH : probe;
}
out.resize(static_cast<SizeT>(size));
MobileGLMutableByteSpan span{out.data(), out.size()};
return transport.ReceiveFrame(span, &size, 0);
}
const ::MobileGL::Wire::CtrlEnvelope* ParseEnvelope(const std::vector<Uint8>& bytes) {
::flatbuffers::Verifier verifier(bytes.data(), bytes.size());
if (!::MobileGL::Wire::VerifyCtrlEnvelopeBuffer(verifier)) {
return nullptr;
}
if (!::MobileGL::Wire::CtrlEnvelopeBufferHasIdentifier(bytes.data())) {
return nullptr;
}
return ::MobileGL::Wire::GetCtrlEnvelope(bytes.data());
}
// CONTRACT-P6 4.3: THE DECLARED PROTOCOL VERSION, WHICH THIS SIDE NEVER READ.
//
// Hello has carried abiMajor/abiMinor since P5 and the SERVER checks them, but the
// client only ever compared the fingerprint - so the asymmetry was silent in the one
// direction that matters for spawn, where the peer is a SEPARATE IMAGE the operator
// chose with MOBILEGL_IPC_SERVER_PATH.
//
// The fingerprint mixes AbiVersion and would catch a mismatch anyway, but it catches it
// as "struct shapes" - which sends the reader looking for a layout change that is not
// there. Checking the version FIRST turns the same failure into the sentence that
// explains it. Both handshake sites call this; there are two, and only one of them used
// to be reachable, which is how the gap survived review.
[[noreturn]] void FatalProtocolVersionMismatch(unsigned theirMajor, unsigned theirMinor,
const char* theirStamp) {
SessionFail(MGFatalFamily::AbiMismatch, "MGPipe: Fatal{AbiMismatch, \"protocol version\"} ours=%u.%u theirs=%u.%u "
"ourBuild=%s theirBuild=%s - the peer speaks a different MGPipe protocol. "
"Under spawn this is most often a stale MOBILEGL_IPC_SERVER_PATH pointing at "
"a libMobileGLServer.so built from another tree.",
static_cast<unsigned>(MOBILEGL_PROTOCOL_ABI_MAJOR),
static_cast<unsigned>(MOBILEGL_PROTOCOL_ABI_MINOR), theirMajor, theirMinor,
GIT_COMMIT_HASH_SHORT, theirStamp == nullptr ? "?" : theirStamp);
}
[[noreturn]] void FatalAbiMismatch(const char* what, Uint64 ours, Uint64 theirs,
const char* theirStamp) {
SessionFail(MGFatalFamily::AbiMismatch, "MGPipe: Fatal{AbiMismatch, \"%s\"} ours=%llu theirs=%llu ourBuild=%s "
"theirBuild=%s - never a downgrade: the caps block's size is ABI-dependent "
"and every field past the first difference would be read at the wrong offset",
what, static_cast<unsigned long long>(ours),
static_cast<unsigned long long>(theirs), GIT_COMMIT_HASH_SHORT,
theirStamp == nullptr ? "?" : theirStamp);
}
// Guarded the same way ServerSession's helpers are: MG_Config::Ipc only exists
// behind MOBILEGL_BUILD_DISAGGREGATED (Config.h), and this file is only compiled
// there today - but the guard is what keeps that true if the source list ever
// changes, and an unguarded read would be a compile error nobody could read.
Uint32 SpinUsFromConfig() {
#if MOBILEGL_BUILD_DISAGGREGATED
return MG_Config::Ipc.SpinUs;
#else
return Transport::kDefaultSpinUs;
#endif
}
Bool VerbBarrierFromConfig() {
#if MOBILEGL_BUILD_DISAGGREGATED
return MG_Config::Ipc.VerbBarrier != 0;
#else
return true;
#endif
}
// ---- c1: the barrier's two flags ------------------------------------------------
//
// thread_local for the client's own "am I waiting", a shared atomic for "is the apply
// thread inside the applier" - see ClientSession::InBarrierWait's note.
thread_local Bool g_inBarrierWait = false;
std::atomic<Bool> g_applyThreadInsideApplier{false};
// A split client cannot observe a server's process-local diagnostic. The
// role-local value remains useful to the applier itself; ordering between
// roles is carried by the ring watermarks, not by this instrumentation.
thread_local Bool g_roleInsideApplier = false;
struct BarrierWaitScope {
BarrierWaitScope() { g_inBarrierWait = true; }
~BarrierWaitScope() { g_inBarrierWait = false; }
BarrierWaitScope(const BarrierWaitScope&) = delete;
BarrierWaitScope& operator=(const BarrierWaitScope&) = delete;
};
// A DEADLOCK DETECTOR, NOT A PERFORMANCE GATE. The barrier exists so that a record the
// applier never retires is reported instead of hanging: a lost record never completes at
// all, while a slow apply completes late. The bound only has to sit far above the slowest
// legitimate apply.
//
// lavapipe/llvmpipe have legitimate apply-thread stalls that reach the tens of seconds:
// texture-handle registration (vkCreateImageView -> lvp_CreateImageView ->
// llvmpipe_register_texture) blocks the apply thread on a JIT/futex path, measured at
// 29.3-39.7 s in a single stall, ~44.6 s cumulatively over one inproc retrace run. A 30 s
// bound therefore red-lanes those runs intermittently while the same stall on a monolith
// run is simply slow - the monolith has no equivalent cap on this path. 120 s is >3x the
// largest observed stall and keeps the watchdog's job: a record that is truly lost still
// terminates the run, and the Fatal names the seq.
constexpr Uint32 kBarrierTimeoutMs = 120000;
Uint64 AppliedWaitBudgetMs(MG_Pipe::MGPWireOp op, const void* payload) {
if (op != MG_Pipe::MGPWireOp::FenceWait) return kBarrierTimeoutMs;
const Uint64 timeoutNs = static_cast<const MG_Pipe::MGPFenceWait*>(payload)->TimeoutNs;
// ClientWaitSync may legitimately block longer than the ordinary verb barrier.
// Round up without overflowing UINT64_MAX, then allow the usual transport grace.
// FenceWaitServer queues a GPU wait; its GL_TIMEOUT_IGNORED is not a CPU budget.
return timeoutNs / 1000000 + (timeoutNs % 1000000 != 0) + kBarrierTimeoutMs;
}
// Defined below; declared here because the applied wait has to be able to drain
// SEG_EVENT while it is parked (P5e §2.6).
Uint32 DrainEventRing(Transport::EventRingConsumer& events);
Transport::SessionWait WaitForAppliedBudget(Transport::SessionProducer& producer,
Transport::EventRingConsumer& events,
Uint64 seq, Uint64 remainingMs) {
// The transport takes Uint32 milliseconds with UINT32_MAX meaning forever.
// Keep even the largest GL timeout finite, using bounded chunks and preserving
// the doorbell's immediate shutdown result. Avoid a giant chrono deadline too.
constexpr Uint32 kMaxFiniteWaitMs = Transport::kWaitForever - 1;
for (;;) {
const Uint32 chunkMs = remainingMs > kMaxFiniteWaitMs
? kMaxFiniteWaitMs : static_cast<Uint32>(remainingMs);
// P5e (ra, CONTRACT-P5E §2.6): THE PARK BREAKS ON TWO THINGS. A server that
// ran out of SEG_EVENT stops producing and therefore stops applying, so a
// waiter that could only be woken by appliedSeq would wait for a watermark
// nothing is going to move - and it is holding the only drain there is. The
// second exit is that case: drain, clear the latch, ring the server, park
// again. `remainingMs` is deliberately NOT charged for it; a wake that did
// the queue's work is not the caller's budget being spent.
const auto wait = producer.WaitForAppliedOrEventBacklog(seq, chunkMs);
if (wait == Transport::SessionWait::Reached) {
Transport::RingControl* control = producer.Control();
if (control == nullptr ||
Transport::Watermark::Reached(control->Progress.appliedSeq, seq)) {
return wait;
}
DrainEventRing(events);
continue;
}
if (wait != Transport::SessionWait::TimedOut || remainingMs <= chunkMs) return wait;
remainingMs -= chunkMs;
}
}
// How many queued control frames one pump will drain. A backlog deeper than this is a
// finding, not a steady state.
constexpr Uint32 kMaxControlFramesPerPump = 16;
const char* TransportModeName(MG_Config::TransportMode mode) {
switch (mode) {
case MG_Config::TransportMode::Monolith: return "monolith";
case MG_Config::TransportMode::InProcess: return "inproc";
case MG_Config::TransportMode::Spawn: return "spawn";
case MG_Config::TransportMode::UnixSocket: return "unix:";
case MG_Config::TransportMode::NamedPipe: return "pipe:";
}
return "?";
}
// ---- c1: the reverse channel's reading end ---------------------------------------
//
// R-12's three: OnBufferWriteback (#3), OnGpuWritten (#2), OnSurfaceChanged (#7).
// Drained BY THE GL THREAD BETWEEN VERBS, which under the barrier means immediately
// after appliedSeq reaches this record - the one moment at which the apply thread is
// known not to be inside the applier.
//
// THE BYTES LIVE IN THE RING ITSELF, so Drained() is called only after every payload
// pointer popped here has been consumed: retiring earlier is R-11's violation one level
// down (EventRing.h:168-171 says so in as many words).
//
// THE CONSUMERS ARE CALLED BY NAME, NEVER THROUGH gMGPipeCallbacks (CONTRACT-P5C
// §4.1): with an active transport the global table's reverse entries are the SERVER
// session's producer callbacks, so routing the drain through it would call the
// producer back from the GL thread - the layer-2 violation the contract names.
//
// THE SURFACE-CHANGED CONSUMER IS WHERE R3's OWNERSHIP ALWAYS WAS: the backend
// posts the MGPSurfaceInfo, and the allocate/format writes against
// pDefaultFramebufferInfo happen HERE, on the GL thread, against client memory.
void ApplySurfaceChangedToClient(const MG_Pipe::MGPSurfaceInfo& info) {
auto& defaultFBOInfo = MG_Impl::GLImpl::FramebufferImpl::pDefaultFramebufferInfo;
if (!defaultFBOInfo) return;
const auto format = static_cast<TextureInternalFormat>(info.InternalFormat);
auto* colorTex =
static_cast<MG_State::GLState::TextureObject2D*>(defaultFBOInfo->colorAttachment.get());
auto* depthTex =
static_cast<MG_State::GLState::TextureObject2D*>(defaultFBOInfo->depthAttachment.get());
auto* stencilTex =
static_cast<MG_State::GLState::TextureObject2D*>(defaultFBOInfo->stencilAttachment.get());
if (info.Width != 0 && info.Height != 0) {
// The SWAPCHAIN's publication shape: an extent-carrying event. Reproduces
// SwapchainObject's monolith writes statement for statement - colour storage
// at the extent, depth/stencil format then storage - because
// FramebufferObject::CheckCompleteness requires every attachment to agree.
const Int extentWidth = static_cast<Int>(info.Width);
const Int extentHeight = static_cast<Int>(info.Height);
const SizeT attachmentByteSize =
static_cast<SizeT>(info.Width) * static_cast<SizeT>(info.Height) * 4;
if (colorTex != nullptr) {
colorTex->AllocateStorage(TextureUploadTarget::Texture2D, 0,
{{extentWidth, extentHeight, 1}, attachmentByteSize});
}
if (depthTex != nullptr) {
depthTex->SetInternalFormat(format);
depthTex->AllocateStorage(TextureUploadTarget::Texture2D, 0,
{{extentWidth, extentHeight, 1}, attachmentByteSize});
}
if (stencilTex != nullptr) {
stencilTex->SetInternalFormat(format);
stencilTex->AllocateStorage(TextureUploadTarget::Texture2D, 0,
{{extentWidth, extentHeight, 1}, attachmentByteSize});
}
} else {
// The DirectGLES publication shape: FORMAT ONLY, Width/Height == 0. The
// placeholder's 512x512 extent is deliberately left alone - all three
// attachments share it, and resizing depth/stencil without colour would
// report the default framebuffer incomplete.
if (depthTex != nullptr) depthTex->SetInternalFormat(format);
if (stencilTex != nullptr) stencilTex->SetInternalFormat(format);
}
}
Uint32 DrainEventRing(Transport::EventRingConsumer& events) {
if (!events.Valid()) return 0;
Uint32 delivered = 0;
Transport::RingRecordView view{};
Bool corrupt = false;
while (events.Pop(view, &corrupt)) {
if (corrupt) {
SessionFail(MGFatalFamily::ProtocolCorruption, "MGPipe: Fatal{ProtocolCorruption, \"event-ring\"} - the reverse "
"channel's record stream is corrupt");
}
switch (view.kind) {
case Transport::kEventBufferWriteback: {
if (view.payloadSize < sizeof(Transport::EventBufferWritebackHead)) break;
const auto* head =
static_cast<const Transport::EventBufferWritebackHead*>(view.payload);
const void* bytes = static_cast<const Uint8*>(view.payload) + sizeof(*head);
if (view.payloadSize - sizeof(*head) < head->Size) {
SessionFail(MGFatalFamily::ProtocolCorruption, "MGPipe: Fatal{ProtocolCorruption, \"buffer-writeback\"} - the "
"head declares %llu inline bytes and the record carries %llu",
static_cast<unsigned long long>(head->Size),
static_cast<unsigned long long>(view.payloadSize - sizeof(*head)));
}
// The blobref names SEG_EVENT and the IN-SEGMENT offset of those inline
// bytes - never a host address (R-2's rule B), which is the whole reason
// EventRingConsumer exposes OffsetInSegment at all. The consumer's
// kSegEvent arm resolves it through this session's own SegmentTable.
