The last piece of state ownership this phase owed: the eight DirectGLES twin
tables resolved a handle process-wide, so two contexts of one session that do
NOT share a share group - which have independent name spaces, so the same
{slot, gen} in both is legal - were handed the SAME twin, driver ids,
persistent map and pooled store included. Two contexts that DO share a group
were served by whichever of them twinned first. Design and per-slice shape:
docs/Disaggregated/design/11-state-ownership.md (S6).
Key: DirectGLES.h's TwinKey{SessionKey, ShareGroupKey} - the same two words
the applier's object records are filed under, with the group derived by
MGPipeApplierShareGroupKeyFor so a record and the twin describing it can never
land in different buckets. Session is in the key because a twin names a driver
id and no driver id crosses a connection.
Resolution: SessionRuntime.cpp's ResolveThreadTwinKey, installed by
InstallSessionRuntimeHooks beside the S2 PipeInputs probe, the S4 native
tuple key and the S5 applier key. It reads the ThreadSessionScope's session
and CurrentContextToken() - apply-thread state only, never MG_State, so the
frontend-keyed-lookup prohibition on the apply thread still holds. A thread
that belongs to no session answers {0, 0}, which is the process singleton this
replaces; the monolith and every unit case are unchanged by construction.
Shape: SlotTables.h's SlotTableRegistry holds one SharedPtr bucket per key,
with a thread-local last-key memo. It forwards every handle-keyed entry -
GetOrCreate, FindByHandle, LiveGenAt, HandleOf, StateForHandle,
NoteStateForHandle, ReleaseByHandle, ForEachLive, the counters - to the
CALLING THREAD's bucket, so the ~150 call sites in Managers.cpp and
DirectGLES.cpp are literally unchanged. The holder list stays process-wide: a
death notice is about an object, not a bucket, and each shared holder is one
bucket. ForEachLive now walks the calling thread's bucket (what a context can
see is its own group); the death and diagnostic walks take the new
ForEachBucket.
DropEveryTwinForEndedServerSession is session-scoped: it runs on the apply
thread of the session that is ending, while S2 lets neighbour sessions keep
rendering in the same process. No session on the thread keeps the old
process-wide drop verbatim. Managers.h's "a texture is owned by exactly one
context (share groups are not implemented)" is corrected: a texture belongs to
a share group and its sibling contexts legitimately mutate it.
Tests: MG_Test/Wire/TwinOwnershipTest.cpp, five cases driving the real twin
tables with no EGL and no wire - the same handle in two nonshared groups is
two twins and neither overwrites the other; two contexts of one group resolve
ONE twin; a per-session drop takes only that session's; a thread with no
session still gets the process-wide table; and the six-registry template
repeats the first three. Negative control run and reverted: making the
registry answer a single {0, 0} bucket turns four of the five red.
Full host ctest against a stashed baseline, compared by test name: 0 new
failures. The one name in the difference set
(LogForwardChannel.APeerThatStopsReadingCostsWarnLinesNotTheCallersTime) is a
pre-existing flake, failing on the baseline too with the identical assertion.
The 103-case acceptance set plus the five new cases is 108/108 green.
Remaining debts (documented): the unit shadows (g_activeTextureUnit,
g_boundTexturesCache, g_boundSamplersCache) are still process-global; the
driver-level glIsBuffer probe is still not usable on this host, so sharing is
proven at the twin layer (the twin IS the object holding the driver id); the
backend context/sync generations are still process-wide; the per-record
ContextSlot is still S1's edge declaration.
Breaks the one process = one server = one session = one context equation
that the whole stack's correctness used to rest on. Design and per-slice
shape: docs/Disaggregated/design/11-state-ownership.md.
S1 wire: bind_context ring record (opcode 84) announces the current
context at the make-current edge; CreateContext/DestroyContext join the
SurfaceOp control frames; control revision 5 -> 6; the server keeps a
per-session token table and refuses unknown tokens by name.
