colin-r-schultz opened a new issue, #45371:
URL: https://github.com/apache/arrow/issues/45371
### Describe the bug, including details regarding any error messages,
version, and platform.
The following example test case, when run under TSAN, reports a data race.
```cpp
TEST_F(TestRecordBatch, ColumnsThreadSafety) {
const int length = 10;
random::RandomArrayGenerator gen(42);
std::shared_ptr<ArrayData> array_data = gen.ArrayOf(utf8(),
length)->data();
auto schema = ::arrow::schema({field("f1", utf8())});
auto record_batch = RecordBatch::Make(schema, length, {array_data});
std::atomic_bool start_flag{false};
std::thread t([record_batch, &start_flag]() {
start_flag.store(true);
auto columns = record_batch->columns();
ASSERT_EQ(columns.size(), 1);
});
// Wait for thread startup
while (!start_flag.load()) {
};
auto columns = record_batch->columns();
ASSERT_EQ(columns.size(), 1);
t.join();
}
```
The relevant definitions in `record_batch.cc` are below
```cpp
const std::vector<std::shared_ptr<Array>>& columns() const override {
for (int i = 0; i < num_columns(); ++i) {
// Force all columns to be boxed
column(i);
}
return boxed_columns_;
}
std::shared_ptr<Array> column(int i) const override {
std::shared_ptr<Array> result = std::atomic_load(&boxed_columns_[i]);
if (!result) {
result = MakeArray(columns_[i]);
std::atomic_store(&boxed_columns_[i], result);
}
return result;
}
```
The `columns()` method returns a reference to `mutable boxed_columns_`,
assuming that it is fully initialized and will not be written to again.
However, multiple threads can race to initialize `boxed_columns_[i]`, leading
to additional atomic writes after `column(i)` has been called for the first
time. These atomic writes can race against non atomic reads of the
`boxed_columns_` vector after it is returned by `columns()`. This is undefined
behavior and can lead to a use-after-free of the contained `Array`s.
### Component(s)
C++
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