MG_Pipe::MGPBlobRef blob{};
blob.Seg = Wire::kSegEvent;
blob.Offset = events.OffsetInSegment(bytes);
blob.Size = head->Size;
MG_Pipe::MGPipeClientOnBufferWriteback(
MG_Pipe::MGPipeHandle{head->Resource.Slot, head->Resource.Gen},
head->Offset, blob);
++delivered;
break;
}
case Transport::kEventGpuWritten: {
if (view.payloadSize < sizeof(Transport::EventGpuWrittenHead)) break;
const auto* head =
static_cast<const Transport::EventGpuWrittenHead*>(view.payload);
const Uint64 tail = view.payloadSize - sizeof(*head);
if (tail / sizeof(Transport::EventRange) < head->RangeCount) {
SessionFail(MGFatalFamily::ProtocolCorruption, "MGPipe: Fatal{ProtocolCorruption, \"gpu-written\"} - RangeCount "
"%u does not fit the record's %llu tail bytes",
static_cast<unsigned>(head->RangeCount),
static_cast<unsigned long long>(tail));
}
// EventRange and MGPRange are the same two Uint64s (EventRing.h:61-66
// asserts it), so the tail is handed over as-is rather than copied into
// a second array a later reader could get out of step with.
const auto* ranges = reinterpret_cast<const MG_Pipe::MGPRange*>(
static_cast<const Uint8*>(view.payload) + sizeof(*head));
MG_Pipe::MGPipeClientOnGpuWritten(
MG_Pipe::MGPipeHandle{head->Resource.Slot, head->Resource.Gen},
static_cast<Uint>(head->RangeCount), ranges);
++delivered;
break;
}
case Transport::kEventSurfaceChanged: {
if (view.payloadSize < sizeof(Transport::EventSurfaceChangedHead)) break;
const auto* head =
static_cast<const Transport::EventSurfaceChangedHead*>(view.payload);
MG_Pipe::MGPSurfaceInfo info{};
info.Width = head->Width;
info.Height = head->Height;
info.InternalFormat = head->InternalFormat;
info.Samples = head->Samples;
info.Layers = head->Layers;
info.IsDefault = head->IsDefault;
ApplySurfaceChangedToClient(info);
++delivered;
break;
}
case Transport::kEventGlError: {
if (view.payloadSize < sizeof(Transport::EventGlErrorHead)) break;
const auto* head =
static_cast<const Transport::EventGlErrorHead*>(view.payload);
const char* message =
reinterpret_cast<const char*>(static_cast<const Uint8*>(view.payload) +
sizeof(*head));
const Uint64 tail = view.payloadSize - sizeof(*head);
// MessageBytes == 0 is the corrupt shape, never "no message": the NUL
// travels (CONTRACT-P5C §1, rule A's twin), so a legal record carries at
// least one byte and that byte terminates the string.
if (head->MessageBytes == 0 || tail < head->MessageBytes ||
message[head->MessageBytes - 1] != '\0') {
SessionFail(MGFatalFamily::ProtocolCorruption, "MGPipe: Fatal{ProtocolCorruption, \"kEventGlError\"} - "
"MessageBytes %u against a %llu-byte tail, or the terminating "
"NUL is missing",
static_cast<unsigned>(head->MessageBytes),
static_cast<unsigned long long>(tail));
}
// The error queue is CLIENT state, written here on the GL thread. The
// observation point is the next drain after the post - P9 owns the
// ordering (CONTRACT-P5C §4.2).
if (MG_State::pGLContext != nullptr) {
MG_State::pGLContext->RecordError(
static_cast<ErrorCode>(head->Code),
MakeUnique<GenericErrorInfo>(
String(message, static_cast<SizeT>(head->MessageBytes - 1))));
} else {
MGLOG_E_ONCE("MG_Remote client: a kEventGlError (code %u) arrived with "
"no live context and is dropped",
static_cast<unsigned>(head->Code));
}
++delivered;
break;
}
default:
MGLOG_W("MG_Remote client: reverse-channel record kind %u is not consumed in "
"P5c (four of the ten callbacks are armed; the rest are P9's)",
static_cast<unsigned>(view.kind));
break;
}
}
// AND ONLY NOW. Every payload pointer above has been consumed.
events.Drained();
return delivered;
}
// ---- c1: the CapsSnapshot -> CapsMirror adoption, in ONE place -------------------
//
// Every field of the snapshot has exactly one reader, and a field that fails to decode
// is a REFUSAL rather than a partial adopt: CompileEnv.cpp:123 copies the whole
// DynamicBackendParameters struct into the compile env, so a mirror that adopted three
// of four members would put the fourth's default into a shader fingerprint.
Bool AdoptCapsSnapshot(const ::MobileGL::Wire::CapsSnapshot* snapshot) {
if (snapshot == nullptr) return false;
MG_Pipe::MGPCaps caps{};
const auto* dynamicBytes = snapshot->dynamicParameters();
if (dynamicBytes == nullptr || dynamicBytes->size() != sizeof(caps.Dynamic)) {
// The Hello/Welcome fingerprint already asserted both peers agree on
// sizeof(DynamicBackendParameters), so a disagreement HERE is a corrupt frame
// rather than an ABI skew - which is why it is a refusal and not FatalAbiMismatch.
MGLOG_E("MG_Remote client: CapsSnapshot carries %llu dynamic bytes, this build's "
"struct is %llu - the snapshot is refused whole",
static_cast<unsigned long long>(dynamicBytes == nullptr ? 0
: dynamicBytes->size()),
static_cast<unsigned long long>(sizeof(caps.Dynamic)));
return false;
}
std::memcpy(&caps.Dynamic, dynamicBytes->data(), sizeof(caps.Dynamic));
caps.CallMask = snapshot->callMask();
RendererInfo renderer{};
const auto* rendererBytes = snapshot->rendererInfo();
if (rendererBytes == nullptr ||
!DecodeRendererInfo(rendererBytes->data(), rendererBytes->size(), renderer)) {
MGLOG_E("MG_Remote client: CapsSnapshot's rendererInfo blob did not decode");
return false;
}
MG_Backend::FormatCapabilityCache formats{};
const auto* formatBytes = snapshot->formatCaps();
if (formatBytes == nullptr ||
!DecodeFormatCapabilities(formatBytes->data(), formatBytes->size(), formats)) {
MGLOG_E("MG_Remote client: CapsSnapshot's formatCaps blob did not decode");
return false;
}
const String apiVersion =
snapshot->apiVersion() == nullptr ? String{} : String{snapshot->apiVersion()->c_str()};
// THE SERVER'S BACKEND TYPE, NEVER A NEW "Remote" ENUMERATOR and never guessed from
// the renderer string: GL_Framebuffer.cpp:47, GL_Texture.cpp:6536 and
// CompileEnv.cpp:122 SWITCH on it, and a value they do not know takes a wrong arm
// rather than failing.
const Uint32 rawBackend = snapshot->backendType();
if (rawBackend >= static_cast<Uint32>(BackendType::BackendTypeCount)) {
MGLOG_E("MG_Remote client: CapsSnapshot names backend type %u, which this build "
"has no enumerator for - the snapshot is refused rather than folded onto "
"Unknown, which three frontend switches would silently mis-branch on",
static_cast<unsigned>(rawBackend));
return false;
}
CapsMirrorInstance().Adopt(caps, formats, renderer, apiVersion,
static_cast<BackendType>(rawBackend));
return true;
}
} // namespace
// Null, not a Fatal: MG_Backend::Init() asks whether a session exists before it decides to
// install the remote backend object, and that question has a legitimate "no" - it is the
// monolith answer. Every call that PRESUMES a session aborts instead.
ClientSession* ClientSession::Active() { return g_active; }
Bool ClientSession::DeviceLost() {
const ClientSession* session = Active();
return session != nullptr && session->m_deviceLost.load(std::memory_order_acquire);
}
void ClientSession::LatchDeviceLost(const char* why) {
// exchange, so the log line is written EXACTLY once however many waits notice the same
// hangup at the same moment - and there will be several: the barrier, the control wait
// and the event pump can all be in flight when the server goes.
if (m_deviceLost.exchange(true, std::memory_order_acq_rel)) {
return;
}
MGLOG_E("MGPipe: DEVICE LOST - %s. The server process is gone; every verb from here is "
"DECLINED and glGetGraphicsResetStatus reports GL_UNKNOWN_CONTEXT_RESET. This is "
"latched from the peer's HANGUP and not from any deadline (CONTRACT-P6 5.4): a "
"server one frame behind is P5e's intended steady state and must never read as a "
"dead one. There is no recovery - MOBILEGL_IPC_RESPAWN is the stage that would "
"add one and it is refused by name until then.",
why == nullptr ? "the peer hung up" : why);
}
ClientSession& ClientSessionInstance() {
// Leak at exit, deliberately and per ID-8, exactly as ServerSessionInstance does.
static ClientSession* instance = new ClientSession{};
return *instance;
}
ClientSession::~ClientSession() {
if (m_started) {
Stop();
}
}
Bool ClientSession::Started() const { return m_started; }
MobileGLResult ClientSession::Start(MG_Config::TransportMode mode, const String& endpoint) {
if (m_started) {
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
// A NAMED ERROR, NEVER A FALLBACK TO MONOLITH. A silent fallback here is exactly the
// "the split lane ran monolith and went green" failure the whole phase is built to
// make impossible (ARCHITECTURE.md 10.3), so every mode this build cannot serve is
// refused by name rather than degraded.
if (mode != MG_Config::TransportMode::InProcess) {
MGLOG_E("MG_Remote client: MOBILEGL_TRANSPORT=%s%s is refused by name - P5 implements "
"`inproc` only, and falling back to monolith would make this lane green for "
"the wrong reason. spawn / unix: / pipe: are P6's",
TransportModeName(mode), endpoint.empty() ? "" : endpoint.c_str());
return MOBILEGL_ERR_UNSUPPORTED;
}
// ---- 1. the control plane and the two bells. The transport owns the bells; THE
// SESSION owns the rings, and the accessors stay off ITransport (contract §3.9).
std::unique_ptr<Transport::InProcessTransport> clientEnd;
std::unique_ptr<Transport::InProcessTransport> serverEnd;
Transport::InProcessTransport::CreatePair(clientEnd, serverEnd);
return StartOverTransportPair(std::move(clientEnd), std::move(serverEnd));
}
MobileGLResult ClientSession::StartOverTransportPair(
std::unique_ptr<Transport::InProcessTransport> clientEnd,
std::unique_ptr<Transport::InProcessTransport> serverEnd) {
if (m_started) {
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
if (clientEnd == nullptr || serverEnd == nullptr) {
MGLOG_E("MG_Remote client: StartOverTransportPair needs both ends of one "
"InProcessTransport::CreatePair");
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
m_clientTransport = std::move(clientEnd);
m_serverTransport = std::move(serverEnd);
m_transport = m_clientTransport.get();
// ---- 2. Hello. Sent before the server accepts: InProcessTransport queues whole
// messages, so one thread can drive both halves of the handshake in order.
const Uint64 fingerprint = CapsAbiFingerprint();
{
::flatbuffers::FlatBufferBuilder builder(512);
auto stamp = builder.CreateString(GIT_COMMIT_HASH_SHORT);
auto hello = ::MobileGL::Wire::CreateHello(
builder, MOBILEGL_PROTOCOL_ABI_MAJOR, MOBILEGL_PROTOCOL_ABI_MINOR, stamp,
/*backendType=*/0u, /*pid=*/SelfProcessId(), /*configBlob=*/0, fingerprint);
auto root = ::MobileGL::Wire::CreateCtrlEnvelope(
builder, ::MobileGL::Wire::CtrlMsg::Hello, hello.Union());
::MobileGL::Wire::FinishCtrlEnvelopeBuffer(builder, root);
const MobileGLResult sent = m_transport->SendFrame(
MobileGLByteSpan{builder.GetBufferPointer(), builder.GetSize()});
if (sent != MOBILEGL_OK) {
Stop();
return sent;
}
}
// ---- 3. the server half: ABI assert, four segments, Welcome.
Server::ServerSession& server = Server::ServerSessionInstance();
const MobileGLResult accepted = server.Accept(*m_serverTransport);
if (accepted != MOBILEGL_OK) {
Stop();
return accepted;
}
// ---- 4. Welcome, and this side's half of the ABI assertion.
