From 4b20db3de8dab005b07c74161cb041db8c5ff3a7 Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Tue, 6 Nov 2012 11:31:49 +0000 Subject: [PATCH] kref: Implement kref_get_unless_zero v3 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: Thomas Hellstrom Signed-off-by: Dave Airlie --- Reading git-format-patch failed