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g_cleanup_queue was a file-scope MPSCQueue with a destructor, while the cleanup worker is a bthread that is never stopped: the bthread runtime itself is not destructed at exit (see the note in task_control.cpp), so the worker can still be inside Dequeue() when static destructors run. MPSCQueue's destructor drains the queue, turning that destruction into a second concurrent consumer of a single-consumer queue: _cur_dequeue_node is a plain pointer, so the destructor and the worker could pick and free the same node (double free) or interleave their advances (lost nodes). A timer callback firing during the destructor phase would additionally enqueue into a destroyed queue. No orderly teardown drains the queue at exit -- GlobalRelease only runs on init failure and in UT teardown -- so the residue the destructor would drain is really possible. Allocate the queue with new and never delete it, following the brpc convention for globals entangled with threads that never stop (g_task_control itself); the kernel reclaims it at exit. DrainAndWait observes g_cleanup_inflight, not the queue, so teardown semantics are unchanged. g_cleanup_inflight (trivially destructible atomics) and g_worker_mtx (a static initializer, nothing to destroy) keep their storage. Tested: cmake --build build --target brpc_ubring_unittest, and ./build/test/brpc_ubring_unittest (12/12 passed).
A failed bthread_start_background in Post() latched g_worker_unavailable forever, so every later cleanup fell back to running inline: the SDK calls went back to the process-wide timer thread (UbsShmDrainNode from UbsShmCallback, the delayed trx cleanups from their callbacks), delaying unrelated RPC timeouts, backup requests and bthread wakeups -- exactly what the worker exists to avoid. bthread creation fails transiently (ENOMEM), so the degradation correlated with memory pressure, the moment where blocking the timer thread hurts most, and it never self-healed. Drop the terminal flag and retry the lazy start on every post made while the worker is not started. A failed attempt leaves g_worker_started false and fails only that post; the caller runs it inline as the safety net, and the next post retries the start. The posting mutex already serializes the start attempt with the enqueue, so a job is still only ever queued behind a start that succeeded -- the flag was redundant double insurance for orphaned jobs. The error is logged with LOG_EVERY_SECOND so a failure window cannot spam. Add the g_ub_test_worker_start_rc hook so the new UT can inject a start failure deterministically (no real bthread is created while it is set), and cover both review cases: repeated failures fail only their own post and queue nothing, and the first post after the injection is cleared retries the start, runs the job exactly once and lets DrainAndWait observe quiescence. The suite must observe the worker in its unstarted state, so it is declared ahead of UBShmEndpointTest, whose teardown posts cleanups, and probes for an already-started worker to skip rather than assert on a start that is never attempted. Tested: cmake --build build --target brpc_ubring_unittest, and ./build/test/brpc_ubring_unittest (13/13 passed). Reintroducing the latch locally makes the new UT fail, confirming it guards the retry.
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