[PATCH net-next 22/24] rcu: Suppress sparse warnings for rcu_dereference_raw()
From: David Howells
Date: Tue Jul 05 2016 - 09:14:56 EST
From: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Data structures that are used both with and without RCU protection
are difficult to write in a sparse-clean manner. If you mark the
relevant pointers with __rcu, sparse will complain about all non-RCU
uses, but if you don't mark those pointers, sparse will complain about
all RCU uses.
This commit therefore suppresses sparse warnings for rcu_dereference_raw(),
allowing mixed-protection data structures to avoid these warnings.
Reported-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
include/linux/rcupdate.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 5f1533e3d032..85830e6c797b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -611,6 +611,12 @@ static inline void rcu_preempt_sleep_check(void)
rcu_dereference_sparse(p, space); \
((typeof(*p) __force __kernel *)(p)); \
})
+#define rcu_dereference_raw(p) \
+({ \
+ /* Dependency order vs. p above. */ \
+ typeof(p) ________p1 = lockless_dereference(p); \
+ ((typeof(*p) __force __kernel *)(________p1)); \
+})
/**
* RCU_INITIALIZER() - statically initialize an RCU-protected global variable
@@ -729,8 +735,6 @@ static inline void rcu_preempt_sleep_check(void)
__rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \
__rcu)
-#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/
-
/*
* The tracing infrastructure traces RCU (we want that), but unfortunately
* some of the RCU checks causes tracing to lock up the system.