swung0x48 8b68b92c76 [Docs] (Disaggregated): P5f section 1 - the pointer fact, and one draw's full lifecycle through gPipeInputs ...

The section explained what gPipeInputs IS and what breaks under spawn, but not the one fact
that decides the shape of the fix, and not how a call actually reaches the driver through it.
Both are now in the document rather than only in the conversation that found them.

- THE POINTER FACT, now stated first because everything else follows from it: several
  BARRIER_PULLED fields do not hold values, they hold pointers into client-owned objects.
  PipeFill.cpp:274 fills m_textureUnitBase with `&ctx.GetTextureUnitObject(0)` - a raw base
  into the frontend's array - and :245 fills m_programForDraw with a SharedPtr<ProgramObject>.
  PipeInputs.h:669 dereferences it as `m_textureUnitBase[unit]`. PipeFill.cpp:2591-2592 says
  the same of the shader-buffer field: "four raw bases into the frontend's binding-point
  table".
  The consequence gets its own paragraph in 1.4, because it is the step most likely to be got
  wrong: this CANNOT be fixed by moving the block into shared memory. Mapping the same pages
  into both processes does not make a client heap address meaningful in the server, and a
  SharedPtr's refcount does not cross at all. The 15 fields each need a different SOURCE, not
  a shared location.

- NEW 1.2, one draw end to end: glBindTexture marks a tracker bit and sends nothing, because
  push only happens at a verb boundary; glDrawArrays enters MGPipeValidateForVerb
  (PipeFill.cpp:3347) whose four steps are barrier decision, dirty walk, emission (records,
  carrying handles), and the residual fill - which is where BARRIER_PULLED happens; the record
  goes on SEG_CMD; the apply thread dispatches to the backend; PrepareForDraw reads either a
  record-carried handle against the server's own tables, or gPipeInputs; then the real driver
  call. Plus the field lifetime: stamped with verb N's serial, read during verb N's apply,
  Fatal{UnmigratedPipeInput} if read at verb N+1 without a refill - one verb, never longer.

- The same example carries the Espryt/Magma split concretely: the texture binding reaches
  Espryt as a record with a handle (P5e retired GetTextureUnitObject for it) and reaches Magma
  through gPipeInputs into the client's array. That is FieldOwnership.def's own
  "P5e (Espryt unbarriered), P7 (Magma)" made legible, and it is why section 2.1's table has
  eight rows in that state.

Sections renumbered 1.1-1.4. Doc citation lint: 129 citations, 0 problems.

2026-09-19 06:02:28 -04:00

..

Disaggregated

[Docs] (Disaggregated): P5f section 1 - the pointer fact, and one draw's full lifecycle through gPipeInputs

2026-09-19 06:02:28 -04:00