{
std::vector<Uint8> frame;
const MobileGLResult received = ReceiveEnvelope(*m_transport, frame, kHandshakeTimeoutMs);
if (received != MOBILEGL_OK) {
MGLOG_E("MG_Remote client: no Welcome within %u ms (rc=%d)", kHandshakeTimeoutMs,
static_cast<int>(received));
Stop();
return received;
}
const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(frame);
// msg_as_Welcome() IS PART OF THE GUARD - flatbuffers' Verifier::VerifyTable is
// `return !table || table->Verify(*this)`, so a NULL union member verifies while
// msg_type() still reports Welcome. See ServerSession::Accept for the same guard.
if (envelope == nullptr || envelope->msg_type() != ::MobileGL::Wire::CtrlMsg::Welcome ||
envelope->msg_as_Welcome() == nullptr) {
MGLOG_E("MG_Remote client: the server's first control frame is not a verifiable "
"Welcome");
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
const ::MobileGL::Wire::Welcome* welcome = envelope->msg_as_Welcome();
const char* theirStamp = welcome->buildFingerprint() == nullptr
? nullptr
: welcome->buildFingerprint()->c_str();
// 4.3: the pid the SERVER stated, taken before any check can abort, so a Fatal line
// can name it too.
m_peerServerPid = static_cast<std::uint32_t>(welcome->serverPid());
// The VERSION before the fingerprint: both would fire, and only one names the cause.
if (welcome->abiMajor() != MOBILEGL_PROTOCOL_ABI_MAJOR ||
welcome->abiMinor() != MOBILEGL_PROTOCOL_ABI_MINOR) {
FatalProtocolVersionMismatch(static_cast<unsigned>(welcome->abiMajor()),
static_cast<unsigned>(welcome->abiMinor()),
theirStamp);
}
if (welcome->abiFingerprint() != fingerprint) {
FatalAbiMismatch("struct shapes", fingerprint, welcome->abiFingerprint(),
theirStamp);
}
// The four SegmentRefs are what a spawn client MAPS (P6). Under inproc the mapping
// already exists, so what they are good for here is the cross-check that the two
// sides agree about the geometry at all - which is the assertion that would
// otherwise first run in P6, on the day it is expensive to be wrong.
using Slot = Transport::SessionSegmentSlot;
const auto agrees = [&](const ::MobileGL::Wire::SegmentRef* ref, Slot slot,
const char* name) {
if (ref == nullptr || ref->sizeBytes() != server.Shm().AnnouncedSize(slot)) {
MGLOG_E("MG_Remote client: Welcome's %s SegmentRef announces %llu bytes, the "
"server mapped %llu",
name,
static_cast<unsigned long long>(ref == nullptr ? 0 : ref->sizeBytes()),
static_cast<unsigned long long>(server.Shm().AnnouncedSize(slot)));
return false;
}
return true;
};
if (!agrees(welcome->cmdRing(), Slot::Cmd, "cmd") ||
!agrees(welcome->stageRing(), Slot::Stage, "stage") ||
!agrees(welcome->replyPool(), Slot::Reply, "reply") ||
!agrees(welcome->eventRing(), Slot::Event, "event")) {
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
}
// ---- 5. attach to the four segments. Under `inproc` this is the SAME mapping booked
// under the client role; under `spawn` it becomes ShmSegment::Adopt of the fds the
// server passed by SCM_RIGHTS, which is why nothing below this line knows which it was.
const MobileGLResult attached =
m_shm.AttachInProcess(server.Shm(), Transport::MemoryRole::Client);
if (attached != MOBILEGL_OK) {
Stop();
return attached;
}
return FinishStartup(&m_clientTransport->PeerDoorbell(),
&m_clientTransport->SelfDoorbell(),
/*startApplyThreadHere=*/true);
}
MobileGLResult ClientSession::StartSpawned() {
if (m_started) {
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
// A rendezvous nobody else can collide with. Independent processes need
// a NAME; making it per-process-per-instant is what stops two runs on
// one machine - which `ctest -j` produces by construction - finding each
// other's server.
// AN ABSTRACT NAME ('@'), not a path under /tmp. An Android app has no
// writable /tmp and the first device run proved it the blunt way: the
// server launched, bind() had nowhere to put the node, and the client
// refused by name 20 s later. The abstract namespace needs no directory,
// no mode bits and no cleanup after a crash, and its reach - the network
// namespace - is exactly one app's processes.
const std::string endpoint = std::string("@mgl-") +
std::to_string(static_cast<long long>(::getpid())) + "-" +
std::to_string(reinterpret_cast<std::uintptr_t>(this));
const MobileGLResult launched =
Server::LaunchServer(std::string(MG_Config::Ipc.ServerPath.c_str()), endpoint,
&m_spawned);
if (launched != MOBILEGL_OK) {
return launched;
}
std::unique_ptr<Transport::SocketTransport> socket;
// The bounded connect retry is what tolerates the server still binding -
// and it is the CLIENT's, not the launcher's. An exhausted budget is a
// NAMED refusal; there is no monolith fallback from here.
const MobileGLResult connected =
Transport::SocketTransport::ConnectTo(endpoint, kSpawnConnectTimeoutMs, socket);
if (connected != MOBILEGL_OK) {
int exitCode = 0;
Server::ReapServer(m_spawned, 2000, &exitCode);
MGLOG_E("MG_Remote client: could not reach the server we launched at \"%s\" "
"(rc=%d, server exit=%d)",
endpoint.c_str(), static_cast<int>(connected), exitCode);
return connected;
}
// THE ONE FACT A MONOLITH OR inproc RUN CANNOT PRODUCE: a pid that is
// not ours. The ConfigLoader marker proves the VALUE resolved; this
// proves the SERVER ROLE LEFT THIS PROCESS, which is the whole claim the
// SPAWN arm of the retrace matrix makes. run_trace_case.cmake requires
// BOTH, so a spawn arm cannot go green on a transport that resolved and
// then quietly ran the server role locally.
const MobileGLResult started = StartOverSocket(std::move(socket));
if (started == MOBILEGL_OK) {
MGLOG_I("MG_Remote client: spawn ARMED - the server role runs in pid %d, reached at "
"\"%s\"",
m_spawned.pid, endpoint.c_str());
}
return started;
}
MobileGLResult ClientSession::StartOverSocket(
std::unique_ptr<Transport::SocketTransport> transport) {
if (m_started) {
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
if (transport == nullptr) {
MGLOG_E("MG_Remote client: StartOverSocket needs a connected transport");
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
m_socketTransport = Move(transport);
m_transport = m_socketTransport.get();
// ---- Hello. The same bytes as inproc; the fingerprint is still compared
// for equality, because under Dial == Fork the child IS the same binary and
// comparing it catches a stale MOBILEGL_IPC_SERVER_PATH (CONTRACT-P6 4.1).
const Uint64 fingerprint = CapsAbiFingerprint();
{
::flatbuffers::FlatBufferBuilder builder(512);
auto stamp = builder.CreateString(GIT_COMMIT_HASH_SHORT);
auto hello = ::MobileGL::Wire::CreateHello(
builder, MOBILEGL_PROTOCOL_ABI_MAJOR, MOBILEGL_PROTOCOL_ABI_MINOR, stamp,
/*backendType=*/0u, /*pid=*/SelfProcessId(), /*configBlob=*/0, fingerprint);
auto root = ::MobileGL::Wire::CreateCtrlEnvelope(
builder, ::MobileGL::Wire::CtrlMsg::Hello, hello.Union());
::MobileGL::Wire::FinishCtrlEnvelopeBuffer(builder, root);
const MobileGLResult sent = m_transport->SendFrame(
MobileGLByteSpan{builder.GetBufferPointer(), builder.GetSize()});
if (sent != MOBILEGL_OK) {
Stop();
return sent;
}
}
// ---- Welcome, and the four announced sizes. THERE IS NO LOCAL SERVER TO
// ASK: the inproc path cross-checks Welcome against ServerSessionInstance()'s
// own mapping, which a6 showed is vacuous against a real peer. Here the wire
// values are the only values, which is what that check has to become on
// every lane (CONTRACT-P6 4.4).
Uint64 announced[4] = {0, 0, 0, 0};
const Uint32 replySlotCount = Transport::kDefaultReplySlotCount;
{
std::vector<Uint8> frame;
const MobileGLResult received =
ReceiveEnvelope(*m_transport, frame, kHandshakeTimeoutMs);
if (received != MOBILEGL_OK) {
MGLOG_E("MG_Remote client: no Welcome from the spawned server within %u ms (rc=%d)",
kHandshakeTimeoutMs, static_cast<int>(received));
Stop();
return received;
}
const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(frame);
if (envelope == nullptr || envelope->msg_type() != ::MobileGL::Wire::CtrlMsg::Welcome ||
envelope->msg_as_Welcome() == nullptr) {
MGLOG_E("MG_Remote client: the spawned server first frame is not a verifiable "
"Welcome");
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
const ::MobileGL::Wire::Welcome* welcome = envelope->msg_as_Welcome();
const char* theirStamp = welcome->buildFingerprint() == nullptr
? nullptr
: welcome->buildFingerprint()->c_str();
// 4.3: the pid the SERVER stated, taken before any check can abort, so a Fatal line
// can name it too.
m_peerServerPid = static_cast<std::uint32_t>(welcome->serverPid());
// The VERSION before the fingerprint: both would fire, and only one names the cause.
if (welcome->abiMajor() != MOBILEGL_PROTOCOL_ABI_MAJOR ||
welcome->abiMinor() != MOBILEGL_PROTOCOL_ABI_MINOR) {
FatalProtocolVersionMismatch(static_cast<unsigned>(welcome->abiMajor()),
static_cast<unsigned>(welcome->abiMinor()),
theirStamp);
}
if (welcome->abiFingerprint() != fingerprint) {
FatalAbiMismatch("struct shapes", fingerprint, welcome->abiFingerprint(),
theirStamp);
}
const ::MobileGL::Wire::SegmentRef* refs[4] = {welcome->cmdRing(), welcome->stageRing(),
welcome->replyPool(),
welcome->eventRing()};
for (int index = 0; index < 4; ++index) {
if (refs[index] == nullptr || refs[index]->sizeBytes() == 0) {
MGLOG_E("MG_Remote client: Welcome SegmentRef %d is missing or zero-sized",
index);
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
announced[index] = refs[index]->sizeBytes();
}
}
// ---- the four descriptors. THIS is the step inproc does not have, and the
// reason SCM_RIGHTS is in this design at all: the segments are anonymous -
// ASharedMemory_create has no filesystem name and memfd / shm_open+unlink
// are not openable either - so the descriptor IS the only key.
//
// The slot travels in the sideband rather than being inferred from arrival
// order, so a reordered or dropped offer is a NAMED mismatch instead of two
// segments quietly swapped.
// Seven offers: four segments, then THREE bell descriptors (slots 4..6).
// Three because each side parks on one and rings another; see ServerMain.
int fds[7] = {-1, -1, -1, -1, -1, -1, -1};
{
struct Sideband {
Uint32 slot;
Uint64 bytes;
};
const auto closeAll = [&fds]() {
for (int& open : fds) {
if (open >= 0) {
::close(open);
open = -1;
}
}
};
for (int received = 0; received < 7; ++received) {
Sideband sideband{};
Uint64 sidebandSize = 0;
int fd = -1;
std::vector<Uint8> scratch(Transport::FdPassing::kMaxSidebandBytes);
MobileGLMutableByteSpan span{scratch.data(), scratch.size()};
const MobileGLResult got =
m_transport->ReceiveFd(&fd, span, &sidebandSize, kHandshakeTimeoutMs);
if (got != MOBILEGL_OK || fd < 0) {
MGLOG_E("MG_Remote client: segment descriptor %d did not arrive (rc=%d)",
received, static_cast<int>(got));
closeAll();
Stop();
return got == MOBILEGL_OK ? MOBILEGL_ERR_PROTOCOL_MISMATCH : got;
}
if (sidebandSize != sizeof(Sideband)) {
MGLOG_E("MG_Remote client: segment offer %d carried %llu sideband bytes",
received, static_cast<unsigned long long>(sidebandSize));
::close(fd);
closeAll();
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
std::memcpy(&sideband, scratch.data(), sizeof(Sideband));
const bool isSegment = sideband.slot < 4;
if (sideband.slot >= 7 || fds[sideband.slot] >= 0 ||
(isSegment && sideband.bytes != announced[sideband.slot])) {
MGLOG_E("MG_Remote client: segment offer names slot %u with %llu bytes; "
"Welcome announced a different size or the slot is already filled",
sideband.slot, static_cast<unsigned long long>(sideband.bytes));
::close(fd);
closeAll();
Stop();
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
fds[sideband.slot] = fd;
}
// ---- adopt and map. The same Adopt + Map every inproc run has
// exercised since P5; only the origin of the descriptor is new.
const MobileGLResult adopted = m_shm.AdoptFromDescriptors(
fds, announced, replySlotCount, Transport::MemoryRole::Client);
if (adopted != MOBILEGL_OK) {
closeAll();
Stop();
return adopted;
}
// The four segment descriptors now belong to m_shm. The two bells
// belong to the doorbells, which own and close them.
//
// WHICH BELL IS WHICH IS THE SESSION'S KNOWLEDGE, exactly as under
// inproc: slot 4 is the pair end whose WRITE wakes the server, slot 5
// is the one this side POLLS.
