forked from lei.chen/myxce
Rongsong Shen
bfe69b1e85
Using gdb (SIGQUIT all-thread backtrace on the wedged nodes), nailed the round-4 blocker to a deterministic ABBA lock-order deadlock in src/lib async dispatch — identical on both wedged survivors: - io_worker (netio.c:672): holds ep->lock, blocks on q->lock (vtask_enq->dataq_enq) - vdispatcher dataq_deq (dataq.c:65): holds q->lock, blocks on ep->lock via the vtask_eligible (vtaskmgr.c:255) -> endpoint_is_task_blocked (netio.c:1001) cb io_worker wedges -> node stops accepting/answering PreVotes -> two restarted survivors can't elect -> round-4 stall. The release SIGSEGV is the same ep/q race corrupting under churn. Defect: dataq_deq runs its match callback while holding q->lock, and the callback takes ep->lock — inverting io_worker's ep->lock->q->lock order. Minimal fix: make ep->busy atomic + lockless in endpoint_is_task_blocked (or io_worker drops ep->lock before dataq_enq, or one global lock order). Ownership: src/lib async-I/O dispatch (vtaskmgr/dataq/netio) = raft-drive-async / core libxce, a Non-Goal of this spec. Per upstream-ownership protocol, routed to raft-drive-async (bug-1282); 7.2 stays blocked until the dispatch lock-order is repaired, then re-run the gate. The gate worked as designed — 7.2 must be GREEN before raft-drive-async flips dispatch flags ON, and it caught a real dispatch deadlock. Task 5.4 (root-cause + assign ownership) is DONE. Consensus correctness (Phase-2/5.2/5.3) is unaffected. Co-Authored-By: Claude <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019dbTHR9CsEYK9RsqmQpQpC |
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