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chore(buglog): bug-1897 fixed (0fe27d4b)

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Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Rongsong Shen 2026-10-01 03:46:06 +00:00
parent 0fe27d4be3
commit da5c3065ed
Signed by untrusted user: rshen
GPG key ID: 80533536B0EB651C
2 changed files with 17 additions and 14 deletions
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.wolf/bugs/bug-1897.md
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@ -1,8 +1,8 @@
---
id: "bug-1897"
status: "open"
status_updated: "2026-09-30"
status_note: "newly logged"
status: "fixed"
status_updated: "2026-10-01"
status_note: ""
component: "scheduler"
severity: "crash"
timestamp: "2026-09-30T10:19:59Z"
@ -11,6 +11,7 @@ occurrences: 1
files: ["src/scheduler/src/plugins/limit.c", "src/scheduler/src/snapshot_load.c"]
tags: ["scheduler", "sim", "snapshot", "limit"]
related: ["bug-1887", "bug-1888"]
fix_commits: ["0fe27d4b"]
---
# bug-1897: xce_scheduler --sim segfaults in limit_job_election on a job whose snapshot resreq failed to parse
@ -48,15 +49,15 @@ The replay's snapshot stores resreqs in the debug-dump format that bug-1888 wrot
- Evidence: `/home/claude/tmp/bug-1897/` (replay file copy, `run.out` with the ASan report, `sim.log`)
## Root cause
TODO: required for fixed/partial
UPDATE (2026-10-01): A job whose snapshot resreq fails to parse is kept by xce_sched_core_load_snapshot() (snapshot_load.c) with resreq and schedobj both NULL, so a running job's restored allocation stays charged. Nothing kept it out of the picker: the loader pushed it with on_job_push(), and in simulation mode sim_bootstrap_picker() (sim_picker.c) re-pushes every core job once the picker exists (bug-1567), which is the path the replay took, since the sim loads its snapshot before any picker is registered. The allocator thread (sched_allocator(), sched_election.c) then ran plugin_job_election() and sched_make_allocation() on the NULL schedobj, and limit_job_election() (limit.c:336) dereferenced it. Exposed since the bug-1887 fix made parse_resreq() reject the debug-dump resreq text that snapshots wrote before the bug-1888 fix, i.e. every replay captured before that fix; the live JOBS_PUSH path was never affected (core_build_job() drops such a job).
## Fix
TODO: required for fixed/partial
UPDATE (2026-10-01): A job without a schedobj is never made a picker candidate: snapshot_load.c skips on_job_push() for it (logging once that it will not be scheduled) and sim_picker.c's picker rebuild skips it too. The job stays in the core, so its restored allocation is still charged and later events still find it. As a backstop, sched_allocator() (sched_election.c) skips any picked job whose schedobj is NULL, the same way it skips a job it cannot find, so no other route into the picker can crash the allocator thread.
## Verification
- Test: TODO: name + file; RED before the fix, GREEN after
- Suites: TODO: suite results and build profile
- Live: TODO: soak/deploy run, or n/a and why
- Test: `test_snapshot_load_leaves_schedobj_null_when_resreq_fails_to_parse` (testsuite/test_snapshot_save_load.c, new no-picker-candidate assertion) RED ("Expected 0 Was 1"), GREEN after; `test_sched_allocator_skips_job_without_schedobj` (testsuite/test_sched_election_null_schedobj.c, new) RED (ASan SEGV in sched_make_allocation, scheduler.c:447), GREEN after; `test_snapshot_job_with_unparsable_resreq_is_not_scheduled` (testsuite/test_sim_event_loop.c, new) RED (a PEND decision for the job, with the sim_picker.c and sched_election.c changes reverted), GREEN after.
- Suites: scheduler ASAN suite 97/97 (build.alloc), 2026-10-01.
- Live: n/a for HA (no HA path touched). The original replay (`scheduler-replay-20260928-064842.replay`, `--sim`) completes all 1511 sessions in 3/3 runs: exit 0, no ASan report, the 50 affected jobs reported once at load as unschedulable, 0 allocator skips.
## References
- Related: none