3721f6df39
hurt to have it in the repository. git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22990 a95241bf-73f2-0310-859d-f6bbb57e9c96
53 lines
2.1 KiB
Plaintext
53 lines
2.1 KiB
Plaintext
Locks/Reference Counting:
|
|
|
|
vm_address_space:
|
|
sem R/W for area creation/deletion and any other address space changes
|
|
fields: areas, area_hint (is currently written in vm_area_lookup() without a write lock!),
|
|
state
|
|
ref_count: ensures validity of object beyond team lifetime,
|
|
retrieved via the global sAddressSpaceTable's pointer (which is guarded by
|
|
sAddressSpaceHashSem)
|
|
vm_address_space_walk_next() is unsafe! (and obsolete, only used by the former
|
|
page scanner)
|
|
Problems: resize_area() does not lock any address spaces yet, but needs to lock all clones
|
|
|
|
vm_area:
|
|
ref_count: ensures validity
|
|
retrieved via the global sAreaHash's pointer (which is guarded by
|
|
sAreaHashLock)
|
|
vs. vm_area_lookup() which iterates over the address space's area list, not
|
|
the hash - therefore, it checks ref_count against NULL (ugly)
|
|
variable fields:
|
|
size, protection: essentially unguarded! (can be changed by resize_area()
|
|
and set_area_protection())
|
|
mappings: guarded by the global sMappingLock (currently a spinlock)
|
|
address_space_next: vm_address_space::sem
|
|
hash_next: sAreaHashLock
|
|
cache: guarded by vm_area_get_locked_cache()/sAreaCacheLock
|
|
cache_next|prev: cache_ref::lock
|
|
|
|
vm_cache_ref:
|
|
ref_count: ensures validity
|
|
vm_cache_remove_consumer(): does scary things with the ref_count
|
|
fault_acquire_locked_source(): tries to get a ref through the vm_cache
|
|
cache, areas: guarded by lock
|
|
|
|
vm_cache:
|
|
all fields: guarded by ref::lock
|
|
BUT: ref may change, therefore it's generally unsafe to go from cache to ref
|
|
without holding the ref's lock (which happens, by design, in vm_cache::source
|
|
and vm_cache::consumers)!
|
|
|
|
vm_page:
|
|
hash_next: guarded by sPageCacheTableLock spinlock
|
|
queue_prev|next: guarded by sPageLock
|
|
cache_prev|next, cache, cache_offset: guarded by vm_cache_ref::lock
|
|
mappings: guarded by the global sMappingLock (currently a spinlock)
|
|
state: in vm_page only used with the sPageLock held, other uses have the
|
|
cache locked the page is in
|
|
wired_count, usage_count: not guarded? TBD
|
|
busy_reading, busy_writing: dummy pages only
|
|
|
|
vm_translation_map:
|
|
TBD.
|