Ticket 6: execution/event model (ADR 0006) — design for ticket 8 - #179
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Ticket 6: execution/event model (ADR 0006) — design for ticket 8#179SnowCheetos wants to merge 1 commit into
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Nonblocking poll_event via vkGetFenceStatus (no worker thread); bounded (CB, fence, descriptor) ring per context sized at max_events_per_context; Timeout::AfterNs rejected pre-admission (Hexagon/XDNA precedent); DEVICE_LOST -> Failed(DeviceLost) plus sticky poisoned instance; no EVENT_CANCELLATION.
This was referenced Sep 3, 2026
SnowCheetos
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September 3, 2026 08:39
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🟡 Changes recommended
The new ADR contains a verified misquote/inconsistency with SAFETY.md and a small spelling/formatting issue that should be corrected to keep design documentation accurate.
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Pull request overview
Adds ADR 0006 documenting the Vulkan backend’s execution/event model decisions needed to unblock the ticket 8 implementation work, with emphasis on nonblocking fence polling, bounded resource pools per context, and explicit timeout/cancellation semantics.
Changes:
- Introduces ADR 0006 describing
poll_eventviavkGetFenceStatus(no worker thread) and a bounded ring of (CB, fence, descriptor) resources per context. - Defines the submission “admission boundary” at
vkQueueSubmitsuccess, and rejects finiteTimeout::AfterNspre-admission withBackendError::DeadlineExpired. - Specifies device-loss mapping (sticky instance poisoning) and explicitly does not advertise
EVENT_CANCELLATION.
File summaries
| File | Description |
|---|---|
| docs/adr/0006-execution-event-model.md | New ADR capturing the execution/event model and constraints for the Vulkan backend ahead of ticket 8. |
Review details
Suppressed comments (1)
docs/adr/0006-execution-event-model.md:43
- “re-factoring” should be “refactoring”, and the current line break splits “under lavapipe” awkwardly; rewrap this paragraph for readability.
If ticket 8 benchmarks show `vkGetFenceStatus` polling dominates steady-state (e.g. under
lavapipe), the fallback to a worker-thread poll sits behind the same slot ring unchanged; the
AST gate in ticket 8 measures before re-factoring.
- Files reviewed: 1/1 changed files
- Comments generated: 1
- Review effort level: Lite
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| backends, no dispatch/synchronization worker is serialized. Ticket 8 proves this — the clause | ||
| in SAFETY.md says "no worker thread (proven in ticket 6, not assumed)" in proof form: if ticket | ||
| 8's I/O reaches indeterminate under blocking-poll, this design reopens. |
This was referenced Sep 3, 2026
SnowCheetos
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area: backend
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Stacked on #177. Resolves map ticket 6 (grilling). Decisions: nonblocking poll_event via vkGetFenceStatus (no worker thread; ticket 8 proves it); bounded (CB, fence, descriptor) ring per context sized at max_events_per_context; vkQueueSubmit success the admission boundary; Timeout::AfterNs rejected pre-admission with DeadlineExpired (Hexagon/XDNA precedent) since Vulkan lacks cancel; DEVICE_LOST maps to Failed(DeviceLost) + sticky instance poisoning; EVENT_CANCELLATION never advertised. Falsification guard: if fence polling dominates steady-state on lavapipe, a worker-thread poll sits behind the same slot ring unchanged.