v2.2.0

Added

• Runtime version query API: coco_version(), coco_version_major(), coco_version_minor(), coco_version_patch().
• ENSURE_IN_CORO / ENSURE_IN_CORO_RET / ENSURE_IN_CORO_VOID guard macros for coroutine-only APIs, preventing crashes when called outside a coroutine context.
• POSIX signal block/unblock (coco_preempt_block_signal() / coco_preempt_unblock_signal()) with reference-counted nesting counter for critical section protection.
• P binding detection for coco_go(): when called from a worker thread, the new coroutine binds to the current P instead of scanning all processors.
• Periodic load balancing integrated into the worker loop (triggered every 100 coroutines processed).
• Linux netpoller wakeup uses eventfd instead of pipe for lower overhead.
• New examples: hot_stack, dynamic_stack, context_api.
• New benchmarks: bench_mt_sched, bench_hot_cold_switch; bench_io rewritten to measure actual coroutine I/O throughput.
• New tests: stress_mt_scaling, stress_channel_mt_burst, test_ctx_x86_64, test_preempt_block, test_preempt_channel, test_preempt_sched, test_coro_guard, test_sched_reinit, test_sched_balanced.
• Doxygen configuration for API reference generation.
• GitHub Actions CI workflow with sanitizer matrix (ASan, UBSan).
• Automated release workflow triggered on version tag push.

Changed

• coco_yield() return type changed from void to int (returns COCO_ERROR_INVALID when called outside a coroutine). ABI note: existing compiled objects must be recompiled.
• coro->state type changed from int (non-atomic) to _Atomic int for thread-safety. ABI note: existing compiled objects must be recompiled.
• Global runq wake strategy: targeted pthread_cond_signal replaces broadcast to fix thundering herd.

Fixed

• Multi-threaded scheduler data races and leaks:
  • coro->state is now _Atomic (acquire/release ordering).
  • stack_pool_multi protected by per-pool mutex.
  • Wrong-pool-free on work-stealing fixed via coro->stack_pool tracking.
• Channel wait_queue_lock and scheduler global_runq_lock / local_runq_lock critical sections protected from preemption.
• Scheduler reinitialization: coco_global_sched_stop() now fully cleans up state (queues, counters, locks).
• schedule_balanced() now actually redistributes coroutines from overloaded P's and releases hot-stack slots before migration.
• Worker thread H2 path now performs load balancing (extracted shared handle_coro_done helper).
• Windows APC preemption delivery: added alertable SleepEx in idle paths.
• Windows worker idle sleep capped to 1ms to prevent lost pthread_cond_signal wakeups.
• Windows I/O function linker conflicts between POSIX and Winsock implementations resolved.
• UBSan null-pointer in stress_channel_burst: hot-stack backup/restore now rewrites stack pointers in callee-saved registers.
• GCC 16 rbp clobber in sanitizer builds (-fomit-frame-pointer for register integrity test).
• Signal blocking nesting counter underflow guard in coco_preempt_unblock_signal().
• Munmap fallback in coco_global_sched_stop() queue cleanup when coro->stack_pool is NULL.