Fix thread safety bug in split sender notify#1361
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ericniebler merged 1 commit intoNVIDIA:mainfrom Jul 6, 2024
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ccotter
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Jul 5, 2024
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| STDEXEC_ASSERT(__waiters_copy.front() != __get_tombstone()); | ||
| for (__local_state_base* __item: __waiters_copy) { | ||
| for (auto __itr = __waiters_copy.begin(); __itr != __waiters_copy.end(); ) { |
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I didn't find this fix all that satisfying (it seems a little too "cute"). Open to suggestions here. I considered changing the intrusive slist to handle this better, since the intrusive nature of the data structure leaves the iterator open to such bugs, but that didn't seem like the right thing to do.
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If we find any more bugs with the "split is thread-safe" test, we'll need to consider renaming the test! |
Notifying the `local_state` might cause it to be destructed, whiich means the instrusive list's increment might be accessing uninitialized memory. Fixes NVIDIA#1354 Test plan: I was able to fairly reliably reproduce the TSAN and MSAN diagnostics by defining `local_state_base`'s destructor to set `__next_=nullptr` and adding a `sleep(25ms)` as the first line in `__notify_waiters`. With the fix, I could run the TSAN and MSAN executables for a few minutes and never saw any errors.
ericniebler
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Jul 5, 2024
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/ok to test |
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The CI failure seems unrelated? |
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THANK YOU so much for finding an fixing this bug. 🎉
yes, unrelated. it only happens with nvc++. i haven't gotten to the bottom of it. |
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Notifying the
local_statemight cause it to be destructed, whiich means the instrusive list's increment might be accessing uninitialized memory.Fixes #1354
Test plan: I was able to fairly reliably reproduce the TSAN and MSAN diagnostics by defining
local_state_base's destructor to set__next_=nullptrand adding asleep(25ms)as the first line in__notify_waiters. With the fix, I could run the TSAN and MSAN executables for a few minutes and never saw any errors.