53 lines
2.1 KiB
Plaintext
53 lines
2.1 KiB
Plaintext
Locks/Reference Counting:
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vm_address_space:
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sem R/W for area creation/deletion and any other address space changes
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fields: areas, area_hint (is currently written in vm_area_lookup() without a write lock!),
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state
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ref_count: ensures validity of object beyond team lifetime,
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retrieved via the global sAddressSpaceTable's pointer (which is guarded by
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sAddressSpaceHashSem)
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vm_address_space_walk_next() is unsafe! (and obsolete, only used by the former
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page scanner)
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Problems: resize_area() does not lock any address spaces yet, but needs to lock all clones
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vm_area:
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ref_count: ensures validity
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retrieved via the global sAreaHash's pointer (which is guarded by
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sAreaHashLock)
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vs. vm_area_lookup() which iterates over the address space's area list, not
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the hash - therefore, it checks ref_count against NULL (ugly)
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variable fields:
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size, protection: essentially unguarded! (can be changed by resize_area()
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and set_area_protection())
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mappings: guarded by the global sMappingLock (currently a spinlock)
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address_space_next: vm_address_space::sem
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hash_next: sAreaHashLock
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cache: guarded by vm_area_get_locked_cache()/sAreaCacheLock
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cache_next|prev: cache_ref::lock
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vm_cache_ref:
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ref_count: ensures validity
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vm_cache_remove_consumer(): does scary things with the ref_count
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fault_acquire_locked_source(): tries to get a ref through the vm_cache
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cache, areas: guarded by lock
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vm_cache:
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all fields: guarded by ref::lock
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BUT: ref may change, therefore it's generally unsafe to go from cache to ref
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without holding the ref's lock (which happens, by design, in vm_cache::source
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and vm_cache::consumers)!
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vm_page:
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hash_next: guarded by sPageCacheTableLock spinlock
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queue_prev|next: guarded by sPageLock
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cache_prev|next, cache, cache_offset: guarded by vm_cache_ref::lock
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mappings: guarded by the global sMappingLock (currently a spinlock)
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state: in vm_page only used with the sPageLock held, other uses have the
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cache locked the page is in
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wired_count, usage_count: not guarded? TBD
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busy_reading, busy_writing: dummy pages only
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vm_translation_map:
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TBD.
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