// PARK ON ONE END, RING THE OTHER - the same split the server makes,
// and for the same reason: a single-fd bell rings the PEER, so it
// cannot wake its own waiter.
// fds[4] ring the SERVER (ring-only, we never park on it)
// fds[5] our park end
// fds[6] ring OURSELVES
m_socketPeerBell = MakeUnique<Transport::SocketDoorbell>(-1, fds[4], 1, true);
// Built into a TYPED pointer first: the witness is SocketDoorbell's, and the member
// is a Doorbell so that the inproc path can put a CondVarDoorbell in it.
auto selfBell = MakeUnique<Transport::SocketDoorbell>(fds[5], fds[6], 1, true);
// `dl`: THE DEATH WITNESS, and it has to be a descriptor this side does not also
// write to. Our own bell is a socketpair we hold BOTH ends of - slot 5 to park on,
// slot 6 to ring ourselves - so it can never hang up however dead the server is. The
// control socket's far end is held only by the server, so its hangup IS the death.
//
// Passing the fd rather than the transport keeps the ownership honest: the bell polls
// it for hangup alone and never reads it, and SocketTransport goes on owning and
// closing it. CONTRACT-P6 D5c.
selfBell->SetDeathWitness(m_socketTransport->StreamFd());
m_socketSelfBell = Move(selfBell);
}
// `cp`: from here the twelve EGL forwarders cross the socket instead of
// being posted into a mailbox this process does not own. Installed BEFORE
// FinishStartup, because FinishStartup's caps pump can already trigger
// one.
Server::ServerLoopInstance().SetRemoteControlSink(&RemoteControlSinkThunk, this);
// The apply thread IS ALREADY RUNNING, in the other process: ServerMain
// started it before it sent the first descriptor. Starting one here would
// put a second applier on a ring that already has one.
return FinishStartup(m_socketPeerBell.get(), m_socketSelfBell.get(), false);
}
MobileGLResult ClientSession::RemoteControlSinkThunk(void* user,
Server::SurfaceControlFrame& frame) {
return static_cast<ClientSession*>(user)->RunRemoteSurfaceControlFrame(frame);
}
MobileGLResult ClientSession::RunRemoteSurfaceControlFrame(Server::SurfaceControlFrame& frame) {
if (m_transport == nullptr) {
return MOBILEGL_ERR_NOT_INITIALIZED;
}
// THE CLIENT MINTS, always, dense from 1 (CONTRACT-P6 §6.3). The server's
// local mint exists for unnumbered LOCAL posts; a wire request that let
// the server renumber it would get back a reply it cannot correlate.
if (frame.seq == 0) {
frame.seq = ++m_remoteControlSeq;
}
::flatbuffers::FlatBufferBuilder builder(512);
const MG_Remote::SurfaceWireError encoded = MG_Remote::EncodeSurfaceOpFrame(frame, &builder);
if (encoded != MG_Remote::SurfaceWireError::None) {
// A NAMED refusal, not a dropped op. InprocOnlyOpOnTheWire is the
// live one: three of the twelve forwarders ride the frame channel
// without a wire kind (CONTRACT-P6 §2), and a spawn client that
// reaches one has found a gap rather than a transport error.
MGLOG_E("MG_Remote client: surface op kind %d cannot cross the wire (%s)",
static_cast<int>(frame.kind), MG_Remote::SurfaceWireErrorName(encoded));
return MOBILEGL_ERR_UNSUPPORTED;
}
// ONE CONTROL OP AT A TIME. The twelve forwarders are already
// caller-serialised on the server's m_callerMutex under inproc; the same
// discipline has to hold here or two replies race for one correlation.
const std::lock_guard<std::mutex> lock(m_remoteControlMutex);
const MobileGLResult sent = m_transport->SendFrame(
MobileGLByteSpan{builder.GetBufferPointer(), builder.GetSize()});
if (sent != MOBILEGL_OK) {
return sent;
}
// The reply. A BOUNDED wait whose expiry is NOT fatal (CONTRACT-P6 §5.4
// D5b): a peer that is gone is a different fact from a peer that is slow,
// and only the doorbell's death latch may say which.
for (;;) {
std::vector<Uint8> reply;
const MobileGLResult received =
ReceiveEnvelope(*m_transport, reply, kRemoteControlTimeoutMs);
if (received != MOBILEGL_OK) {
// `dl` (D5b): THE EXPIRY IS NOT FATAL AND IT IS NOT ONE ANSWER. The transport
// already distinguishes the two states this wait can end in, and the contract
// says they must stay distinguished without a threshold:
//
// TRANSPORT_CLOSED - the control socket returned EOF. Only the server held the
// far end, so it is gone. That is the device-loss fact, taken from a
// descriptor.
// TIMEOUT - nothing arrived in the budget, and the socket is still open. The
// peer is ALIVE AND SILENT: wedged, frozen, SIGSTOP'd, or merely slower than
// the budget. 5.4 forbids calling that a death, so it gets a NAME instead.
// The bell is asked anyway, because a hangup noticed by the ring side counts
// here too.
if (received == MOBILEGL_ERR_TRANSPORT_CLOSED) {
LatchDeviceLost("the control stream reached EOF while a reply was owed");
} else if (const Transport::Doorbell* bell = m_producer.SelfDoorbell();
bell != nullptr && bell->PeerHungUp()) {
LatchDeviceLost("a control reply timed out and the peer had hung up");
} else {
MGLOG_E("MG_Remote client: the server is ALIVE BUT SILENT - no SurfaceReply "
"for %s seq %llu within %u ms and the control stream is still open. "
"This is NOT device loss (CONTRACT-P6 5.4): a frozen or merely slow "
"peer produces no hangup, and only a hangup may arm the latch. If "
"this repeats, the server is wedged rather than gone.",
Server::SurfaceControlOpName(frame.kind),
static_cast<unsigned long long>(frame.seq), kRemoteControlTimeoutMs);
}
MGLOG_E("MG_Remote client: no SurfaceReply for seq %llu within %u ms (rc=%d)",
static_cast<unsigned long long>(frame.seq), kRemoteControlTimeoutMs,
static_cast<int>(received));
return received;
}
const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(reply);
if (envelope == nullptr) {
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
if (envelope->msg_type() == ::MobileGL::Wire::CtrlMsg::CapsSnapshot) {
// The server republishes caps from inside its MakeCurrent
// dispatch (a6 row A4-30), so a snapshot can arrive BEFORE the
// reply to the very op that produced it. Adopting it here rather
// than dropping it is what keeps R-12's "a second arrival IS the
// invalidation" true on this path too.
if (const auto* snapshot = envelope->msg_as_CapsSnapshot()) {
AdoptCapsSnapshot(snapshot);
}
continue;
}
if (envelope->msg_type() == ::MobileGL::Wire::CtrlMsg::Fatal) {
// `dl` step three: the server published a SessionFault before it aborted, so this
// is a death that NAMES ITSELF instead of arriving as a bare EOF. Log the family
// and detail, latch device-lost from it, and report the op declined - the same
// answer a hangup gives, now with a cause the guest's log can read.
if (const auto* fatal = envelope->msg_as_Fatal()) {
const char* fam = fatal->family() ? fatal->family()->c_str() : "<none>";
const char* msg = fatal->message() ? fatal->message()->c_str() : "";
MGLOG_E("MG_Remote client: the server published a SessionFault before dying - "
"Fatal family %s: %s", fam, msg);
}
LatchDeviceLost("the server published a SessionFault and then aborted");
frame.ok = false;
return MOBILEGL_ERR_TRANSPORT_CLOSED;
}
if (envelope->msg_type() != ::MobileGL::Wire::CtrlMsg::SurfaceReply ||
envelope->msg_as_SurfaceReply() == nullptr) {
MGLOG_E("MG_Remote client: expected a SurfaceReply, got message type %d",
static_cast<int>(envelope->msg_type()));
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
const ::MobileGL::Wire::SurfaceReply* wire = envelope->msg_as_SurfaceReply();
if (wire->seq() != frame.seq) {
MGLOG_E("MG_Remote client: SurfaceReply names seq %llu, we asked for %llu",
static_cast<unsigned long long>(wire->seq()),
static_cast<unsigned long long>(frame.seq));
return MOBILEGL_ERR_PROTOCOL_MISMATCH;
}
MG_Remote::DecodeWireSurfaceReply(*wire, &frame);
return MOBILEGL_OK;
}
}
// The half of startup that is IDENTICAL for inproc and spawn: the ring
// producer, the reply pool, the event ring, the segment table, the encoder,
// the first CapsSnapshot and the emitter tables. Extracted by `sm` so the
// spawn path cannot drift from the shape P5 spent five packages settling -
// everything here is below the line where "which transport" stopped
// mattering.
//
// `startApplyThreadHere` is the one policy difference, and it is not a
// transport question: under inproc the client is what starts the server
// role, because there is no server-side main to do it. Under spawn there
// IS one, and it started the apply thread before it ever sent Welcome.
MobileGLResult ClientSession::FinishStartup(Transport::Doorbell* peerBell,
Transport::Doorbell* selfBell,
bool startApplyThreadHere) {
Transport::RingControl* control = m_shm.CmdControl();
m_cmd = Transport::RingProducer(control, m_shm.CmdRingBase(), m_shm.CmdRingCapacity(),
Transport::RingCursorSet::Cmd);
// NO STAGE RING. SEG_STAGE is package w1's encoder-local LINEAR ALLOCATOR:
// a staged byte run carries no RingRecordHeader, nothing consumes SEG_STAGE,
// and the allocator reclaims on retiredSeq. A RingProducer over
// RingCursorSet::Stage would publish stageHead with nothing advancing the
// two tails, so FreeBytes() would fall to zero the first time the head
// lapped the capacity and never recover - a guaranteed hang. See
// RingControl's stage triple in Ring.h.
if (!m_cmd.Valid()) {
Stop();
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
// PeerDoorbell() is the bell the SERVER parks on and this side rings; SelfDoorbell() is
// this side's own. Which is which is the session's knowledge, not the transport's.
m_producer.Attach(control, &m_cmd, peerBell, selfBell, SpinUsFromConfig());
m_replies = Transport::ReplySlotPool(m_shm.ReplyBase(), m_shm.ReplyBytes(),
m_shm.ReplySlotCount());
m_events = Transport::EventRingConsumer(m_shm.EventControl(), control,
m_shm.EventRingBase(), m_shm.EventRingCapacity(),
m_shm.EventSegmentBase());
// P5e (ra, §2.6): the drain's other half. A server parked on a full SEG_EVENT is woken
// by the drain that emptied it, not by the next thing this client happens to publish.
m_events.SetServerDoorbell(peerBell);
if (!m_replies.Valid() || !m_events.Valid()) {
Stop();
return MOBILEGL_ERR_INVALID_ARGUMENT;
}
m_barrierArmed = VerbBarrierFromConfig();
if (!m_barrierArmed) {
MGLOG_W("MG_Remote client: MOBILEGL_IPC_VERB_BARRIER=0 - this is R-1's NEGATIVE "
"CONTROL and is EXPECTED to be red. 31 of the 63 PipeInputs fields are still "
"pulled from a live GLContext by the client's residual fill, so a free-running "
"queue lets the server read a FUTURE value of them");
}
// ---- 6. the client's segment table. IT MUST NOT INSTALL THE PROCESS RESOLVER: there is
// exactly one gMGPipeSegmentResolver per process, the SERVER role owns it (table 3), and
// the client never resolves a span at all - it only ever writes Ptr = nullptr (R-2's
// rule B). Two roles racing on that one inline variable is precisely what the server's
// InstallProcessResolver asserts against.
//
// The Install calls themselves are package w1's and are named-Fatal stubs until w1
// lands; see ServerSession::Accept for why they are called anyway.
m_segments.Install(Wire::kSegCmd,
Wire::SegmentView{m_shm.CmdRingBase(), m_shm.CmdRingCapacity()});
m_segments.Install(Wire::kSegStage,
Wire::SegmentView{m_shm.StageBase(), m_shm.StageBytes()});
m_segments.Install(Wire::kSegReply,
Wire::SegmentView{m_shm.ReplyBase(), m_shm.ReplyBytes()});
m_segments.Install(Wire::kSegEvent,
Wire::SegmentView{m_shm.EventSegmentBase(),
m_shm.AnnouncedSize(Transport::SessionSegmentSlot::Event)});
// nullptr for the stage producer, and that is the honest value: c0's
// signature predates w1's ruling that SEG_STAGE is a linear allocator, and
// the encoder reaches its bytes through the SegmentTable above. Handing it
// a live RingProducer over a cursor triple nobody consumes would be the
// half-wired shape this session exists not to have.
m_encoder = Wire::PipeWireEncoder(control, &m_cmd, nullptr, &m_segments);
m_encoder.SetStageRetirementDoorbell(m_producer.SelfDoorbell());
// P5e (ra, §2.6): the stage bell is a client wait and every client wait drains. The
// encoder owns the park; the session owns SEG_EVENT, so the session lends it a drain.
m_encoder.SetStageWaitHook(
+[](void* self) { DrainEventRing(static_cast<ClientSession*>(self)->Events()); }, this);
// ---- 7. the first CapsSnapshot, if the server had a backend to publish one from.
