Commit 423a86a6 authored by Joel Fernandes (Google)'s avatar Joel Fernandes (Google) Committed by Paul E. McKenney
Browse files

rcu: Add sparse check to rcu_assign_pointer() 



The rcu_assign_pointer() function currently doesn't do any sparse checking
on the assigned-to pointer.  So its possible that a pointer that is
not __rcu annotated is assigned with rcu_assign_pointer without sparse
complaints.  Because rcu_dereference() already does such checking,
this commit makes rcu_assign_pointer() to do the same. The extra
error could be helpful in cases where an RCU pointer is assigned with
rcu_assign_pointer() but not annotated with __rcu.

This doesn't generate any code in the normal case because __CHECKER__ is
defined only in the context of sparse.

This commit also renames rcu_dereference_sparse() to rcu_check_parse()
since the checking now happens not only during derereferencing but also
during assignment.

Test: Introduced an rcu_assign_pointer in code and checked the output of
sparse with and without this change. The change correctly causes sparse
to throw an error.

Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent c2d8089d

include/linux/rcupdate.h

+7 −6
Original line number Diff line number Diff line
@@ -309,16 +309,16 @@ static inline void rcu_preempt_sleep_check(void) { } 
 */



#ifdef __CHECKER__

#define rcu_dereference_sparse(p, space) \

#define rcu_check_sparse(p, space) \

	((void)(((typeof(*p) space *)p) == p))

#else /* #ifdef __CHECKER__ */

#define rcu_dereference_sparse(p, space)

#define rcu_check_sparse(p, space)

#endif /* #else #ifdef __CHECKER__ */



#define __rcu_access_pointer(p, space) \

({ \

	typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \

	rcu_dereference_sparse(p, space); \

	rcu_check_sparse(p, space); \

	((typeof(*p) __force __kernel *)(_________p1)); \

})

#define __rcu_dereference_check(p, c, space) \
@@ -326,13 +326,13 @@ static inline void rcu_preempt_sleep_check(void) { } 
	/* Dependency order vs. p above. */ \

	typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \

	RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \

	rcu_dereference_sparse(p, space); \

	rcu_check_sparse(p, space); \

	((typeof(*p) __force __kernel *)(________p1)); \

})

#define __rcu_dereference_protected(p, c, space) \

({ \

	RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \

	rcu_dereference_sparse(p, space); \

	rcu_check_sparse(p, space); \

	((typeof(*p) __force __kernel *)(p)); \

})

#define rcu_dereference_raw(p) \
@@ -382,6 +382,7 @@ static inline void rcu_preempt_sleep_check(void) { } 
#define rcu_assign_pointer(p, v)					      \

({									      \

	uintptr_t _r_a_p__v = (uintptr_t)(v);				      \

	rcu_check_sparse(p, __rcu);				      \

									      \

	if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL)	      \

		WRITE_ONCE((p), (typeof(p))(_r_a_p__v));		      \
@@ -785,7 +786,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 
 */

#define RCU_INIT_POINTER(p, v) \

	do { \

		rcu_dereference_sparse(p, __rcu); \

		rcu_check_sparse(p, __rcu); \

		WRITE_ONCE(p, RCU_INITIALIZER(v)); \

	} while (0)

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