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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: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Joel Fernandes (Google) 2018-12-12 14:37:10 -08:00 committed by Paul E. McKenney
parent c2d8089de7
commit 423a86a610
1 changed files with 7 additions and 6 deletions
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13
include/linux/rcupdate.h
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@ -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)