// ONE DRAIN, ONE ADOPTER (c1): PumpControlPlane below is the only thing in the client
// that turns a CapsSnapshot into a CapsMirror generation, so R-12's "a second arrival
// IS the invalidation" lives in exactly one place. s1's step here used to stop at
// "the snapshot arrived and is verifiable"; it now goes all the way, through the same
// function every later arrival goes through.
if (PumpControlPlane() == 0) {
MGLOG_W("MG_Remote client: the handshake carried no CapsSnapshot - the caps mirror is "
"a PLACEHOLDER until one arrives. Every caps read until then answers a "
"default and says so");
}
// BOTH, AND m_started FIRST. `Active()` is what the integration lane's skip reads and
// `m_started` is what `EmitAndWait` reads, and c1's round-1 rewrite of this function
// set only the second of the two - so a fully-handshaken session with an apply thread
// running and a caps mirror adopted took Fatal{NoClientSession, "Clear"} on its very
// first verb, which is the most confusing possible spelling of "the session is up".
// The order matters for the same reason it does at the other end: `Active()` hands a
// caller a session it may immediately emit on, so the flag that permits emitting has
// to be true before the pointer that grants access to it is published. `Stop()` takes
// them down in the mirror order (m_started = false, then g_active = nullptr).
m_started = true;
g_active = this;
// D1c: THE SESSION-LIVE AND APPLY-THREAD FACTS, stated where they become true.
//
// MGPipeApplierReset's layer-2 guard used to ask ClientSession::Active() != nullptr,
// which no SERVER process can ever answer yes to - so the guard was compiled in and
// permanently disarmed there. MGPipeSessionLive() is the same question asked in a way
// both roles can answer, and the probe hands MG_Backend the one thread fact it cannot
// derive: whether the CALLING thread is inside the applier.
MG_Pipe::MGPipeSetSessionLive(true);
// ServerLoop::OnApplyThread, NOT ApplyThreadIsInsideApplier - two different questions,
// and installing the wrong one turned every GL-thread call into a role violation while
// the applier happened to be busy. Measured: the inproc retrace died on
// Fatal{RoleViolation, "MGPipeSlots"} raised from the GL thread. "Am I the apply
// thread" is what the guards ask; "is the apply thread inside the applier" is R-1's
// mutual-exclusion probe and is about a DIFFERENT thread.
MG_Pipe::MGPipeSetApplyThreadProbe(&Server::ServerLoop::OnApplyThread);
LogMemory("handshake");
// ---- 8. and only now the apply thread. It is package v1's ServerLoop: it names the
// thread mgl-srv-apply, applies MOBILEGL_IPC_SERVER_AFFINITY and logs the RESOLVED
// mask. Under `inproc` the client is what starts the server role, which is why this
// call is here rather than in some server-side main.
if (startApplyThreadHere) {
Server::ServerSession& server = Server::ServerSessionInstance();
const MobileGLResult running = Server::ServerLoopInstance().Start(server);
if (running != MOBILEGL_OK) {
Stop();
return running;
}
}
// ---- 9. AND ONLY NOW THE THIRTY-SEVEN WIRE EMITTERS (R-17). This is the line that
// arms `integration-split`: the 21 `DirectGLES.Split.*` entries skip on
// `ClientSession::Active() == nullptr`, and every one of the four arming facts is true
// at exactly this point and at no earlier one.
//
// IT IS LAST, AND EACH OF THE FOUR REASONS IS A DIFFERENT FAILURE:
// - after Hello/Welcome (step 2-4), or an emitter would publish into a ring the peer
// has not mapped;
// - after the first CapsSnapshot (step 7), because R-8's liveness gates read the caps
// mirror and a PLACEHOLDER mirror consumes nothing - a record emitted before it
// would go to a server this client has not been told consumes that family;
// - after ServerLoop::Start (step 8), because EmitAndWait BLOCKS on appliedSeq and
// with no apply thread nothing advances it: the first resource_create would spend
// the whole kBarrierTimeoutMs in the barrier and then Fatal{BarrierTimeout};
// - on THIS thread, the one that called MG_Backend::Init(), because it is the GL
// thread and table 3 makes gPipeInputs its to touch while the barrier holds.
// The publication is safe without a fence because the apply thread never reads these
// tables - the server decodes straight into MGPipeApply* - and this thread wrote them
// before it can reach any GL entry point.
InstallClientWireTables();
return MOBILEGL_OK;
}
void ClientSession::Stop() {
// FIRST, BEFORE ANYTHING ELSE GOES AWAY (R-17 / codex 4). Every later step here frees
// something an emitter dereferences - the rings, the segments, the transports - so a
// routed GL-thread call that arrives during teardown must not run the applier on the
// caller and must not reach a half-freed ring. Round 2 reinstalled the monolith adapters
// HERE, which is running the applier on the caller - the forbidden path table 3 draws.
// Uninstall now RAISES A FLAG and leaves the wire rows in place; the next routed call
// aborts by name (Fatal{ClientTablesUninstalled}) inside RequireSession before it touches
// anything. The monolith adapters go back only at the END of teardown
// (ReinstallMonolithAfterTeardown), for the at-exit ~BufferObject deletes that reach a
// process with no session at all - and by then the rings are gone, so the applier a
// monolith adapter runs is a defined no-op rather than a use-after-free.
UninstallClientWireTables();
if (!m_started) {
// Start's own failure paths land here with a half-built session. FIVE of them are
// reached AFTER ServerSession::Accept has already returned OK, so tearing down
// only the client half is not enough and gets three things wrong at once: the
// server keeps its four mappings and stays m_accepted, so Accept's own guard
// refuses every later Start and the process can never open a session again; the
// process-wide segment resolver stays installed; and resetting m_serverTransport
// destroys a transport that ServerSession::m_transport and its two Doorbell*
// still point at. The server closes FIRST, in the same order the started path
// gets right, and only then do the transports go.
m_producer.Detach();
m_shm.Close();
Server::ServerSessionInstance().Close();
m_clientTransport.reset();
m_serverTransport.reset();
m_transport = nullptr;
// The rings are gone; put the monolith adapters back for a process that will make no
// more routed calls except, possibly, at-exit deletes (codex 4).
ReinstallMonolithAfterTeardown();
return;
}
// TABLE 3's TEARDOWN ORDER, and every step of it is load-bearing.
//
// 1. publish and let the server drain. Bounded: a lost record must be a red lane, not
// a hung exit.
Transport::RingControl* control = m_shm.CmdControl();
if (control != nullptr) {
// The PRODUCER's own last-published seq, not RingControl::submittedSeq. Ring.h:72-77
// permits submittedSeq to be published lazily and Ring.h:243 encourages batching
// the publish, so the shared watermark is allowed to lag the emitter - and a drain
// that waited for `appliedSeq >= submittedSeq` would then under-wait and free an
// emitter-owned var-tail while a record still names it. With the verb barrier armed
// the two are equal; under MOBILEGL_IPC_VERB_BARRIER=0, R-1's negative control that
// the phase has to run once, they are not.
const Uint64 submitted = m_producer.LastPublishedSeq();
m_producer.PublishAndNotify(submitted);
if (submitted != 0 &&
m_producer.WaitForApplied(submitted, kDrainTimeoutMs) != Transport::SessionWait::Reached) {
MGLOG_E("MG_Remote client: the server did not drain to seq %llu within %u ms; "
"tearing down anyway, and anything an emitter still owns is freed below "
"AFTER the join, which is what keeps that from being a use-after-free",
static_cast<unsigned long long>(submitted), kDrainTimeoutMs);
}
}
// 2. Doorbell::Kill(). THE ONLY thing that can wake an apply thread parked on
// kWaitForever (CondVarDoorbell::Kill): a Notify is consumed by one Park, after which
// Doorbell::Wait re-tests a condition nothing published, finds the bell alive and
// parks again, forever. InProcessChannel::Close kills both bells.
if (m_transport != nullptr) {
m_transport->Shutdown();
}
// 3. JOIN, bounded - package v1's ServerLoop::Stop, which also destroys the server's
// private BackendObject on that thread before it exits.
Server::ServerLoopInstance().Stop();
// 4. and ONLY NOW may anything an emitter owns be released: a var-tail still
// referenced by an unapplied record is a use-after-free the join is what prevents.
LogMemory("teardown");
LogWireLedger();
m_producer.Detach();
m_encoder = Wire::PipeWireEncoder();
m_events = Transport::EventRingConsumer();
m_replies = Transport::ReplySlotPool();
m_cmd = Transport::RingProducer();
m_shm.Close();
Server::ServerSessionInstance().Close();
m_clientTransport.reset();
m_serverTransport.reset();
m_transport = nullptr;
m_started = false;
// P5e (ra, §1): the LATCH GOES DOWN WITH THE SESSION. It is "what the first caps
// adoption of THIS session said", and a session that starts again - the same singleton,
// a second Start - must take it again from that session's own first snapshot rather
// than inherit a verdict about a server that is gone. The present serial goes with it
// for the same reason: the credit's id space belongs to the session that paces on it.
m_runAheadArmed = false;
m_runAheadLatched = false;
m_presentsSent = 0;
if (g_active == this) {
g_active = nullptr;
// Mirror order, and the probe goes with it: a dangling function pointer into a
// torn-down session is a worse answer than "there is no applier".
MG_Pipe::MGPipeSetSessionLive(false);
MG_Pipe::MGPipeSetApplyThreadProbe(nullptr);
}
// AND ONLY NOW the monolith adapters go back (codex 4): every ring an emitter would have
// used is freed above, so from here a routed call - an at-exit ~BufferObject delete - runs
// the applier exactly as it does under monolith, which is the correct answer for a
// process that no longer has a session. During the whole span above, the raised flag made
// any routed call abort by name instead.
ReinstallMonolithAfterTeardown();
// P6: the server we launched. Closing the transport is what it sees as
// EOF and EOF is its whole exit condition, so the order is transport
// first, reap second - and the reap is BOUNDED, because a server that
// will not go is a different fact from one that is slow and only the
// exit code can say which.
if (m_spawned.pid >= 0) {
if (m_socketTransport) {
m_socketTransport->Shutdown();
}
int exitCode = 0;
if (Server::ReapServer(m_spawned, 3000, &exitCode) != MOBILEGL_OK) {
MGLOG_W("MG_Remote client: the spawned server (pid %d) did not exit within 3 s",
m_spawned.pid);
} else if (exitCode != 0) {
MGLOG_W("MG_Remote client: the spawned server exited %d", exitCode);
}
}
Server::ServerLoopInstance().SetRemoteControlSink(nullptr, nullptr);
}
Wire::PipeWireEncoder& ClientSession::Encoder() { return m_encoder; }
CapsMirror& ClientSession::Caps() { return CapsMirrorInstance(); }
// PACKAGE c1's. The barrier's wait and the reply's wait are ONE wait (R-3/R-5), which is
// what makes a blocking ReadPixels, MapPersistent's decline and the four Bool acceptances
// cost zero extra round trips - and the client may not re-derive any of those four answers
// locally. s1 supplies the four primitives it composes from: Encoder(), Producer(),
// WaitForApplied() and ReadReply().
//
// THE ORDER IS ENCODE -> PUBLISH+NOTIFY -> WAIT -> READ REPLY, and it is not negotiable.
// Splitting the wait from the read is how a package ends up answering an acceptance
// question locally, which is the c0f/c0g defect P4a paid two contract corrections for; and
// "always accept" is ID-39's 66 lost DirectVulkan uploads with a wire in between.
Uint64 ClientSession::EmitAndWait(MG_Pipe::MGPWireOp op, const void* payload, Uint64 payloadBytes,
const void* varTail, Uint64 varTailBytes, void* replyOut,
Uint64 replyBytes, Int32* statusOut, Uint64* replySizeOut) {
// One tail is the two-tail form with one entry (P5b d1). Nothing is duplicated: the
// barrier policy below has exactly one body, and the encoder's one-tail EncodeRecord is
// itself defined as the tails form with tailCount <= 1.
const Wire::WireTail tail{varTail, varTailBytes};
return EmitAndWaitTails(op, payload, payloadBytes, varTail != nullptr ? &tail : nullptr,
varTail != nullptr ? 1u : 0u, replyOut, replyBytes, statusOut,
replySizeOut);
}
Uint64 ClientSession::EmitAndWaitTails(MG_Pipe::MGPWireOp op, const void* payload,
Uint64 payloadBytes, const Wire::WireTail* tails,
Uint32 tailCount, void* replyOut, Uint64 replyBytes,
Int32* statusOut, Uint64* replySizeOut,
Bool wantReply) {
Uint64 varTailBytes = 0;
for (Uint32 i = 0; i < tailCount; ++i) varTailBytes += tails[i].Size;
if (statusOut != nullptr) *statusOut = Wire::ReplySink::kStatusError;
if (replySizeOut != nullptr) *replySizeOut = 0;
if (!m_started) {
SessionFail(MGFatalFamily::NoClientSession, "MGPipe: Fatal{NoClientSession, \"%s\"} - EmitAndWait on a session that has "
"not started. There is no fall-through: a record that could not be emitted "
"is a verb that did not happen",
Wire::WireOpName(op));
}
// R-1's INVARIANT, AS A RUNTIME CHECK RATHER THAN A SENTENCE - but only while the
// per-record barrier is the fencing model. With MOBILEGL_IPC_BATCH_WAITS=1 the
// intended shape is exactly "the apply thread is inside the applier while the GL
// thread emits the next value record", and the check would fire on the first batch:
// its protection is already carried by the disjoint-field model (record-supplied
// fields are written only by the applier from records and are never filled by the
// client while the wire is live; BARRIER-PULLED fields are written only by the
// client's residual fill and are read only at the pull-verbs, whose own wait makes
// the fill quiescent during that apply). With the batch off, the original check
// stands as written.
if (MG_Config::Ipc.BatchWaits == 0 && ApplyThreadIsInsideApplier()) {
SessionFail(MGFatalFamily::BarrierViolation, "MGPipe: Fatal{BarrierViolation, \"%s\"} - the apply thread is inside the "
"applier while the GL thread is emitting. R-1 makes at most one of them "
"runnable, which is what keeps one process-wide gPipeInputs legal",
Wire::WireOpName(op));
}
Uint64 seq = m_encoder.EncodeRecord(op, payload, payloadBytes, tails, tailCount);
if (seq == Wire::kInvalidSeq) {
// EncodeRecord already refused individually oversized records. This one fits,
// but appliedSeq may be ahead of retiredTail: wait for actual reclaimable space,
// including the wrap pad. Prior EmitAndWait calls have published every record.