S2 server: SessionRuntime per session with thread-scoped resolution
(singletons become fallbacks), per-thread gPipeInputs, per-session latch
domains, per-thread segment resolvers; the in-process unix supervisor
serves up to MOBILEGL_IPC_INPROC_MAX_SESSIONS (16) concurrent sessions;
surface mode is declared per session and the display lease refuses a
second on-screen session by name.
S3 frontend: ShareGroupState owns the shared object stores and name
generators (buffer/texture/renderbuffer/sampler/program), GLContext keeps
per-context bindings/errors/container objects; pGLContext becomes
thread-local with a process default context preserving the single-context
world verbatim; eglCreateContext builds a real GLContext and joins the
sharing context's group.
S4 backend: native EGL tuples keyed by (session, context token);
InitDisplayAndContext's unconditional teardown is gone - creating a
second context or surface no longer destroys the first; eglCreateContext
sharing is wired to the native driver; bind_context is the native switch
point.
S5 applier: MGPipeApplierState splits into MGPipeObjectRecords (per
share group) and MGPipeWorkingState (per context), resolved through a
{session, token} registry with a thread-local cached fast path.
Tests: MultiSessionTest (incl. two sessions x two contexts interleaved
with real clear/readback witnesses), ApplierOwnershipTest (with a
null-resolver negative control), ContextStateOwnershipTest,
ServerLoopEglTest native-context liveness; 99/99 of the acceptance set
green on the host build.
Known debts (documented in the design doc): twin registries still keyed
by handle alone, no per-record ContextSlot, process-global backend
generations, MakeCurrent dedup per current binding.
Five deaths in the split server image raised their own std::abort(). Three of them are
funnels - MagmaWireFatal (Renderer/WireFramebuffer.inc), WireDescriptorFatal
(Renderer/UniformManager.cpp) and WireBufferLegacyFatal (Renderer/WireDraw.inc) - and the
fifteen `@P7` refusals on the tree (8 in UniformManager.cpp, 4 in WireFramebuffer.inc, 2 in
WireDraw.inc, 1 in VulkanRenderer.cpp; plan section 1.3's count confirmed) all die through
two of them. Every one of those deaths published NO SessionFault frame, so the peer read a
bare EOF; bumped NO SessionFaultCount(), so exit gate S8 could neither confirm nor falsify
it; and carried a hand-typed family word with no path to FatalFamilies.def's projection.
MG_Backend may not name an MG_Remote symbol on its own account, so the route is a seam in
MG_Pipe with MGP_TRIP_WIRE_REPORT's shape (PipeApply.cpp:66, and the new code sits beside
it): MG_Pipe/PipeSessionFail.h declares MGPipeSessionFail, PipeApply.cpp defines it inside
`#if MOBILEGL_BUILD_DISAGGREGATED`, the DEFAULT behaviour is byte-identical to what the
three funnels did on their own, and MG_Remote::InstallPipeSessionFailHook() points it at
SessionFail. The install is in InitServerRoleCommon (MG_Backend/Init.cpp), step 0, because
that is the one function BOTH server roles run - the inproc role and the spawn/TCP session
child - so there is no per-transport install to get wrong.
MGPipeFatalFamily is a two-value boundary enum, NOT MGFatalFamily cast to an integer: the
.def's enumerators are positional and a row inserted in its middle would silently re-point
every hook call at a different family. FatalFunnel.cpp's adapter is the one place the two
vocabularies meet, as a switch with a named default.
The family word stays UnmigratedVerb rather than becoming a new MagmaWireRefusal. Three
reasons: the message strings are required to stay byte-identical (5.2), and the retrace
refusal censuses recorded since P5b count these deaths by that word - a rename invalidates
every `@P7` measurement taken against them; `Magma:` in the detail already separates the
Magma arm from the GLES UnmigratedVerb deaths, so a new word adds no discrimination a grep
does not have; and its wire projection would be ProtocolCorruption, exactly UnmigratedVerb's.
Recorded for the integrator.
Ph slice (2) in the same commit: Server/StagedShadow.h's RequireCovered and
Server/StagedTextureStore.h's RequireLevelBytes were MGLOG_F + bare abort. Both are inside
MG_Remote already, so they call SessionFail directly, message verbatim;
check_include_closure.py's four probes do not reach either header and the gate is green.
