diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-10-27 21:11:27 -0700 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-28 18:25:17 -0400 |
| commit | 54ef6df3f3f1353d99c80c437259d317b2cd1cbd (patch) | |
| tree | 22b1c691757577cb291430858def7d86d8449dfb | |
| parent | 5fecf3a1e1a0af61eb34eb6976ec9f59cca65d3f (diff) | |
rcu: Provide counterpart to rcu_dereference() for non-RCU situations
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>
| -rw-r--r-- | include/linux/rcupdate.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a4a819ffb2d1..53ff1a752d7e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -617,6 +617,21 @@ static inline void rcu_preempt_sleep_check(void) #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) /** + * 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_assign_pointer() - assign to RCU-protected pointer * @p: pointer to assign to * @v: value to assign (publish) |