_gtaskqueue_start_threads() reports total thread-creation failure as success; queue teardown lifecycle is stubbed, so a half-born queue silently hangs all future drainers

Summary

If lwkt_create() fails, _gtaskqueue_start_threads() NULLs the slot, skips tq_tcount++ and still returns 0 unconditionally — the comment's promised cleanup points at gtaskqueue_free(), which is static __unused dead code, and taskqgroup_destroy() is an empty stub. A queue whose threads failed to start still accepts enqueues and wakes nobody; its tasks never run; any drain on it sleeps forever (timo=0) with no error. Silent permanent kernel-thread hang under thread-table/ kmem exhaustion at queue-start time. No deterministic guest PoC (code-path analysis; findings/poc/DF-2850/NOTES.md).

Recommended fix

Track successful creates, tear down partial state and return the error; make TASKQGROUP_DEFINE's SYSINIT treat a failed queue as fatal at boot; implement or delete the dead destroy/free declarations.

Timeline

• 2026-09-02 Discovered during pass-2 audit of subr_gtaskqueue.c (GLM 5.3).