 Markus Fritsche
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53e247724f
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iter6 v2 attempt-2 close — 0004 headless-clean but compositor-wedges
Step 2.1 (0004 vb2 helper alone) on lockdep+ramoops kernel:
- Headless smoke test PASS: ffmpeg rc=0, 4147200B output, zero
lockdep splat, iter4-DIAG validate_sps per-frame, iter5-IRQ DEC_RDY=1
- ~10 min later when GPU compositor + concurrent vb2 traffic active:
silent wedge → panic_timeout=10 → boot loop
- PROVE_LOCKING + 9 other lock-debug flags DID NOT catch it before wedge
Architect H1 hypothesis (classical lock-order inversion lockdep models)
is incomplete. Refined hypothesis ladder for v3:
- H1' cross-context wait not modeled by lockdep (KCSAN)
- H2 use-after-free / double-signal of dma_fence (KASAN)
- H3 race in fence alloc/init under concurrency (KCSAN)
- H4 panthor consumer-side bug (separate non-vb2 test)
Sub-bug fixed during execution: forcibly-rebuild-all-vb2-consumers
required after 0004 (touch core.h + make -j8 modules), otherwise
ABI mismatch produces 0-byte ffmpeg output.
DT-based ramoops reservation works (memmap= cmdline is x86-only).
Verified 2465B+70818B ramoops capture across panic+reset.
Recovery via WeChat stick chroot — 4 modules restored to pre-base
md5s, extlinux default flipped to arch_devices vanilla. Ampere
confirmed clean.
v3 plan pending: add KASAN+KCSAN+DEBUG_PREEMPT, full rebuild,
intentionally reproduce wedge under compositor. ~75 min build.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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2026-05-16 19:26:30 +00:00 |
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