Wire::WireRecordLayout layout{};
Wire::MGPipeWireRecordLayout(op, payload, layout);
const Uint64 toEnd = m_cmd.Capacity() - m_cmd.LocalHead() % m_cmd.Capacity();
const Uint64 needed = layout.TotalBytes + (toEnd < layout.TotalBytes ? toEnd : 0);
const BarrierWaitScope waiting;
const auto wait = m_producer.WaitForCmdSpace(needed, kBarrierTimeoutMs);
if (wait != Transport::SessionWait::Reached) {
SessionFail(MGFatalFamily::RetirementWaitFailed, "MGPipe: Fatal{RetirementWaitFailed, \"SEG_CMD\"} - %s needs %llu "
"reclaimable bytes; the retirement wait ended on %s",
Wire::WireOpName(op), static_cast<unsigned long long>(needed),
wait == Transport::SessionWait::ShutDown ? "shutdown" : "timeout");
}
// P5e (ra, §2.6): EVERY WAIT EXIT DRAINS. The cmd-space wait is one of the two
// safety nets under run-ahead (the stage bell is the other), and a client parked
// here without draining is the other half of the flow-control deadlock: the server
// stops applying on a full event ring, so retiredSeq stops moving, so this wait
// never completes. One drain on the way out closes it.
DrainEventRing(m_events);
seq = m_encoder.EncodeRecord(op, payload, payloadBytes, tails, tailCount);
if (seq == Wire::kInvalidSeq) {
SessionFail(MGFatalFamily::RingOverrun, "MGPipe: Fatal{RingOverrun, \"SEG_CMD\"} - %s refused after sufficient "
"space retired", Wire::WireOpName(op));
}
}
// Publish the head, record submittedSeq, THEN ring - in that order, which is
// SessionProducer's one job and RingTest.cpp:446's pin. Notify-then-publish loses the
// wakeup.
m_producer.PublishAndNotify(seq);
// Does this row own a reply slot? kMGPipeCallFlags IS THE SINGLE SOURCE OF TRUTH
// (R-16 / ID-31) - fourteen rows now, because the four Bool acceptance entry points
// gained the flag. Asking the catalogue rather than the caller is what stops a caller
// that forgot to pass a buffer from silently turning an answer into a guess.
//
// P5e (ra) ADDS ONE CALLER-SIDE CONJUNCT AND NO SECOND SOURCE OF TRUTH: `wantReply`.
// The catalogue still says which rows CARRY a slot; a caller that passes false says it
// will not read this one (resource_subdata's buffer half, §2.5 - the only such caller).
// The server posts either way, so the wire is unchanged and the row keeps its flag.
const Bool rowCarriesReplySlot =
(MG_Pipe::MGPipeCallFlagsFor(op) & static_cast<Uint32>(MG_Pipe::kReplySlot)) != 0;
const Bool ownsReplySlot = rowCarriesReplySlot && wantReply;
// ---- THE P5e WAIT RULE (CONTRACT-P5E §2.3) ---------------------------------------
//
// IT STANDS BEFORE THE BATCH SKIP AND REPLACES IT WHOLE, rather than adding a clause to
// it. The batch skip is a rule about CALL CLASSES ("a set/CSO/object record carries its
// whole value in the payload"); the wait class is a rule about WHAT AN APPLY READS, and
// it is generated from the same PipeCalls.def row the class comes from
// (MGPipeWaitClassFor, c0e). Two rules layered would mean a row could be skipped by the
// class rule and waited by the column, and the column is the one the SERVER's
// MGPipeBarriered reads - so the two halves of the wire would disagree about whether
// the client is parked behind this record, which is the single fact §4.4's exemptions
// and §3.3's detector both rest on.
//
// WITH RUN-AHEAD DISARMED NOTHING BELOW RUNS and the file's original shape continues -
// Magma, a monolith transport, MOBILEGL_IPC_RUN_AHEAD=0 and every build before the
// integration commit take the old path byte for byte, which is what makes RUN_AHEAD=0
// a pure wait-rule A/B on identical server code (§5.8).
if (RunAheadArmed() && !ownsReplySlot) {
MG_Pipe::MGPipeWaitClass waitClass = MG_Pipe::MGPipeWaitClassFor(op);
// §2.5's named relaxation, and the ONLY place a static column answer is overridden:
// a kWaitReply row whose caller does not want the answer has nothing to wait FOR.
// It is spelled here rather than in the column because the column is per-op and
// this is per-call - the texture half of the same row still waits.
if (!wantReply && waitClass == MG_Pipe::kWaitReply) waitClass = MG_Pipe::kWaitNone;
switch (waitClass) {
case MG_Pipe::kWaitNone:
// Published and gone. Rule F is what makes this legal: the apply of an
// unbarriered record names no client memory at all (§3, §4, §5).
return seq;
case MG_Pipe::kWaitPresent:
// The credit wait already ran, in EmitPresent, BEFORE the encode (§2.4). There
// is nothing left to do here and waiting would turn the credit into a barrier.
return seq;
case MG_Pipe::kWaitApplied:
// §2.2's barriered rows: applier_reset, generate_mipmap (until tx2 lands its
// VerbMipRes arm), set_storage_block_binding, the five XFB span verbs and the
// CopyTex endpoint. Each still pulls a row or probes a registry, and the
// client's wait is exactly what keeps P5C's semantics legal for it (ruling 4).
// Falls through to the wait below.
break;
case MG_Pipe::kWaitReply:
case MG_Pipe::kWaitClassCount:
// Unreachable: `ownsReplySlot` is false here, and gen_pipe refuses a kWaitReply
// row without a slot and a kReplySlot row that does not wait (c0e's three
// negative controls). Treated as a wait rather than as a skip, because the
// wrong answer to "does this hang" is the recoverable one.
break;
}
}
// MOBILEGL_IPC_BATCH_WAITS (default 1): a value-class record is published WITHOUT
// waiting for its own apply. The barrier's one load-bearing reader is the backend
// sync that pulls the object-class fields (CONTRACT-P5 table 2's remaining rows), and
// those reads happen only at the kCtxVerb applies - draw / clear / blit / dispatch /
// readback / XFB - plus the screen and query classes, and EVERY ONE OF THOSE STILL
// WAITS below (as does every reply-slot row, whose answer the client consumes). So
// the pulled fields are exactly as fresh at every read point as the per-record
// barrier made them: between two waits the residual fill may move a field, but no
// apply is reading it in between, and the next pull-verb's fill runs after the
// previous pull-verb's apply was waited - the R-1 fence posts are untouched, only
// the number of round trips between them changes. Set / CSO / object records carry
// their whole value in the payload and are consumed at the next (waited) sync, which
// the in-order ring guarantees precedes that sync's apply.
//
// WITH ONE NAMED EXCEPTION, FOUND BY ITS OWN FATAL (P5d round 3): generate_mipmap is
// catalogued kCtxObject, but its sink is the backend's GenerateMipmap, which reads
// MGB_CTX->GetActiveTextureUnit() and the unit's binding slot - residual inputs whose
// freshness is the CLIENT's verb serial. Published without a wait, the record sits in
// the ring while this thread runs the next verb's MGPipeValidateForVerb, which moves
// that serial and withdraws the server stamp; the apply thread then reads the unit
// stale and aborts Fatal{UnmigratedPipeInput, "GetActiveTextureUnit@<next verb>"}
// (F1WireScenario.GenerateMipmap*Pixels, reproduced on the gate tree once the round-3
// spin no longer read the clock). So it waits, exactly as the four stamping verbs
// do. The rule this encodes: a record may skip its wait only if its apply reads
// nothing the residual fill writes - the value carried in the payload is the whole
// input. No other kCtxObject row has a backend body behind it that reads MGB_CTX
// (set_texture_params, resource_subdata, resource_readback and get_texture_image
// own reply slots and wait anyway; the resource_* transfers and object_death resolve
// by handle).
//
// AND IT IS DISARMED WHOLE UNDER RUN-AHEAD (P5e §2.3): the wait class above is the
// rule there, and a second skip rule reading a different column is how the two halves
// of the wire end up disagreeing about whether the client is parked. Written as a
// conjunct here rather than left to "the classes happen not to overlap", because the
// classes overlapping is one PipeCalls.def row away at any time.
if (!ownsReplySlot && !RunAheadArmed() && MG_Config::Ipc.BatchWaits != 0 &&
op != MG_Pipe::MGPWireOp::GenerateMipmap) {
const MG_Pipe::MGPipeCallClass callClass = MG_Pipe::MGPipeCallClassFor(op);
if (callClass == MG_Pipe::kCtxState || callClass == MG_Pipe::kCtxCso ||
callClass == MG_Pipe::kCtxObject) {
return seq;
}
}
if (!m_barrierArmed && !ownsReplySlot) {
// R-1's NEGATIVE CONTROL ARM, and the only thing it turns off is the barrier. A
// reply-slot row still waits: the answer is not derivable here and R-5 forbids
// inventing one, so MOBILEGL_IPC_VERB_BARRIER=0 makes the queue free-running, not
// the client clairvoyant.
return seq;
}
const BarrierWaitScope waiting;
const Uint64 waitBudgetMs = AppliedWaitBudgetMs(op, payload);
const Transport::SessionWait wait =
WaitForAppliedBudget(m_producer, m_events, seq, waitBudgetMs);
if (wait == Transport::SessionWait::ShutDown) {
// `dl`: SHUTDOWN IS TWO DIFFERENT EVENTS AND ONLY ONE IS A DEVICE LOSS. Stop() kills
// this same bell to wake a parked applier, so an orderly exit arrives here too - and
// latching on Dead() alone would arm the device-lost flag on every clean teardown.
// PeerHungUp() is true only when a descriptor whose far end ONLY THE SERVER held
// reported hangup, which nothing this side can cause.
if (const Transport::Doorbell* bell = m_producer.SelfDoorbell();
bell != nullptr && bell->PeerHungUp()) {
LatchDeviceLost("the barrier woke on a peer that had hung up");
}
// The doorbell died: the server went away. The only thing that returns from a
// kWaitForever park, and therefore the only way a client blocked in the barrier
// survives a server that is gone. It is teardown, not a server fault - so the answer
// handed back is DECLINED, not the ERROR the status was pre-set to (M4): a
// reply-owning row that saw ERROR here would abort Fatal{ReplyError} on a shutting-
// down session, which is what the "teardown legitimately reaches here" comment
// promised would NOT happen. DECLINED is honest - "the verb did not happen" - and the
// acceptance rows already treat it as `false` / nullptr without aborting.
// ReadPixels intentionally refuses this with Fatal{ReadbackDeclined, "ReadPixels"}:
// unlike acceptance rows it cannot return successfully without complete pixels.
if (statusOut != nullptr) *statusOut = Wire::ReplySink::kStatusDeclined;
MGLOG_E("MG_Remote client: the barrier for %s (seq %llu) woke on a dead doorbell; the "
"server is gone and this verb did not happen (reported as DECLINED, not ERROR)",
Wire::WireOpName(op), static_cast<unsigned long long>(seq));
return seq;
}
if (wait != Transport::SessionWait::Reached) {
SessionFail(MGFatalFamily::BarrierTimeout, "MGPipe: Fatal{BarrierTimeout, \"%s\"} - appliedSeq did not reach %llu within "
"%llu ms. A bounded wait is deliberate: a wedged CI job and a lost record look "
"identical from outside, and only one of them is a bug worth finding",
Wire::WireOpName(op), static_cast<unsigned long long>(seq),
static_cast<unsigned long long>(waitBudgetMs));
}
// THE REVERSE CHANNEL IS DRAINED HERE, and here is the only place it can be: under the
// barrier this is the one instant at which the apply thread is known not to be inside
// the applier, and MGPipeClientOnGpuWritten / OnBufferWriteback write frontend objects.
