The dispatcher checked each queued task's endpoint busy flag one item at a
time, while the vcpu that finished the endpoint's previous message cleared
the flag without the taskq lock (a lock there deadlocked, bug-1282). Within
one scan, task N was skipped (endpoint still busy), the endpoint freed up,
and task N+1 of the SAME endpoint was dequeued first. Standby controllers
then handled WAL catch-up entry 258 before 257 and NACKed (log mismatch):
26 reorders -> ~576 NACKs in a 45-min production-like run, both standbys
at once at 21:39:24, primary lost its write quorum and answered
jobdispatch/join with E_XCE_NOT_READY, the scheduler client failed over and
rejoined, and the rejoin JOBS_PUSH carried lagging committed state
("refusing resync state ... existing job is RUN" WARNs).
dataq gains dataq_deq_ctx() (a per-scan matcher context). The scan is now
vtask_deq_eligible(taskq, is_blocked): it remembers every endpoint found
busy and keeps all later tasks of that endpoint ineligible for the rest of
the scan (past 64 distinct busy endpoints, every later IO task waits for
the next scan) -- per-endpoint FIFO without any new lock.
Test lib/testsuite/test_vtask_order.c injects is_blocked to free the
endpoint mid-scan: task N+1 was dequeued before the fix, none after; other
endpoints and FIFO/generic tasks unaffected. Suites: lib 1/1, controller
5/5, worker 10/10, scheduler 87/87, harness 5/5. Chaotic HA soak 2/2 PASS
with 0 WAL reorders (2 and 5 per run before), no ASAN.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Lands the PeerCtrlDispatch machinery behind a DEFAULT-OFF flag
(g_drive_async_peerctrl_dispatch_enabled); production behavior is
UNCHANGED. peer_ctrl_msg_handler becomes a thin shim that takes
ownership of ep->fsm_in.pkt and either runs the routing body inline
(flag OFF, byte-for-byte the prior path) or dispatches it to the vtask
pool via vtask_enq_classified (flag ON). The 3 routers now take pkt as
an explicit param (no cross-thread ep->fsm_in.pkt re-read). Per-endpoint
arrival order is enforced by bind_vtask's endpoint_block_tasks.
Packet ownership: shim clears ep->fsm_in.pkt at dispatch (sole-owner
transfer); peer_ctrl_vtask_entry NULLs iod->pkt before the body frees
it once. New vtask_t.owns_io_pkt (default 0) lets taskq_item_killer free
the carried packet for an un-executed queued task at vtaskmgr_fini WITHOUT
double-freeing the libxce endpoint-owned path (bug-1199).
Adversarial review found two FLAG-ON hazards, documented with loud
comments (flag is OFF so production is unaffected), to be resolved before
task 3.4 flips the flag ON:
- bug-1197 (CRITICAL): raft_cb_become_follower endpoint_fini()s peer
vote-eps from a pool worker, racing the io_worker's read of ep->data;
needs iomgr_unmonitor before endpoint_fini in every pool-reachable
teardown.
- bug-1198 (HIGH): peer_ctrl_classify tags all work VTASK_LIVENESS, but
the CTRL_PRIMARY repl-ack path can run a blocking snapshot checkpoint
inline; resolved by task 3.2 (offload snapshot to SlowLane).
Per spec, 3.1 is not 'done' until the task 3.4 deadlock gate is green.
Tests: 3 new peerctrl tests; controller 196/196, lib 282/0; 0 net leaks.
vtaskmgr gains vtask_class_t (LIVENESS/LIVE_BLOCK/REQ_BLOCK) + a pool-level
blocking reservation: REQ_BLOCK fast-rejects -XCE_ERR_NOT_READY past
n_vcpus-R; LIVENESS never gated (deadlock-freedom). commit_submit folds its
inflight_waits onto the pool via commit_set_pool; production wired in
cluster.c phase2 (vtaskmgr_set_liveness_reserved(R) + commit_set_pool).
Lock order p->lock->ce->lock->blk_lock. Dormant until 3.1. Commit suites
38/30/22/38 green; lib 282/0, controller 196/0, ASAN clean. Phase 1 done.