Census: 83 abort sites -> 79 over 20 files (five sites retired, one gained for the seam's
no-hook default, which is argued into FUNNEL_SITES), baseline rewritten in this commit - the
downward ratchet's notice is what asked for it. Two gate bugs the widening exposed and this
commit fixes: the SessionFail call regex also matched `MGPipeSessionFail(` (a lookbehind
now), and a funnel's anchor needed a wider window than a marker's (kFunnelAnchorWindow).
Red-once, three ways. Pointing MagmaWireFatal back at its own abort reds the census naming
WireFramebuffer.inc 0 -> 1. Making the seam skip the hook reds both new death cases -
`TheMagmaWireVerbDeathReachesSessionFailAndBumpsTheFaultCount` on the exit code, because it
reads SessionFaultCount() out of a SIGABRT handler and gets 0 instead of 1, and
`TheSeamHandsTheInstalledHookItsFamilyAndItsLineVerbatim` on the line the hook echoed.
CONTRACT-P6 3.2 (D1c), 3.3 (D13) and 3.4 (D10).
Every guard below asked a question a SERVER PROCESS answers wrongly - "is a
ClientSession active" (never, there) or "am I on the apply thread" (every
thread is, there) - so all four were present, compiled, and permanently
disarmed in the one shape they exist for. That is worse than absent: it reads
as coverage.
D13 FIRST, THEN THE WIDENING. MGPipeRoleSplitActive() meant "the REHEARSAL
knob is on AND the transport is real", so widening it in place would have left
a narrow name describing a wide predicate. It is renamed to
MGPipeRoleSplitRehearsalActive() across its 12 sites - including the
DualBlockScenario assertion message that embeds it - and the wider predicate
is introduced BESIDE it.
MGPipeBlocksAreDistinct() IS TRUE FOR TWO DIFFERENT REASONS, which is the
whole point: under the rehearsal the two blocks are distinct objects in one
process; under SPAWN they are distinct because they are in different ADDRESS
SPACES, and no knob is involved. The spawn retrace runs with
role-split-state=0 - measured off the lane's own log - so every guard gated on
the rehearsal was off there.
THE CRASH. MGPipeServerBlockNoteIdentity early-returned on the rehearsal, so a
spawn server's gPipeInputs.ContextIdentity() stayed nullptr for the life of the
process. DirectGLES' framebuffer binding-slot memo compares that identity FIRST
and with NO generation, against a cache variable that also starts nullptr - so
nullptr == nullptr reads as a CACHE HIT and the function returns a slot pointer
nothing ever filled. `sm` widens the gate; `st` lands the named Fatal
PipeInputs.h had already asked for, so a reopening says which memo and which
identity instead of corrupting memory three frames later. Guarded on
MOBILEGL_PIPE_PUSH: in a pull build that identity is the live GLContext's
address and is never null, so the test would be dead code and G1 measures that.
DISJUNCTS, NOT SUBSTITUTIONS - and this was measured the hard way. The first
attempt REPLACED OnApplyThread() with MGPipeServerArm() and
ClientSession::Active() with MGPipeSessionLive(). 14 RemoteGuards and
RemoteClientControls cases went green by omission: a ServerLoop fixture with no
client session has only the original facts, so swapping them out disarmed every
test that drives the apply thread directly. The originals stay; the new
predicates are added beside them.
AND THE PROBE HAD TO BE THE RIGHT ONE. Installing
ClientSession::ApplyThreadIsInsideApplier as the apply-thread probe made every
GL-thread call a role violation whenever the applier happened to be busy - the
inproc retrace died on Fatal{RoleViolation, "MGPipeSlots"} raised from the GL
thread. "Am I the apply thread" and "is the apply thread inside the applier"
are different questions; the second is R-1's mutual-exclusion probe and is
about another thread entirely. ServerLoop::OnApplyThread is the one the guards
mean.
