[chassisd] Capture DPU reboot cause via boot_id and add midplane-down reason for Smart Switch by chartsai-nvidia · Pull Request #850 · sonic-net/sonic-platform-daemons

chartsai-nvidia · 2026-07-02T19:23:53Z

Why I did it

On Smart Switch platforms, chassisd needs a reliable way to detect when a DPU has
rebooted and to record the correct reboot cause for it. The previous approach inferred
reboots from midplane operational-status transitions and time-window heuristics, which was
fragile and could miss or misattribute reboots. This change switches to a deterministic
signal: the DPU publishes its kernel boot_id, and the NPU captures the reboot cause
whenever that boot_id changes. It also adds a proper midplane-down reason
(Planned vs. Unplanned) per HLD rev 0.7.

Work item tracking

Microsoft ADO (number only): N/A

How I did it

DPU side (DpuStateUpdater / DpuStateManagerTask): read the kernel boot_id from
/proc/sys/kernel/random/boot_id and publish it into the DPU_STATE table in
CHASSIS_STATE_DB, updating it only when it changes.
NPU side (SmartSwitchModuleUpdater): add check_dpu_boot_id_changes() to capture and
persist the reboot cause when a DPU's boot_id changes (only while the midplane is
reachable), and load persisted boot_ids on startup from previous-reboot-cause.json.
Add RebootCauseSubscriberTask, which subscribes to DPU_STATE changes and triggers
reboot-cause capture on boot_id updates, replacing the old status-transition /
time-window reboot heuristic.
Persist boot_id alongside the reboot-cause record and simplify the history file naming
by removing the separate prev_reboot_time.txt bookkeeping.
Add _resolve_midplane_down_reason() to classify midplane up->down transitions as
Planned (from the STATE_DB transition flag/type) or Unplanned (from the platform's
get_midplane_down_reason()), and write it into dpu_midplane_link_reason.
Reuse the platform-agnostic ChassisBase.REBOOT_CAUSE_* constants for midplane-down
reasons instead of redefining equivalent constants in the module mock.

How to verify it

cd sonic-chassisd
pytest tests/test_chassisd.py

Tests were added or updated in tests/test_chassisd.py and tests/mock_platform.py to
cover boot_id capture and the Planned/Unplanned midplane-down reason logic. The targeted
midplane-down reason tests passed with 7 tests.

mssonicbld · 2026-07-02T19:24:01Z

/azp run

azure-pipelines · 2026-07-02T19:24:11Z

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mssonicbld · 2026-07-04T02:57:20Z

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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chartsai-nvidia · 2026-07-07T20:06:53Z

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mssonicbld · 2026-07-08T11:22:50Z

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mssonicbld · 2026-07-09T11:23:24Z

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mssonicbld · 2026-07-10T11:23:57Z

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mssonicbld · 2026-07-11T11:21:28Z

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mssonicbld · 2026-07-12T11:20:48Z

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mssonicbld · 2026-07-13T11:19:44Z

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mssonicbld · 2026-07-14T11:19:46Z

Hi @sonic-net/sonic-platform-daemons-maintainer, this approved PR has workflow run(s) waiting for approval. Please help review. Thanks!

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chartsai-nvidia · 2026-07-14T22:03:36Z

/azpw retry

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mssonicbld · 2026-07-15T11:22:51Z

Hi @sonic-net/sonic-platform-daemons-maintainer, this approved PR has workflow run(s) waiting for approval. Please help review. Thanks!

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mssonicbld · 2026-07-16T11:23:42Z

Hi @sonic-net/sonic-platform-daemons-maintainer, this approved PR has workflow run(s) waiting for approval. Please help review. Thanks!

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chartsai-nvidia · 2026-07-16T20:28:20Z

/azpw retry

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Retrying failed(or canceled) stages in build 1154977:

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mssonicbld · 2026-07-17T11:23:25Z

Hi @sonic-net/sonic-platform-daemons-maintainer, this approved PR has workflow run(s) waiting for approval. Please help review. Thanks!

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mssonicbld · 2026-07-20T21:35:39Z

/azp run

azure-pipelines · 2026-07-20T21:35:48Z

Azure Pipelines: Successfully started running 1 pipeline(s).

mssonicbld · 2026-07-21T06:47:06Z

This PR has backport request label(s) for branch(es): 202605, but is missing required test information. Please make sure you tick the tested branch(es) in the Tested branch section and provide test evidence (e.g., 202605: <test result>) in the Test result section as well in your PR description.

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NPU chassisd able to read boot_id and update and persist add subscribe to chassisd add tests add persist previous midplane down reason Signed-off-by: Charles Tsai <chartsai@nvidia.com>

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

mssonicbld · 2026-07-21T16:23:50Z

/azp run

azure-pipelines · 2026-07-21T16:24:01Z

Azure Pipelines: Successfully started running 1 pipeline(s).

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

mssonicbld · 2026-07-23T16:47:50Z

/azp run

azure-pipelines · 2026-07-23T16:48:01Z

Azure Pipelines: Successfully started running 1 pipeline(s).

chartsai-nvidia · 2026-07-23T17:57:53Z

/azpw retry

mssonicbld · 2026-07-23T17:57:56Z

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mssonicbld · 2026-07-23T17:57:59Z

Retrying failed(or canceled) stages in build 1173081:

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chartsai-nvidia · 2026-07-23T19:24:29Z

/azpw retry

mssonicbld · 2026-07-23T19:30:29Z

Retrying failed(or canceled) jobs...

chartsai-nvidia · 2026-07-23T22:30:05Z

/azpw retry

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mssonicbld · 2026-07-23T22:30:10Z

Retrying failed(or canceled) stages in build 1173081:

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Signed-off-by: Charles Tsai <chartsai@nvidia.com>

mssonicbld · 2026-07-24T01:13:17Z

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Azure Pipelines: Successfully started running 1 pipeline(s).

chartsai-nvidia mentioned this pull request Jul 2, 2026

[PMON HLD] update get_reboot_cause mechanism and add get_midplane_dow… sonic-net/SONiC#2385

Open

dgsudharsan added the Request for 202605 Branch label Jul 7, 2026

dgsudharsan previously approved these changes Jul 7, 2026

View reviewed changes

chartsai-nvidia dismissed dgsudharsan’s stale review via 4d84d9d July 20, 2026 21:35

DPU able to publish boot_id

981d39f

NPU chassisd able to read boot_id and update and persist add subscribe to chassisd add tests add persist previous midplane down reason Signed-off-by: Charles Tsai <chartsai@nvidia.com>

chartsai-nvidia added 3 commits July 21, 2026 19:10

fix test errors

ba6cff4

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

fix flake8

ca23aa8

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

fix tests

c3ded96

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

chartsai-nvidia force-pushed the chartsai/pmon-hld-update branch from 4d84d9d to c3ded96 Compare July 21, 2026 16:23

mssonicbld added the Cherry Pick Conflict_202605 label Jul 21, 2026

dgsudharsan removed Request for 202605 Branch Cherry Pick Conflict_202605 labels Jul 21, 2026

fix test coverage

960cb0e

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

fix tests to use shared chassis reboot causes

c51bd29

Signed-off-by: Charles Tsai <chartsai@nvidia.com>

chartsai-nvidia requested a review from dgsudharsan July 24, 2026 16:59

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Why I did it

Work item tracking

How I did it

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