fix(itertools): add re-entrancy guard to tee object #5931
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Jul 10, 2025
vm/src/stdlib/itertools.rs
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| if self.values.read().len() == index { | ||
| let result = raise_if_stop!(self.iterable.next(vm)?); | ||
| self.values.write().push(result); | ||
| if self.locked.swap(true) { | ||
| return Err(vm.new_runtime_error("cannot re-enter the tee iterator")); | ||
| } | ||
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| let result = self.iterable.next(vm); | ||
| self.locked.store(false); | ||
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| let obj = raise_if_stop!(result?); | ||
| self.values.write().push(obj); | ||
| } | ||
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There was a problem hiding this comment.
While traditional locks prefer to lock the code, Rust locks prefer to lock the data.
After changing PyRwLock to PyMutex, this approach will work
Suggested change
| if self.values.read().len() == index { | |
| let result = raise_if_stop!(self.iterable.next(vm)?); | |
| self.values.write().push(result); | |
| if self.locked.swap(true) { | |
| return Err(vm.new_runtime_error("cannot re-enter the tee iterator")); | |
| } | |
| let result = self.iterable.next(vm); | |
| self.locked.store(false); | |
| let obj = raise_if_stop!(result?); | |
| self.values.write().push(obj); | |
| } | |
| let Some(values) = self.values.try_lock() else { | |
| return Err(vm.new_runtime_error("cannot re-enter the tee iterator")); | |
| }; | |
| if values.len() == index { | |
| let obj = raise_if_stop!(self.iterable.next(vm)?); | |
| values.push(obj); | |
| } | |
| Ok(PyIterReturn::Return(values[index].clone())) |
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