[WASM_WORKERS] Fix UB in pthread_mutex with debug+hybrid builds#26673
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@stephenduong1004 @walkingeyerobot I believe this is the fix we need to the issues we have been seeing internally with workers+pthreads hybrid builds. |
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I did end up finding a simpler/nicer repro test case for this. |
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This fix only applies to the hybrid Wasm Workers + pthread build mode. We can't currently rely on calling `pthread_self()` from a Wasm Worker, even the hybrid mode. We are working on fixing that in emscripten-core#26631. However, we do have a CURRENT_THREAD_ID macro that works on both Wasm Workers and pthreads. As it happens, pthread locks under musl do not normally depend on `pthread_self` except for "recursive" which need to access the `pthread_self()->tid` field to track the current owner. This means that I broke the debug + hybrid mode locks in emscripten-core#24607 because I added the recursion check to all locks in debug builds. While we do have a repro case for this which current crashes its not directly testing the issue, it just heppens to crash due to the current undefined behavior when doing `pthread_self()->tid` from a Wasm Worker. Fixes: emscripten-core#26619
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I don't suppose we could make __pthread_self()->tid work with Wasm Workers instead?
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We have a larger plan to try to make that work. See #26631. If we ever do make that work we can revert this partial solution. |
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This fix only applies to the hybrid Wasm Workers + pthread build mode.
We can't currently rely on calling
pthread_self()from a Wasm Worker, even the hybrid mode. We are working on fixing that in #26631. However, we do have aCURRENT_THREAD_IDmacro that works on both Wasm Workers and pthreads.As it happens, pthread locks under musl do not normally depend on
pthread_selfexcept for "recursive" which need to access thepthread_self()->tidfield to track the current owner. This means that I broke the debug + hybrid mode locks in #24607 because I added the recursion check to all locks in debug builds.While I have added a repro case for this its not directly testing the issue, it just heppens to crash due to the current undefined behavior when doing
pthread_self()->tidfrom a Wasm Worker.Fixes: #26619