[teo1747]

Implements CONFIG_EMB_TIME_SLICING, which existed in Kconfig without an implementation (KRN-SCH-007, KRN-SCH-026, KRN-SCH-037; SPEC-003 §8, KRN-TIM-029). The project owner chose to "implement it now" to finish M2.

Behavior

• A thread at or below CONFIG_EMB_TIMESLICE_PRIORITY (new; 255 means every level) gets CONFIG_EMB_TIMESLICE_TICKS at each dispatch.
• When the quantum expires, it is renewed. If an equal-priority peer is READY, a per-CPU rotation flag makes the next decision put the thread behind its peers. A preempted thread still resumes ahead of its peers (KRN-SCH-041) and gets a fresh quantum.
• The quantum is one more deadline in the tickless next-deadline computation, and one comparison in the periodic tick.
• Slicing needs the list scheduler; on the table scheduler each level holds a single thread. It is off by default, so every existing configuration builds the same kernel; T1 stays at 4056 / 39.
• A63 records the details for review: restart at dispatch, a yield without a peer, threshold changes while running, and the tickless counter.

Evidence

• Model: _slice_start and _slice_check mirror the kernel, plus a new appended TIMESLICE scenario group explored exhaustively. 129 model tests pass, up from 122.
• Bridge: the runner reports timeslice= and timeslice_prio= (only on slicing builds, so other captures stay byte-identical), and bridge.adapt adopts them.
  • New native-timeslice preset (quantum 2, threshold 20, periodic clock): seeds 1–3 × 40 runs gave 3560/3560 agreeing runs each.
  • Mutation check: a model without rotation diverges.
• Tickless: new native-timeslice-tickless preset, conformance only.
  • A tickless quantum starts from the free-running counter, which can run ahead of the delivered ticks the model counts. Measured: 1 divergence in 5 × 3560 runs.
  • On that build the bridge refuses the combination and the differential checks are not registered.
• Conformance: 4 new cases in test_sched.c, with a portable emb_test_spin_ticks() helper:
  • rotation behind every peer;
  • expiry without a peer;
  • two spinners sharing a level;
  • the threshold.
  • Mutation check: a kernel without rotation fails 2 of the 4.
• Local runs, all passing:
  • native gcc/clang/release/tiny/periodic/timeslice/timeslice-tickless/asan/tsan/coverage;
  • QEMU cm3, cm4 ×3, rv32 ×3;
  • AVR uno ×3, within footprint thresholds;
  • EmbSIM uno, nucleo and c3.
  • The docs build has the 9 known shim warnings; Python tool suites, generate --check and check-banned are clean.
• CI gains the native-timeslice and native-timeslice-tickless legs.

Docs

KRN-SCH-007/026/037/041 and KRN-TIM-029 statuses, SPEC-003 §8, the configuration guide (presets and scheduler options), the tasks guide, STATUS and CHANGELOG.