// It is what gives AwaitBufferWriteback something to have waited FOR: b1's third state
// clears when the writeback lands, and the writeback lands on this ring.
DrainEventRing(m_events);
if (!ownsReplySlot) {
// P5e (ra, §2.3). A barriered record's apply has returned and this thread is the
// only runnable one, so the four O-class SharedPtr rows the last fill left in
// gPipeInputs can go. Under lockstep they were harmless - the next verb's fill
// overwrote them - but under run-ahead the next fill may be a frame away, and a
// frontend VAO or program whose LAST owner is that block is one the apply thread
// can end up destroying (§2.7's deferred-destroy hazard). Released here rather
// than at the fill, because here is where the applier is provably idle.
if (RunAheadArmed()) ReleaseFillPins();
return seq;
}
// THE SAME WAIT, NOT A SECOND ONE. appliedSeq >= seq already means the server wrote
// this record's answer, because it writes the slot before it advances the watermark.
Uint64 replySize = 0;
Int32 status = Wire::ReplySink::kStatusError;
if (!ReadReply(seq, replyOut, replyBytes, &status, &replySize)) {
SessionFail(MGFatalFamily::ReplyMissing, "MGPipe: Fatal{ReplyMissing, \"%s\"} - seq %llu carries kReplySlot and the "
"server applied it, but its slot does not stamp that seq. The stamp is what "
"makes a wrong-slot read detectable rather than plausible (R-3)",
Wire::WireOpName(op), static_cast<unsigned long long>(seq));
}
if (statusOut != nullptr) *statusOut = status;
if (replySizeOut != nullptr) *replySizeOut = replySize;
if (status == Wire::ReplySink::kStatusError) {
MGLOG_E("MG_Remote client: %s (seq %llu) answered ERROR", Wire::WireOpName(op),
static_cast<unsigned long long>(seq));
}
// DECLINED is NOT an error and is deliberately not logged as one: it is how
// MapPersistent says nullptr (R-6) and how the four Bool acceptance rows say false
// (R-5). A client that treated it as a failure would re-create ID-39 from the other
// side.
if (replyOut != nullptr && replySize > replyBytes) {
SessionFail(MGFatalFamily::ReplyTooLarge, "MGPipe: Fatal{ReplyTooLarge, \"%s\"} - the answer is %llu bytes and the "
"caller offered %llu. P5 does not chunk a reply",
Wire::WireOpName(op), static_cast<unsigned long long>(replySize),
static_cast<unsigned long long>(replyBytes));
}
return seq;
}
Bool ClientSession::BarrierArmed() const { return m_barrierArmed; }
// ---- P5e (ra): the run-ahead latch and the waits it leaves behind ---------------------
Bool ClientSession::RunAheadArmed() const { return m_runAheadArmed; }
// THE PRODUCER'S NUMBER, NOT A SECOND ONE. SessionProducer records it inside
// PublishAndNotify, which is the only place a record becomes published at all; a copy kept
// here would be a second thing to forget to write on a path that publishes without waiting
// - which, after P5e, is most of them.
Uint64 ClientSession::LastPublishedSeq() const { return m_producer.LastPublishedSeq(); }
Uint64 ClientSession::PresentCreditWaits() const { return m_presentCreditWaits; }
void ClientSession::LatchRunAheadFromCaps() {
#if MOBILEGL_BUILD_DISAGGREGATED
// THE CONJUNCTION, IN THE CONTRACT'S OWN ORDER (§1). The caps read is last because it
// is the only one that costs a mirror load, and because it is the only one whose answer
// can change: the other two are process configuration.
const Bool armed = m_barrierArmed && MG_Config::Ipc.RunAhead != 0 &&
Caps().HasCap(MG_Pipe::kCapRunAheadApply);
if (!m_runAheadLatched) {
m_runAheadLatched = true;
m_runAheadArmed = armed;
if (armed) {
MGLOG_I("MG_Remote client: run-ahead ARMED - the server publishes "
"kCapRunAheadApply, so an unbarriered record is published and not "
"waited for (CONTRACT-P5E §2.3), paced by a present credit of %u",
MG_Config::Ipc.PresentCredit);
} else if (MG_Config::Ipc.RunAhead != 0 && m_barrierArmed) {
// THE KNOB IS NOT A SWITCH ON ITS OWN, and an operator who set it has to be
// told that, or an A/B arm that measured nothing looks like an A/B arm that
// measured no difference (Config.h's own argument for parsing it everywhere).
MGLOG_W_ONCE("MG_Remote client: run-ahead requested, server does not publish "
"kCapRunAheadApply - running lockstep. The selected backend has "
"not enabled its implementation-readiness gate");
}
return;
}
// A LATER SNAPSHOT MAY ONLY TURN IT OFF. Promotion would mean the records already
// published without a wait were published against a rule this server never agreed to,
// and nothing can un-publish them; demotion only adds waits, so it is safe and is
// exactly what a server that lost its run-ahead backend needs.
if (!armed && m_runAheadArmed) {
m_runAheadArmed = false;
MGLOG_W("MG_Remote client: run-ahead DISARMED by a later caps snapshot - every "
"record from here waits as it did before P5e");
}
#endif
}
void ClientSession::ReleaseFillPins() {
#if MOBILEGL_BUILD_DISAGGREGATED
// The block's own door: PipeInputs' O-class rows are private and MG_Remote has no
// business knowing which four they are. MG_Impl owns the fill, so MG_Impl owns the
// un-fill (PipeFill.cpp), and this side only says WHEN.
MG_Pipe::MGPipeReleaseResidualFillPins();
#endif
}
void ClientSession::WaitForApplyToCatchUp(const char* why) {
#if MOBILEGL_BUILD_DISAGGREGATED
// A NO-OP WITHOUT RUN-AHEAD, and that is not an optimisation: under lockstep the
// client already waited for every record it published, so appliedSeq is at
// LastPublishedSeq by construction and a second wait would only add a park on a
// watermark that is already reached.
if (!m_runAheadArmed || !m_started) return;
const Uint64 target = m_producer.LastPublishedSeq();
if (target == 0) return;
const BarrierWaitScope waiting;
const Transport::SessionWait wait =
WaitForAppliedBudget(m_producer, m_events, target, kBarrierTimeoutMs);
if (wait == Transport::SessionWait::ShutDown) {
// `dl`: the same two-events distinction the verb barrier makes. Only a peer that
// HUNG UP is a device loss; Stop() reaches this path too.
if (const Transport::Doorbell* bell = m_producer.SelfDoorbell();
bell != nullptr && bell->PeerHungUp()) {
LatchDeviceLost("a forced run-ahead wait woke on a peer that had hung up");
}
// The doorbell died: teardown, not a fault - the same answer EmitAndWaitTails
// gives, and for the same reason.
MGLOG_E("MG_Remote client: the forced wait for %s woke on a dead doorbell; the "
"server is gone", why);
return;
}
if (wait != Transport::SessionWait::Reached) {
SessionFail(MGFatalFamily::BarrierTimeout, "MGPipe: Fatal{BarrierTimeout, \"%s\"} - a forced run-ahead wait did not "
"reach appliedSeq %llu within %u ms. The forced waits of CONTRACT-P5E §2.5 "
"are the points at which the client must be in step again, so a wedge here "
"is a wedge in the queue and not a slow frame",
why, static_cast<unsigned long long>(target), kBarrierTimeoutMs);
}
// EVERY WAIT EXIT DRAINS (§2.6). It is what the flow-control deadlock argument rests
// on: the server blocks only on a full event ring, the client blocks only on
// watermarks the server advances, and every client wait drains - so at most one side
// is parked at any instant.
DrainEventRing(m_events);
ReleaseFillPins();
#else
(void)why;
#endif
}
void ClientSession::Finish() {
// glFinish. Nothing goes on the wire - Flush and Finish have no record (ARCHITECTURE
// §11) - and under lockstep there was nothing to do, because the client had already
// waited out every command it issued. Under run-ahead "the commands issued so far have
// completed" is a promise the queue can break, so this is where it is kept.
WaitForApplyToCatchUp("glFinish");
}
Uint64 ClientSession::AcquirePresentCredit() {
#if MOBILEGL_BUILD_DISAGGREGATED
// MINTED CLIENT-SIDE AND 1-BASED (§1). Before P5e the client sent 0 and the server
// stamped its own frame count, which was honest while nothing paced on it; a credit
// needs an id space only the payer can advance, and that is this one.
const Uint64 serial = m_presentsSent + 1;
if (!m_runAheadArmed) {
// Lockstep: the present record's own barrier IS the pacing, one frame deep by
// construction. The serial is still minted so that both arms carry the same field
// and the server's ReturnPresentCredit is fed on both - an A/B whose two arms
// disagree about a wire field is not an A/B (Config.h's rule for the knobs).
m_presentsSent = serial;
return serial;
}
const Uint32 credit = MG_Config::Ipc.PresentCredit;
if (m_presentsSent >= credit) {
// Wait for swap number (serial - credit) to have come back. With credit 1 that is
// the previous frame: the client publishes frame N+1's records while the server
// applies and swaps frame N, and blocks here until swap N returned - one frame of
// overlap and at most one frame of added latency (ruling 4 / ID-92).
const Uint64 awaited = serial - credit;
++m_presentCreditWaits;
const BarrierWaitScope waiting;
Transport::SessionWait wait = Transport::SessionWait::TimedOut;
for (;;) {
// §2.6 again: the credit park breaks on a full SEG_EVENT too, for the same
// reason the applied park does - a server that stopped producing stopped
// swapping, and this waiter holds the only drain.
wait = m_producer.WaitForPresentAckOrEventBacklog(awaited, kBarrierTimeoutMs);
if (wait != Transport::SessionWait::Reached) break;
Transport::RingControl* control = m_producer.Control();
if (control == nullptr ||
Transport::Watermark::Reached(control->Progress.presentAckSerial, awaited)) {
break;
}
DrainEventRing(m_events);
}
if (wait == Transport::SessionWait::TimedOut) {
SessionFail(MGFatalFamily::PresentCreditTimeout, "MGPipe: Fatal{PresentCreditTimeout} - present %llu waited %u ms for "
"swap %llu to come back with a credit of %u. The credit, never the "
"ring's bytes, is what paces a run-ahead client (CONTRACT-P5E §2.4), "
"so a credit that never returns is a server that stopped swapping",
static_cast<unsigned long long>(serial), kBarrierTimeoutMs,
static_cast<unsigned long long>(awaited), credit);
}
// ShutDown is teardown and returns: the present did not happen, the same answer
// the barrier gives on a dead doorbell.
if (wait == Transport::SessionWait::Reached) DrainEventRing(m_events);
}
m_presentsSent = serial;
return serial;
#else
return ++m_presentsSent;
#endif
}
// R-1's mutual-exclusion invariant, as two probes that answer honestly.
//
// THE CLIENT'S FLAG IS THREAD-LOCAL AND THE SERVER'S IS NOT, and the asymmetry is the
// point: "am I inside a barrier wait" is a question about the calling thread, while "is the
// apply thread inside the applier" is a question the GL thread asks about a DIFFERENT
// thread in the shared-block control. Under role split each thread instead observes only
// its own diagnostic; the client writes a different block and waits through appliedSeq.
Bool ClientSession::InBarrierWait() { return g_inBarrierWait; }
Bool ClientSession::ApplyThreadIsInsideApplier() {
if (MG_Pipe::MGPipeRoleSplitRehearsalActive()) return g_roleInsideApplier;
return g_applyThreadInsideApplier.load(std::memory_order_acquire);
}
void ClientSession::RefusePipeInputsTouchWhileApplierOwnsIt(const char* surface,
Bool isBarrieredFill) {
// THE CHAIN IS A CONJUNCTION, SO ITS ORDER IS FREE - AND IT IS ORDERED CHEAPEST-FIRST
// (P5d round 3, package D). Every line below is a pure predicate whose only effect is
// "no violation, go home"; the Fatal fires on the AND of all of them, so reordering
// cannot change which touches abort. It changes only what a touch that does NOT abort
// pays, and this guard sits on the per-verb fill path (PipeFill.cpp:542, :1951, :2789
// - MGPipeValidateForVerb is 4.11% self / 10.9% inclusive of the client thread), so
// "what it costs to answer no" is the whole of its cost in a healthy process.
//
// The two config reads come first because they are the two answers that are constant
// for the life of the process and true for nearly every process that runs this code:
// a monolith build never has a role split at all, and MOBILEGL_IPC_BATCH_WAITS
// defaults to 1, which retires this guard by design (see its note below). Only after
// both miss do we pay for a role probe, two singleton reads, a shared atomic and the
// thread_local at the end.
if (MG_Config::Transport == MG_Config::TransportMode::Monolith) return;
// ---- P5e (ra), CONTRACT-P5E §3.5: THE RUN-AHEAD RULE IS A DIFFERENT RULE -----------
//
// It is first, before the BatchWaits return, because BatchWaits' argument does not
// survive run-ahead: "the pull-verbs' own wait keeps their pulled reads fenced" is a
// statement about a client that waits at every verb, and this one does not. Under
// run-ahead the block is SERVER-ROLE memory (§3) and the single legal GL-thread write
// is the residual fill of a BARRIERED record - the one the client is about to park
// behind. Every other touch races the applier by construction, so there is no
// in-applier flag to consult and no "count it" arm: the value would be torn.
