---
id: "bug-1893"
status: "open"
status_updated: "2026-09-30"
status_note: "newly logged"
component: "scheduler"
severity: "wrong-result"
timestamp: "2026-09-30T03:58:52Z"
last_seen: "2026-09-30T03:58:52Z"
occurrences: 1
files: ["src/scheduler/src/plugins/seqjob_allocator.c", "src/scheduler/src/plugins/parjob_allocator.c"]
tags: ["scheduler", "allocation", "preason", "code-review"]
related: ["bug-1892"]
---

# bug-1893: xce_scheduler allocators add spurious resource-0 shared pend reasons (loop reads past unmet list)

## Description
**Observed:** found by code reading, so there is no failing run yet. When the shared-resource check
fails, both allocators add the pend reasons with
```c
for (i = 0; i < ctx->alloc_req.shared.count; i++) {
    rc = vget(core->resmgr, ((int*)ctx->unmeet.idxs.data)[i], (void**)&r);
    if (rc <= 0) continue;
    add_job_preason(reason->reasons, PREASON_NO_RESOURCE, NULL, r->name);
}
```
(`seqjob_allocator.c` `my_alloc`, `parjob_allocator.c` `my_alloc`). The loop
bound is the number of *requested* shared resources, but `ctx->unmeet` holds
only the *unmet* ones, packed at `[0, unmeet.count)` by `unsatisfy_()`
(`resource.c:152-165`). Its arrays were `calloc`ed with capacity
`shared.count` (`resource.c:280`), so entries `[unmeet.count, shared.count)`
are 0.

**Expected:** iterate `i < ctx->unmeet.count` (as the host path does,
`resource.c:566`), giving one `NO_RESOURCE` reason per unmet shared resource.

**Impact:** wrong pend reason, noise level. When a job requests N shared
resources and only M < N are unmet, the loop adds N - M extra
`PREASON_NO_RESOURCE` reasons naming whatever resource has index 0 (if one
exists), which that job may never have requested. Main reason and allocation
decision are unaffected. No out-of-bounds memory access (the tail is inside the
allocation).

**Found by:** review of the `scheduler-allocator-runner` requirements
(2026-09-29); the loop moves into the framework runner in that spec.

## Environment
- OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
- libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
- Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
- Build: asan (xce.build)
- Code: scheduler-framework @ a370d724-dirty
- Deployment: n/a: found by code reading; any deployment where a job requests 2+ shared resources and only some are short

## Reproduction
1. `git checkout a370d724`; read the loop in
   `src/scheduler/src/plugins/seqjob_allocator.c` / `parjob_allocator.c`
   `my_alloc()` (after `sched_check_shared_satisfy`), and
   `src/scheduler/src/resource.c:130-169,266-316`.
2. Unit-test sketch: resource idx 0 = `slots`; two shared resources A (idx 7,
   plenty) and B (idx 8, total 0); a seqjob primary requesting 1 of each.
   Expected: exactly one host-less reason (`NO_RESOURCE`, res "B"); today a
   second reason names `slots`.
- Frequency: deterministic (by code reading; no test exercises it yet)
- Evidence: not kept (code reading only)

## Root cause
TODO: required for fixed/partial

## Fix
TODO: required for fixed/partial

## 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

## References
- Related: none