rcu: Suppress sparse warnings for rcu_dereference_raw() (995f1405) · Commits · 戴 / test

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@redhat.com> Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:

David Howells <dhowells@redhat.com>

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.

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