//
// This is where a fill left standing for an unbarriered record lands, by name.
if (ClientSessionInstance().RunAheadArmed()) {
// ---- P5e (ra2): THE EXEMPTION IS A FACT NOW, NOT A CLAIM ------------------------
//
// This arm used to read `if (isBarrieredFill) return;`, i.e. the caller's own
// sentence "this touch is the residual fill of a record this thread is about to park
// behind" was accepted as the whole argument. It is an argument about the FUTURE.
// The order at the validate point is fill, then emit, then park, so at the instant
// of the write the apply thread is still draining the unbarriered records the client
// ran ahead of - and the measured consequence was the GL thread bumping
// CurrentVerbSerial, withdrawing MGPipeServerClearVerbBoundary's flag and renaming
// m_currentVerb underneath a record the applier was inside, which surfaced as
// Fatal{UnmigratedPipeInput, "<field>@<the client's verb>"} on the apply thread.
// Because the exemption was unconditional, this guard could not fire on any of it:
// that is the answer to "does RefusePipeInputsTouchWhileApplierOwnsIt fire, and if
// not, why not".
//
// So the sentence still exempts the fill, but only once it is TRUE of this instant.
// The fill sites establish it by taking §2.5's forced wait first
// (QuiesceApplierBeforeFill, PipeFill.cpp); removing that wait is the red-once and
// lands here, by name, on the first barriered verb behind a run-ahead backlog.
//
// ApplyThreadIsInsideApplier() is an acquire load of the flag PipeApplier raises for
// the whole of ApplyOne - stamp, decode and LeaveApplier included - so "not inside"
// is exactly "no record is being applied" and not merely "not decoding".
if (isBarrieredFill && !ApplyThreadIsInsideApplier()) return;
if (Server::ServerLoop::OnApplyThread()) return; // the applier owns the block
SessionFail(MGFatalFamily::RoleViolation, "MGPipe: Fatal{RoleViolation, \"gPipeInputs\"} - the GL thread touched "
"gPipeInputs (%s) on a RUN-AHEAD session %s. With the client running ahead "
"the block is the server's to read for as long as ANY record is in flight "
"(CONTRACT-P5E §3), so the only legal GL-thread write is a barriered fill "
"that has first taken §2.5's forced wait (QuiesceApplierBeforeFill)",
surface,
isBarrieredFill ? "in a barriered fill that did not first wait for the "
"applier to catch up"
: "outside a barriered fill");
}
// MOBILEGL_IPC_BATCH_WAITS=1 makes "the fill runs while the apply thread applies an
// earlier value record" the INTENDED shape: the fill writes only fields no record
// supplies (the wire-live skips are the same answer the emitters use), the applier
// writes only record-supplied fields, and the pull-verbs' own wait keeps their
// pulled reads fenced. This guard exists for the model where that is not true, so
// it stands only while the batch is off.
if (MG_Config::Ipc.BatchWaits != 0) return;
if (Server::ServerLoop::OnApplyThread()) return; // the applier owns the block inside a verb
if (!ClientSessionInstance().Started()) return; // the bring-up window pre-dates the roles
// MOBILEGL_IPC_VERB_BARRIER=0 is R-1's NEGATIVE CONTROL: the single-writer rule is off
// by the operator's own hand there, and EmitAndWait's Fatal{BarrierViolation} owns the
// red. Firing here instead would pre-empt the control's evidence line.
if (!ClientSessionInstance().BarrierArmed()) return;
if (!ApplyThreadIsInsideApplier()) return;
// LAST, because it is the only thread_local left in the chain: an emutls call per
// access in a shared library, and it must stay thread-local (see InBarrierWait's note
// above - a second GL thread would otherwise read the first one's wait as its own).
if (InBarrierWait()) return;
SessionFail(MGFatalFamily::RoleViolation, "MGPipe: Fatal{RoleViolation, \"gPipeInputs\"} - the GL thread touched gPipeInputs "
"(%s) while the apply thread was inside the applier and this thread was not in a "
"barrier wait. R-1's barrier is the only thing that makes one process-wide "
"gPipeInputs legal (CONTRACT-P5 table 3); a touch in this window races the "
"applier's own reads of it",
surface);
}
void ClientSession::NoteApplyThreadEnteredApplier() {
g_roleInsideApplier = true;
if (!MG_Pipe::MGPipeRoleSplitRehearsalActive())
g_applyThreadInsideApplier.store(true, std::memory_order_release);
}
void ClientSession::NoteApplyThreadLeftApplier() {
g_roleInsideApplier = false;
if (!MG_Pipe::MGPipeRoleSplitRehearsalActive())
g_applyThreadInsideApplier.store(false, std::memory_order_release);
}
Uint32 ClientSession::PumpControlPlane() {
// NOT gated on m_started. The first snapshot arrives DURING Start(), before this session
// is started or active - and s1's half-built teardown path depends on m_started staying
// false until step 8 has succeeded, so the flag cannot be moved earlier to suit this.
if (m_transport == nullptr) return 0;
Uint32 adopted = 0;
// Bounded rather than `while (true)`: a server that queued frames faster than this
// drains them would otherwise hold the GL thread here for ever, and a frame backlog
// deeper than this is a finding rather than a steady state.
for (Uint32 guard = 0; guard < kMaxControlFramesPerPump; ++guard) {
if (m_transport->PeekFrameSize() == 0) break;
std::vector<Uint8> frame;
if (ReceiveEnvelope(*m_transport, frame, 0) != MOBILEGL_OK) break;
const ::MobileGL::Wire::CtrlEnvelope* envelope = ParseEnvelope(frame);
if (envelope == nullptr) {
MGLOG_E("MG_Remote client: an unverifiable control frame (%llu bytes) was dropped",
static_cast<unsigned long long>(frame.size()));
continue;
}
if (envelope->msg_type() != ::MobileGL::Wire::CtrlMsg::CapsSnapshot) {
// SurfaceOp / SurfaceReply / ResyncRequest / AuxRequest / LogLine are P6's and
// P7's. Named rather than ignored, so a phase that starts sending one does not
// discover this loop swallowing it.
MGLOG_W("MG_Remote client: control message %d is not consumed in P5",
static_cast<int>(envelope->msg_type()));
continue;
}
if (AdoptCapsSnapshot(envelope->msg_as_CapsSnapshot())) ++adopted;
}
// P5e (ra, §1): the run-ahead latch rides R-12's invalidation edge, because "the first
// caps adoption after Start" and "the one place a CapsSnapshot becomes a mirror
// generation" are the same instant, and a latch taken anywhere else would be reading a
// mirror whose generation nobody had adopted yet. Called even when `adopted` is 0: the
// first call in Start() is what takes the latch, and a pump that adopted nothing still
// has to leave it taken (a handshake with no snapshot latches "not armed", which is
// the honest answer for a server that never said what it consumes).
if (adopted != 0 || !m_runAheadLatched) LatchRunAheadFromCaps();
return adopted;
}
Transport::SessionProducer& ClientSession::Producer() { return m_producer; }
Transport::SessionWait ClientSession::WaitForApplied(Uint64 seq, Uint32 timeoutMs) {
return m_producer.WaitForApplied(seq, timeoutMs);
}
Bool ClientSession::ReadReply(Uint64 seq, void* outBytes, Uint64 outCapacity, Int32* outStatus,
Uint64* outSize) {
return m_replies.Read(seq, outBytes, outCapacity, outStatus, outSize);
}
Uint32 ClientSession::MaxReplyBytes() const { return m_replies.MaxReplyBytes(); }
Bool ClientSession::ReplyCanHold(Uint64 bytes) const { return m_replies.CanHold(bytes); }
// ID-47. Forwarded verbatim so that the message, the boundary and the abort are the pool's
// and are pinned once, in SessionTest, rather than re-derived per caller.
void ClientSession::RequireReadPixelsReplyFits(Uint32 width, Uint32 height, Uint32 format,
Uint32 type, Uint64 bytes) const {
m_replies.RequireReadPixelsFits(width, height, format, type, bytes);
}
Transport::EventRingConsumer& ClientSession::Events() { return m_events; }
Uint32 ClientSession::DrainPublishedEvents() {
// Not gated on m_started on purpose: PumpControlPlane's own pre-start call during
// Start() has its ring-consumer twin here, and DrainEventRing's Valid() check is
// the whole guard either case needs.
return DrainEventRing(m_events);
}
Uint64 ClientSession::EventRingCapacityBytes() const { return m_shm.EventRingCapacity(); }
Uint64 ClientSession::StageCapacityBytes() const { return m_shm.StageBytes(); }
Wire::SegmentTable& ClientSession::Segments() { return m_segments; }
Transport::RingControl* ClientSession::Control() { return m_shm.CmdControl(); }
Transport::SessionSegments& ClientSession::Shm() { return m_shm; }
Transport::ITransport* ClientSession::Control_Plane() { return m_transport; }
Transport::RoleMemorySample ClientSession::SampleMemory() const {
return Transport::SampleRoleMemory(Transport::MemoryRole::Client);
}
void ClientSession::LogMemory(const char* phase) const {
Transport::LogRoleMemory(phase, SampleMemory());
}
// R-10's AND R-9's numbers IN EVERY SPLIT PRIVATE LOG, not only in the lanes that set
// MOBILEGL_PIPE_STATS=1.
//
// WHY IT IS HERE AND NOT ONLY ON THE STATS LINE. `MGPipe stats:` is an opt-in channel: two
// ctest entries out of 21 set MOBILEGL_PIPE_STATS, and neither the retrace lanes nor the
// 19 ordinary split entries do. R-10's proof obligation is about THE PHASE, not about the
// two counting lanes - "no record on the reduced path comes near half the ring" has to be
// readable from any split run that happened, which is what ID-53's per-entry private log
// is for. One line per session teardown costs nothing and cannot be missed.
//
// IT IS ALSO WHERE THE PROOF FAILS SOFTLY. A record ABOVE the cap already aborts on the
// spot with Fatal{RingOverrun} (PipeWireCodec.cpp), so this line's job is the other half:
// a maximum that is merely CLOSE to the cap is not a crash and would otherwise be
// invisible until the day a workload crossed it. The percentage is printed for exactly
// that reason, and R-10 names the integrator as the person who decides between early
// chunking and a bigger default ring when it climbs.
void ClientSession::LogWireLedger() const {
const Uint64 maxRecord = m_encoder.MaxRecordBytesSeen();
const Uint64 cap = m_encoder.MaxRecordBytesCap();
// Integer permille rather than a float: this file has no <iomanip> and a "%.1f" of a
// ratio nobody can reproduce by hand is worse than two integers.
const Uint64 permille = cap != 0 ? (maxRecord * 1000ull) / cap : 0ull;
MGLOG_I("MG_Remote client: wire ledger: maxrec=%llu maxrecop=%s cap=%llu (%llu.%llu%% of "
"RingProducer::MaxRecordBytes, half of a %llu byte SEG_CMD) cmdbytes=%llu "
"ringwraps=%llu ringpads=%llu "
"ringwaits=%llu emitseq=%llu cliwait=%llu clipark=%llu credit-waits=%llu - "
"R-10's proof obligation, R-9's producer readings, P5d round 3's client wait "
"pair and P5e's present credit, published from the session that produced them",
static_cast<unsigned long long>(maxRecord), m_encoder.MaxRecordOpName(),
static_cast<unsigned long long>(cap),
static_cast<unsigned long long>(permille / 10),
static_cast<unsigned long long>(permille % 10),
static_cast<unsigned long long>(cap * 2),
static_cast<unsigned long long>(m_encoder.CmdBytesWritten()),
static_cast<unsigned long long>(m_encoder.CmdWraps()),
static_cast<unsigned long long>(m_encoder.CmdWrapPads()),
static_cast<unsigned long long>(m_encoder.StageReclaimWaits()),
static_cast<unsigned long long>(m_encoder.EmitSeq()),
// The same pair the summary line's wait[] carries, on the channel that exists
// in EVERY split private log rather than in the two counting lanes: the round-3
// profile runs did not set MOBILEGL_PIPE_STATS either, and "did the barrier spin
// or did it park" is the question their logs have to be able to answer.
static_cast<unsigned long long>(m_producer.Waits()),
static_cast<unsigned long long>(m_producer.Parks()),
// P5e (ra, §2.4). The number the device exit reads to say whether the present
// credit is what paces this workload: 0 with credit 1 means the server is
// never the frame's critical path, and a count near the frame count means it
// always is. It is on this line rather than only on the stats line for
// LogWireLedger's own reason - a trace replay never reaches a stats summary.
static_cast<unsigned long long>(m_presentCreditWaits));
}
#undef MGP5_C0_STUB
} // namespace MobileGL::MG_Remote::Client
Reference in New Issue View Git Blame Copy Permalink