Call trace_object on an empty space #102
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C-bug
Category: Bug
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This was referenced Mar 9, 2022
qinsoon
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Mar 10, 2022
If a binding uses `ObjectReference` to point to an address that is not within our allocated memory, the SFT and the side metadata for the `ObjectReference` may not be initialized properly. This PR introduces a solution by introducing a constant `ObjectModel::OBJECT_REF_OFFSET_BEYOND_CELL`. If a binding may use object reference to point to an address beyond the cell we allocate, they need to provide a `Some` value for the constant. MMTk allocators need to guarantee that the object reference for an allocation won't point to a new chunk (so its metadata is properly initialized and is the same as the allocation result). This PR fixes mmtk/mmtk-jikesrvm#102. This PR: * introduces a constant `ObjectModel::OBJECT_REF_OFFSET_BEYOND_CELL`. By default, it is `None`. If a binding may use `ObjectReference` to point to an address outside a cell, they need to set the constant to a proper `Some` value. * Introduces a module `util::alloc::object_ref_guard`, which includes a few methods that help allocators to check and avoid breaking the invariant. * adds a few assertions to check if our allocation addresses and object references have valid SFT entries. * introduces a space acquire lock so we can guarantee when pages are acquired from a page resource, the SFT for the pages are always initialized. * removes unnecessary methods in `Map32`.
qinsoon
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Mar 10, 2022
This PR updates MMTk core to mmtk/mmtk-core#555, and fixes #102
tianleq
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Apr 4, 2022
If a binding uses `ObjectReference` to point to an address that is not within our allocated memory, the SFT and the side metadata for the `ObjectReference` may not be initialized properly. This PR introduces a solution by introducing a constant `ObjectModel::OBJECT_REF_OFFSET_BEYOND_CELL`. If a binding may use object reference to point to an address beyond the cell we allocate, they need to provide a `Some` value for the constant. MMTk allocators need to guarantee that the object reference for an allocation won't point to a new chunk (so its metadata is properly initialized and is the same as the allocation result). This PR fixes mmtk/mmtk-jikesrvm#102. This PR: * introduces a constant `ObjectModel::OBJECT_REF_OFFSET_BEYOND_CELL`. By default, it is `None`. If a binding may use `ObjectReference` to point to an address outside a cell, they need to set the constant to a proper `Some` value. * Introduces a module `util::alloc::object_ref_guard`, which includes a few methods that help allocators to check and avoid breaking the invariant. * adds a few assertions to check if our allocation addresses and object references have valid SFT entries. * introduces a space acquire lock so we can guarantee when pages are acquired from a page resource, the SFT for the pages are always initialized. * removes unnecessary methods in `Map32`.
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I started to see this error in #101
This is potentially a bug introduced by MMTk SFT trace object: mmtk/mmtk-core@e85d997
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