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deadlock thread
Hi. We have weird trouble related to the multi-threading. Does anyone have ideas how to resolve or avoid? Sample Code // sample.hpp class Sample { public: Sample(); ~Sample(); void Init(); void Dealloc(); void OnEvent(); private: std::mutex sample_mutex_; int counter = 1; } // sample.cpp #include "sample.hpp" Sample::Sample() {} Sample::~Sample() {} void Sample::Init() { std::async([]() { std::this_thread::sleep_for(std::chrono::seconds(2)); this->OnEvent(); }); } void Sample::Dealloc() { std::lock_guard<std::mutex> lock(sample_mutex_); counter = 0; } void Sample::OnEvent { // called from another thread std::lock_guard<std::mutex> lock(sample_mutex_); counter += 1; } // obj_sample.h @interface ObjSample : NSObject - (id _Nonnull)init; @property(nonatomic, readonly) std::shared_ptr<Sample> sample; @end // obj_sample.mm @implementation ObjSample - (id _Nonnull)init{ if (self = [super init]) { _sample = std::make_shared<Sample>(); _sample->Init(); } return self; } - (void)dealloc { sample->Dealloc(); } @end What happens the deadlock happens. according to the debug navigator with the Xcode, we figured out 2 facts below. OnEvent does not end although it looks completed. void Sample::OnEvent { // called from another thread std::lock_guard<std::mutex> lock(sample_mutex_); counter += 1; } // <= Thread 35: stop here Sample::Dealloc is run on the same thread of OnEvent. // debug navigator Thread 35 2 Sample::Dealloc <- this is weird. 3 Sample::OnEvent We guess they causes the deadlock. probability less than 10% Environment MacOS: 14.3.1(Apple M1) Xcode: 15.3 iOS Simulator: 17.0.1
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Apr ’24