Violates this project's own recorded Decision Log entry: "No client
reply-wait timeout as a fix for a hung request -- fail loud at the real
transport/source instead of masking with a deadline backstop."
OPCode_schedAdmin (cluster.c) and on_fetchfile (job.c, the worker proxy
-- cluster.c's own comment says schedAdmin "mirrors on_fetchfile's proxy
pattern", confirming one shared design mistake, not two independent
bugs) both blocked on a multi-second pthread_cond_timedwait, replying
"timeout" on expiry. handle_scheduler_leave()/handle_worker_leave() (the
actual disconnect handlers) only nulled the endpoint pointer -- neither
ever signaled the pending waiter, so a mid-wait disconnect was invisible
until the deadline lapsed. The timeout was the ONLY failure-detection
mechanism, exactly what the decision forbids.
Both sites already had a working signal function on their success path
(schedadmin_signal(), fetchfile_signal()) -- just never wired to the
disconnect handlers. Fixed by calling them from
handle_scheduler_leave()/handle_worker_leave() with a distinguishable
-ECONNRESET outcome, so the waiter wakes immediately on disconnect
instead of only on the deadline. Timeouts kept as defensive backstops
for a genuinely wedged peer that never disconnects cleanly either --
this fix is about not relying SOLELY on the timeout, not removing it.
schedadmin_signal_disconnect() must be called BEFORE handle_scheduler_leave()
acquires c->sched.lock -- the dispatch wait holds that same lock for its
entire duration, so signaling after acquiring it would deadlock.
Found by an /xce-audit-invariants controller pass (Decision Log fidelity
dimension). New test_fetchfile_disconnect.c plus extensions to
test_sched_admin_dispatch.c/test_sched_worker_change.c; RED/GREEN
independently verified against real elapsed-time assertions (pre-fix:
5001ms full-timeout wait; post-fix: <1s immediate wake). Full controller
suite: 1181 tests, 2 failures -- both the pre-existing, unrelated
bug-1561 overlayfs sandbox flake, confirmed via a clean meson-driven run.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AgYRU3zDTqNGV5Jk8aiKLg
sched_worker_change() aliased w->host.resvals_to_sched to a local xlist_t's
backing array, pushed it to the scheduler, then freed that array via
xlist_fini() without resetting the alias - leaving a dangling pointer for
the rest of the worker's life. On disconnect (handle_worker_leave ->
mark_worker_unavail -> persist_worker_hook_fun -> capnp_encode_worker ->
encode_Worker -> encode_NameValue_list), this dereferenced freed memory and
crashed the controller - but only once a scheduler had ever connected
(on_scheduler_join gates the hook registration), which made it easy to miss
in isolated worker-only testing.
The correct reset already existed in the function but was dead-code'd
behind #if 0 /*FIXME*/ - apparently from a prior fix attempt that got
wrapped instead of landed. Fix mirrors the proven-correct pattern already
used by the sibling apiserver_worker_change(): null the alias before
xlist_fini() frees the backing array, rather than double-freeing via
free_name_val_list() first.
Adds test_sched_worker_change.c, a regression test driving the real
production hook-dispatch path (xce_run_hooks -> sched_worker_hook_fun ->
sched_worker_dead -> sched_worker_change) and the real encode_Worker()
encoder the original crash traversed - confirmed to reproduce the exact
ASAN heap-use-after-free when the fix is reverted, and pass clean when
restored, closing the gap that let this regress silently once already.
Found while live-testing the resource-value-verification feature (deploying
a scheduler + injecting worker resource values via xce_test, then
disconnecting) - unrelated to that feature's own changes.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
