70 lines
3.7 KiB
Markdown
70 lines
3.7 KiB
Markdown
---
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id: "bug-1955"
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status: "partial"
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status_updated: "2026-10-10"
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status_note: "covers a signal arriving after this host accepted the runtasks request; a control that reaches a remote host before its runtasks request arrives is still dropped there (needs a controller-side or pre-start record)"
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component: "worker"
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severity: "wrong-result"
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timestamp: "2026-10-10T08:46:10Z"
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last_seen: "2026-10-10T08:46:10Z"
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occurrences: 1
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files: ["src/worker/src/controller_connector.c"]
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tags: ["worker", "job-control", "parallel", "signal"]
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related: ["bug-1942", "bug-1908"]
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fix_commits: ["d3da3140"]
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gitea_issue: 386
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gitea_synced_status: "partial"
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gitea_synced_hash: "095558c6c67a"
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---
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# bug-1955: xcecd drops a signal for a remote task of a multi-host job that is still starting
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## Description
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**Observed:** (source reading, 2026-10-10; found while fixing bug-1942)
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Only the head host's job start opens the pending-signal window
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(`pending_signal_start(d->jobid)`, `src/worker/src/controller_connector.c:1062`,
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bug-1908). The runtasks handler for remote tasks (`handle_runtasks()`, `:1147`)
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never does, so a signal that arrives before the remote task's worker entry is
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registered is logged and dropped:
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```c
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XCECD_LOG(XCE_LOG_ERROR, "Failed to find worker for job ID: %s", jobidStr);
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FREEUP(task_ctx);
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return -1; /* controller_connector.c:1606 */
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```
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Since bug-1942 every host of a multi-host job receives job control, so this
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window is now reachable.
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**Expected:** like the head host (bug-1908), a signal for a remote task that
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is starting is kept and delivered once the task runs.
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**Impact:** wrong result: a kill or stop sent right after a multi-host job
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starts can miss some of its remote tasks, which keep running.
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**Found by:** review of the bug-1940/1942 fixes, 2026-10-10.
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## Environment
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- OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
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- libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
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- Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
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- Build: asan (xce.build)
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- Code: scheduler-framework @ 8568c8ab-dirty
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- Deployment: real `xcecd` worker (systemd/dbus); multi-host for the remote-task case
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## Reproduction
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1. Submit a multi-host job (e.g. `/xce-test-multihost` topology) and kill it
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immediately after dispatch.
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2. A remote host logs "Failed to find worker for job ID" and its task keeps
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running.
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- Frequency: deterministic by code reading (not yet run)
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- Evidence: the code quoted in Description; no logs kept.
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## Root cause
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Only the head-host start path opened the pending-signal window (`pending_signal_start`, `controller_connector.c`, bug-1908); `handle_runtasks()` queued remote tasks without it, so a signal arriving before the task's worker entry registered hit "Failed to find worker" and was dropped.
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## Fix
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`handle_runtasks()` calls `pending_signal_start(jobid)` before `submit_fork_task()` and takes it back if queuing fails; the existing RUNNING transition (`xcecd_worker_utils.c`, bug-1908) delivers the kept signal to the task.
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## Verification
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- Test: `test_jobcontrol_signal_for_queued_remote_task_is_kept` (`src/worker/testsuite/test_controller_connector.c`): RED `:1631: FAIL: Expected 0 Was -1. the kill must not be dropped`, GREEN after (32 tests, 0 failures).
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- Suites: `xce-build.sh all asan xce.build --incremental` on the merged branch, 2026-10-10: all C suites Ok 155 / Fail 0, frontend Go unit tests ok, xceadmin tests ok; apiserver `CGO_ENABLED=0 go test ./...` (incl. middleware, router, cmd) ok
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- Live: n/a: unit/fixture-level verification only; no live deployment was run (follow-up)
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## References
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- Fix commit: `d3da3140` (on `scheduler-framework`; worker-branch original in the merge)
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- Review: `.kiro/reviews/project-gap-review-2026-10-10.md`
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