fix: harden background-thread coalesced runtime work across reload#64
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Audit of the coalesced-drain change surfaced five concurrency issues, all addressed here: - gBgTimerExecutor was written without gTimerMutex while every reader holds it — a data race (UB) on std::function. Guard the assignment. - A transient ptr==0 drain leak-cleared the ENTIRE coalesced queue, permanently dropping main-runtime SharedRPC deliveries (no JS retry net). Keep queue.items intact; only disarm the drain latch. - nativeInvalidateSharedRpc left drainScheduled==true, stranding all future work after reload. Track the outstanding drain via scheduledDrainWorkId and clear the orphaned gPendingWork entry. - Recovery relied on a later enqueue to re-arm the drain, so items carried over a ptr==0 reload could strand until nativeDestroy. Make recovery structural: re-arm a drain in nativeInstallSharedBridge when the freshly installed runtime's queue is non-empty. - Closed a stale-id race where a concurrent invalidate empties the queue between drainRuntimeWorkQueue's remaining>0 check and the reschedule, by guarding scheduleRuntimeDrain against an empty queue.
Follow-up to the coalesced-drain hardening, addressing two reload-window issues found by a second audit pass: - Keeping queue.items across a ptr==0 reload (so the recovered runtime can drain them) let a background segment-eval lambda be replayed by install-recover AFTER drainPendingBgEvals had already settled it as retryable NO_RUNTIME — re-running evaluateJavaScript on the segment a second time. The eval lambda now treats an already-erased gPendingBgEvals entry as 'a drain claimed me, JS will retry' and skips the re-evaluation. - A drain posted just before reload can be silently discarded by the dead pre-reload JS thread, so its nativeDropScheduledWork never fires and drainScheduled stays stuck true. install-recover gated on !drainScheduled would then skip recovery and strand the items. It now force-arms a drain on the freshly installed runtime whenever the queue is non-empty; a still-live stale drain self-cancels via the empty-queue guard in scheduleRuntimeDrain.
…thread-coalesced-drain # Conflicts: # native-modules/react-native-background-thread/android/src/main/cpp/cpp-adapter.cpp # native-modules/react-native-background-thread/android/src/main/java/com/backgroundthread/BackgroundThreadManager.kt
ByteZhang1024
approved these changes
Jun 12, 2026
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Summary
加固 background-thread 的 coalesced runtime work 机制，修复 reload 期间的若干线程/状态问题。
fix: coalesce background thread runtime work— 将 runtime work 合并入队，减少跨线程调度开销fix: harden background-thread coalesced drain against threading bugs— 针对 coalesced drain 的线程安全加固fix: prevent bg-eval replay and latch-stall across reload— 修复 reload 时 bg-eval 重放与 drain latch 卡死；reload 过程中保留queue.items（main runtime 无 JS 重试网），仅复位 drain latch 让恢复后的 runtime 继续 drainchore: bump version to 3.0.63已合并最新
main（冲突以本分支为准）。Test plan