Ensure thread safety for memory mappings. #6509
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nicola-cab
changed the title
finnschiermer
suggested changes
Apr 18, 2023
src/realm/alloc_slab.cpp
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| REALM_ASSERT(m_mappings.size()); | ||
| m_data = m_mappings[0].primary_mapping.get_addr(); | ||
| realm::util::encryption_read_barrier(m_mappings[0].primary_mapping, 0, sizeof(Header)); | ||
| { |
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Locking here should not be needed. The slab allocator is just being attached, and no other thread should have a reference to it at this point.
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@finnschiermer I think the assumption has changed or there is some other problem elsewhere, since |
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@nicola-cab Thx for highlighting this for me. Very interesting. |
…guard_for_mappings
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This PR although protects the mappings vector while reading the last committed format version, does not explain the other issues we have been seeing around the slab allocator. For now, I will keep them open and keep digging in. |
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What, How & Why?
It seems we are not always thread safe while accessing
m_mappingsinside the slab allocator.This could have caused #6508, but also it could be the cause of #6378 and #6510
Unfortunately, this is just a guess, since I haven't found a way to reproduce the issues yet.
☑️ ToDos