• Thomas Hellstrom's avatar
    kref: Implement kref_get_unless_zero v3 · 4b20db3d
    Thomas Hellstrom authored
    
    This function is intended to simplify locking around refcounting for
    objects that can be looked up from a lookup structure, and which are
    removed from that lookup structure in the object destructor.
    Operations on such objects require at least a read lock around
    lookup + kref_get, and a write lock around kref_put + remove from lookup
    structure. Furthermore, RCU implementations become extremely tricky.
    With a lookup followed by a kref_get_unless_zero *with return value check*
    locking in the kref_put path can be deferred to the actual removal from
    the lookup structure and RCU lookups become trivial.
    
    v2: Formatting fixes.
    v3: Invert the return value.
    Signed-off-by: default avatarThomas Hellstrom <thellstrom@vmware.com>
    Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
    4b20db3d
kref.h 4.18 KB