diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-10-27 21:11:27 -0700 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-08-25 16:56:59 +0200 |
| commit | afadae320b2116f9a4dee89fd431f3c1ab64103e (patch) | |
| tree | 52aa192ed6e699ba744f2f57ff863859f04a46a1 | |
| parent | ad3b8fca4a918003cc03e8546b2f35506fd5d2e7 (diff) | |
rcu: Provide counterpart to rcu_dereference() for non-RCU situations
commit 54ef6df3f3f1353d99c80c437259d317b2cd1cbd upstream.
Although rcu_dereference() and friends can be used in situations where
object lifetimes are being managed by something other than RCU, the
resulting sparse and lockdep-RCU noise can be annoying. This commit
therefore supplies a lockless_dereference(), which provides the
protection for dereferences without the RCU-related debugging noise.
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | include/linux/rcupdate.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f1f1bc39346b..4912c953cab7 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -554,6 +554,20 @@ static inline void rcu_preempt_sleep_check(void) (p) = (typeof(*v) __force space *)(v); \ } while (0) +/** + * lockless_dereference() - safely load a pointer for later dereference + * @p: The pointer to load + * + * Similar to rcu_dereference(), but for situations where the pointed-to + * object's lifetime is managed by something other than RCU. That + * "something other" might be reference counting or simple immortality. + */ +#define lockless_dereference(p) \ +({ \ + typeof(p) _________p1 = ACCESS_ONCE(p); \ + smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ + (_________p1); \ +}) /** * rcu_access_pointer() - fetch RCU pointer with no dereferencing |