Move and better-document waiting for thread exit #2839
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stevenengler
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This moves waiting for thread-exit from Process to ManagedThread, where it more logically belongs. It also adds a check in ManagedThread's Drop implementation to validate that we never drop it while the native thread is still running, and adds documentation about why this is important - to prevent memory corruption due to shared memory regions being deallocated and reused. This also fixes a bug - Before we *weren't* waiting for the thread to exit if the `clear_child_tid` attribute wasn't set. I belive this was a race condition, but in practice I think most higher level thread APIs (e.g. libc's `pthread` and Rust's `std::thread`) use this attribute, so wouldn't have wouldn't have been affected.
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On one last look I realized that while iterating on this I'd somehow dropped the documentation I'd added about why it's important not to drop ManagedThread while the native thread is still running 🤦 . Added this back in and on further reflection changed the drop implementation to always panic if the native thread is still running at drop time. |
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This moves waiting for thread-exit from
ProcesstoManagedThread, where it more logically belongs. It also adds a check inManagedThread'sDropimplementation to validate that we never drop it while the native thread is still running, and adds documentation about why this is important - to prevent memory corruption due to shared memory regions being deallocated and reused.This also fixes a bug - Before we weren't waiting for the thread to exit if the
clear_child_tidattribute wasn't set. I belive this was a race condition, but in practice I think most higher level thread APIs (e.g. libc'spthreadand Rust'sstd::thread) use this attribute, so wouldn't have wouldn't have been affected.