Fix[bmqp::RequestManager]: unsafe read without mutex - #1713
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The justification to use reinterpret_cast used in bmqp::RequestManager is incorrect now, possible to simplify and remove it. Signed-off-by: Evgeny Malygin <emalygin@bloomberg.net>
bmqp::RequestManager docs mention invariant: all requests must be cancelled in the same order as they recorded. This commit adds a test for it. Signed-off-by: Evgeny Malygin <emalygin@bloomberg.net>
The existing code reads map bucket count without holding a mutex. Other thread might cause rehashing as we are reading this value, leading to UB. Signed-off-by: Evgeny Malygin <emalygin@bloomberg.net>
678098
commented
Aug 14, 2026
| BSLA_MAYBE_UNUSED bsl::pair<RequestMapIter, bool> | ||
| insertRC = requestsCopy.insert( | ||
| bsl::make_pair(it->first, it->second)); | ||
| BSLS_ASSERT_SAFE(insertRC.second); |
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We iterate through bmqc::OrderedHashMap so we have guarantee that keys in this map are unique. Due to this, insert return codes checks are redundant. Moreover, we don't need a second map here and can use a vector
678098
commented
Aug 14, 2026
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| // Create a new map so we can work on it outside the mutex | ||
| RequestMap requestsCopy(d_requests.bucket_count(), | ||
| d_requests.get_allocator()); |
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d_requests.bucket_count() is not thread-safe: this call here was a bug
678098
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Aug 14, 2026
| { | ||
| bslmt::LockGuard<bslmt::Mutex> guard(&d_mutex); // MUTEX LOCKED | ||
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| requestsCopy.reserve(d_requests.size()); |
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This reserve might over-reserve memory, if we are cancelling only a small part of all requests. This raises a question what is better: dynamic resizes or one resize for a possibly big chunk of memory.
I think one allocation is better here
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reinterpret_castvector, not themap, to iterate through the requests that has to be cancelled