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Commit 995f1405 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by David Howells
Browse files

rcu: Suppress sparse warnings for rcu_dereference_raw() 



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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent c1adf200

include/linux/rcupdate.h

+6 −2
Original line number Diff line number Diff line
@@ -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.