Three of D1c's six predicates land here, the three the four guards need. The
other three (MGPipeSplitActive, MGPipeShouldDial, MGPipeBackendIsLocal) have no
D10 site and are not added as dead code; their call sites are ContextEpoch and
ActiveXfbState, which this commit does not touch.
D14 holds: the non-disaggregated build gets constexpr false definitions, not
runtime-false predicates, so every consult folds at compile time. G1
re-measured - 0 symbol diff, .text unchanged at 0xa52203.
Two test names added, both falsifiable by construction: the spawn case asserts
the blocks are distinct with the rehearsal knob OFF, and the monolith case
asserts the predicate is not simply a constant. Unit suite 2353 tests, one
pre-existing environmental failure. All six OpenRA arms green.
ONE RECORD'S BLOB IS STAGED WHOLE IN SEG_STAGE, a linear arena, so a texture
level larger than the segment's chunk budget was Fatal{RingOverrun, "SEG_STAGE"}
at the encoder rather than a split - and the CI traces hit it: the texture half of
resource_subdata stages the whole level shadow regardless of how little of it
changed, and a 512x128x33 GL_RGBA32F level is 34,603,008 bytes while a 192-cube
GL_RGBA16 level is 56,623,104, both against the default 32 MiB segment. Three
retrace cases aborted there: iterationt-in-world and iterationt-nodsa-in-world in
both backends, and iterationrp-in-world in DirectVulkan.
THE CLIENT now cuts such a level into WHOLE-WIDTH SLABS, one resource_subdata
each (TextureEmit.h's MGPipeForEachTextureSlab, driven at MGPipeStageChunkBytes -
the same cap PipeFill.cpp's buffer walks are cut at). A piece is a set of
consecutive rows of the level shadow, so its box names both its texels and its
byte run; whole slices are the coarsest cut, a slice bigger than the cap falls
back to whole rows and a row bigger than the cap to whole texels inside one row.
Every piece is emitted, dirty or not: the server assembles one level image out of
the runs, so a piece left out would leave a hole no texel read can answer. Each
piece carries at least one region (its clipped dirty rects, or its own box when
none reaches it) because RegionCount == 0 remains the whole-level spelling, and
each region's SrcOffset is rebased onto its own piece's run - MGPipeTypes.h has
always said SrcOffset is "into the blob" - while the strides stay the level's. A
level that FITS keeps the single whole-level record, field for field what it has
always been, which is what every existing gate is written against.
THE SERVER now assembles levels from those runs. StagedTextureStore::AdoptRun
places one run at an image offset, its coverage set is exactly the runs it has
adopted (StagedShadowStore's CoverageAdd, the buffer half's helpers), and only a
FULLY covered level satisfies IsCovered / RequireLevelBytes - a level with one
piece missing is as unreadable as one that never arrived, and it is the same
Fatal{StageSnapshotTooNarrow}. The whole-level spelling survives as Adopt, its
offset-0 replacement, and the two are told apart by the run's own LENGTH: the
whole-level run is the level's complete shadow whatever its box says, a piece's
run is exactly its box's byte extent. Both adoption call sites -
Ops_H_TextureSubData and PipeApply.cpp's hookless fallback, which is what Magma
takes - read the offset that way.
THE PROTOCOL IS UNCHANGED: no field moved, no caps bit was added. The one
compatibility statement is that a split level now crosses as several records of
one apply batch, so an OLD server (which replaces the level on every record) would
keep only the last piece - inproc runs both roles out of one library, so the
constraint is noted here rather than armed with a gate.
Tests. TextureEmit.ALevelTooLargeForTheStageChunkIsCutIntoSlabs drives the split
at MGPipeStageChunkBytesFor's clamp with both trace shapes (5 and 7 slabs), the
row-granularity and texel-granularity fallbacks, the three shapes that refuse to
cut, the region clipping/rebasing, and the piece no rect reaches.
StagedTextureStoreTest gains the multi-run assembly, the gap that must not read as
coverage, the partial-level Fatal by name, the run-offset discriminator, and two
production cases - the applier's hookless arm and DirectGLES's real TextureSubData
hook - that would put both halves at the front of the image if the offset were
dropped.
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