AsyncEventThread: fix race condition in stop#2994
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The AsyncEventThread releases the lock while executing user callbacks. If stop() is called during this time, it acquires the lock, sets `state_ = STOPPED`, signals the condition variable, and waits in `join()`. However, when the callback returned, the worker thread would re-acquire the lock and unconditionally set `state_ = IDLE`. This overwrote the `STOPPED` state, causing the thread to continue its loop instead of exiting. As a result, stop() would hang indefinitely in `join()`. This hang led to resource exhaustion and eventual memory corruption (manifesting as "Double free or corruption" in SPI tests) when the system attempted to forcefully clean up or reuse the stuck resources. This commit fixes the race by checking if the state is `STOPPED` after re-acquiring the lock, ensuring the thread exits correctly.
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The AsyncEventThread releases the lock while executing user callbacks. If stop() is called during this time, it acquires the lock, sets
state_ = STOPPED, signals the condition variable, and waits injoin().However, when the callback returned, the worker thread would re-acquire the lock and unconditionally set
state_ = IDLE. This overwrote theSTOPPEDstate, causing the thread to continue its loop instead of exiting. As a result, stop() would hang indefinitely injoin().This hang led to resource exhaustion and eventual memory corruption (manifesting as "Double free or corruption" in SPI tests) when the system attempted to forcefully clean up or reuse the stuck resources.
This commit fixes the race by checking if the state is
STOPPEDafter re-acquiring the lock, ensuring the thread exits correctly.