Mitigate deadlock on DLL unload #16416
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🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/16416
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Summary: ThreadPool gets stored in a static variable here extension/threadpool/threadpool.cpp:146 This means the destructor of ThreadPool will be run when the process exits or a DLL containing this code unloads. While working with ExecuTorch I experienced a deadlock during unloading our DLL (which contained ExecuTorch) at runtime. This was caused by the pthreadpool_destroy function pthreadpool/src/windows.c:366 waiting forever on the worker threads. Why this is happening exactly is unclear to me. It is likely a race condition inside Windows Parallel Loader (https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown) as I could see its functions in the stack trace of the stuck worker threads after they returned from their main function. The issue was mitigated on my side by calling `executorch::extension::threadpool::get_threadpool()->_unsafe_reset_threadpool(0);` before unloading the DLL. This is just a workaround. I think a proper fix would be to rework the ThreadPool singleton and allow for explicit termination of it. Differential Revision: D89889628
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Summary: ThreadPool gets stored in a static variable here extension/threadpool/threadpool.cpp:146 This means the destructor of ThreadPool will be run when the process exits or a DLL containing this code unloads. While working with ExecuTorch I experienced a deadlock during unloading our DLL (which contained ExecuTorch) at runtime. This was caused by the pthreadpool_destroy function pthreadpool/src/windows.c:366 waiting forever on the worker threads. Why this is happening exactly is unclear to me. It is likely a race condition inside Windows Parallel Loader (https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown) as I could see its functions in the stack trace of the stuck worker threads after they returned from their main function. The issue was mitigated on my side by calling `executorch::extension::threadpool::get_threadpool()->_unsafe_reset_threadpool(0);` before unloading the DLL. This is just a workaround. I think a proper fix would be to rework the ThreadPool singleton and allow for explicit termination of it. Reviewed By: kimishpatel Differential Revision: D89889628
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Summary: ThreadPool gets stored in a static variable here extension/threadpool/threadpool.cpp:146 This means the destructor of ThreadPool will be run when the process exits or a DLL containing this code unloads. While working with ExecuTorch I experienced a deadlock during unloading our DLL (which contained ExecuTorch) at runtime. This was caused by the pthreadpool_destroy function pthreadpool/src/windows.c:366 waiting forever on the worker threads. Why this is happening exactly is unclear to me. It is likely a race condition inside Windows Parallel Loader (https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown) as I could see its functions in the stack trace of the stuck worker threads after they returned from their main function. The issue was mitigated on my side by calling `executorch::extension::threadpool::get_threadpool()->_unsafe_reset_threadpool(0);` before unloading the DLL. This is just a workaround. I think a proper fix would be to rework the ThreadPool singleton and allow for explicit termination of it. Reviewed By: kimishpatel Differential Revision: D89889628
Summary: ThreadPool gets stored in a static variable here extension/threadpool/threadpool.cpp:146 This means the destructor of ThreadPool will be run when the process exits or a DLL containing this code unloads. While working with ExecuTorch I experienced a deadlock during unloading our DLL (which contained ExecuTorch) at runtime. This was caused by the pthreadpool_destroy function pthreadpool/src/windows.c:366 waiting forever on the worker threads. Why this is happening exactly is unclear to me. It is likely a race condition inside Windows Parallel Loader (https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown) as I could see its functions in the stack trace of the stuck worker threads after they returned from their main function. The issue was mitigated on my side by calling `executorch::extension::threadpool::get_threadpool()->_unsafe_reset_threadpool(0);` before unloading the DLL. This is just a workaround. I think a proper fix would be to rework the ThreadPool singleton and allow for explicit termination of it. Reviewed By: kimishpatel Differential Revision: D89889628
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Summary:
ThreadPool gets stored in a static variable here extension/threadpool/threadpool.cpp:146
This means the destructor of ThreadPool will be run when the process exits or a DLL containing this code unloads.
While working with ExecuTorch I experienced a deadlock during unloading our DLL (which contained ExecuTorch) at runtime. This was caused by the pthreadpool_destroy function pthreadpool/src/windows.c:366 waiting forever on the worker threads.
Why this is happening exactly is unclear to me. It is likely a race condition inside Windows Parallel Loader (https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown) as I could see its functions in the stack trace of the stuck worker threads after they returned from their main function.
The issue was mitigated on my side by calling
executorch::extension::threadpool::get_threadpool()->_unsafe_reset_threadpool(0);before unloading the DLL.This is just a workaround. I think a proper fix would be to rework the ThreadPool singleton and allow for explicit termination of it.
Differential Revision: D89889628