GeezerVison is showing github.com — fix(itertools): add re-entrancy guard to tee object by ever0de · Pull Request #5931 · RustPython/RustPython
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ever0de
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Jul 10, 2025
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edited by coderabbitai
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Reference
Summary by CodeRabbit
- Bug Fixes
- Improved stability of the tee iterator by preventing concurrent or recursive access, reducing the risk of runtime errors or inconsistent behavior. Users will now receive a clear error if re-entrancy is attempted.
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coderabbitai
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Jul 10, 2025
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edited
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Walkthrough
The PyItertoolsTeeData struct's values field was changed from a read-write lock to a mutex. The get_item method now uses a try_lock() on the mutex to detect re-entrance, returning a runtime error if the lock is already held, and caches iterator results accordingly.
Changes
| File(s) |
Change Summary |
| vm/src/stdlib/itertools.rs |
Changed values from PyRwLock<Vec<PyObjectRef>> to PyMutex<Vec<PyObjectRef>> in PyItertoolsTeeData. Updated new and get_item to use mutex locking with try_lock() and return error on re-entrance. |
Poem
A mutex now guards the tee's bright trail,
No more re-entry to make it fail.
Cached treasures locked tight in a row,
One hop at a time, steady and slow.
🐇🔐🌿
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Reviewing files that changed from the base of the PR and between aaf1805 and 17011c4.
📒 Files selected for processing (1)
vm/src/stdlib/itertools.rs (1 hunks)
🚧 Files skipped from review as they are similar to previous changes (1)
- vm/src/stdlib/itertools.rs
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if self.values.read().len() == index {
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let result = raise_if_stop!(self.iterable.next(vm)?);
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self.values.write().push(result);
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if self.locked.swap(true) {
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return Err(vm.new_runtime_error("cannot re-enter the tee iterator"));
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}
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let result = self.iterable.next(vm);
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self.locked.store(false);
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let obj = raise_if_stop!(result?);
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self.values.write().push(obj);
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}
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While traditional locks prefer to lock the code, Rust locks prefer to lock the data.
After changing PyRwLock to PyMutex, this approach will work
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if self.values.read().len() == index { |
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let result = raise_if_stop!(self.iterable.next(vm)?); |
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self.values.write().push(result); |
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if self.locked.swap(true) { |
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return Err(vm.new_runtime_error("cannot re-enter the tee iterator")); |
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} |
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let result = self.iterable.next(vm); |
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self.locked.store(false); |
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let obj = raise_if_stop!(result?); |
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self.values.write().push(obj); |
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} |
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let Some(values) = self.values.try_lock() else { |
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return Err(vm.new_runtime_error("cannot re-enter the tee iterator")); |
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}; |
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if values.len() == index { |
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let obj = raise_if_stop!(self.iterable.next(vm)?); |
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values.push(obj); |
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} |
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Ok(PyIterReturn::Return(values[index].clone())) |
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