Commit bee8a520 authored by Herbert Xu's avatar Herbert Xu
Browse files

rhashtable: Use rcu_dereference_all and rcu_dereference_all_check 



Add rcu_dereference_all and rcu_dereference_all_check so that
library code such as rhashtable can be used with any RCU variant.

As it stands rcu_dereference is used within rashtable, which
creates false-positive warnings if the user calls it from another
RCU context, such as preempt_disable().

Use the rcu_dereference_all and rcu_dereference_all_check calls
in rhashtable to suppress these warnings.

Also replace the rcu_dereference_raw calls in the list iterators
with rcu_dereference_all to uncover buggy calls.

Reported-by: default avatarMenglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent f75f6668

include/linux/rcupdate.h

+26 −0
Original line number Diff line number Diff line
@@ -713,6 +713,24 @@ do { \ 
				(c) || rcu_read_lock_sched_held(), \

				__rcu)



/**

 * rcu_dereference_all_check() - rcu_dereference_all with debug checking

 * @p: The pointer to read, prior to dereferencing

 * @c: The conditions under which the dereference will take place

 *

 * This is similar to rcu_dereference_check(), but allows protection

 * by all forms of vanilla RCU readers, including preemption disabled,

 * bh-disabled, and interrupt-disabled regions of code.  Note that "vanilla

 * RCU" excludes SRCU and the various Tasks RCU flavors.  Please note

 * that this macro should not be backported to any Linux-kernel version

 * preceding v5.0 due to changes in synchronize_rcu() semantics prior

 * to that version.

 */

#define rcu_dereference_all_check(p, c) \

	__rcu_dereference_check((p), __UNIQUE_ID(rcu), \

				(c) || rcu_read_lock_any_held(), \

				__rcu)



/*

 * The tracing infrastructure traces RCU (we want that), but unfortunately

 * some of the RCU checks causes tracing to lock up the system.
@@ -767,6 +785,14 @@ do { \ 
 */

#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)



/**

 * rcu_dereference_all() - fetch RCU-all-protected pointer for dereferencing

 * @p: The pointer to read, prior to dereferencing

 *

 * Makes rcu_dereference_check() do the dirty work.

 */

#define rcu_dereference_all(p) rcu_dereference_all_check(p, 0)



/**

 * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism

 * @p: The pointer to hand off

include/linux/rhashtable.h

+7 −7
Original line number Diff line number Diff line
@@ -272,13 +272,13 @@ struct rhash_lock_head __rcu **rht_bucket_nested_insert( 
	rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))



#define rht_dereference_rcu(p, ht) \

	rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))

	rcu_dereference_all_check(p, lockdep_rht_mutex_is_held(ht))



#define rht_dereference_bucket(p, tbl, hash) \

	rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))



#define rht_dereference_bucket_rcu(p, tbl, hash) \

	rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))

	rcu_dereference_all_check(p, lockdep_rht_bucket_is_held(tbl, hash))



#define rht_entry(tpos, pos, member) \

	({ tpos = container_of(pos, typeof(*tpos), member); 1; })
@@ -373,7 +373,7 @@ static inline struct rhash_head *__rht_ptr( 
static inline struct rhash_head *rht_ptr_rcu(

	struct rhash_lock_head __rcu *const *bkt)

{

	return __rht_ptr(rcu_dereference(*bkt), bkt);

	return __rht_ptr(rcu_dereference_all(*bkt), bkt);

}



static inline struct rhash_head *rht_ptr(
@@ -497,7 +497,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
	for (({barrier(); }),						\

	     pos = head;						\

	     !rht_is_a_nulls(pos);					\

	     pos = rcu_dereference_raw(pos->next))

	     pos = rcu_dereference_all(pos->next))



/**

 * rht_for_each_rcu - iterate over rcu hash chain
@@ -513,7 +513,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
	for (({barrier(); }),					\

	     pos = rht_ptr_rcu(rht_bucket(tbl, hash));		\

	     !rht_is_a_nulls(pos);				\

	     pos = rcu_dereference_raw(pos->next))

	     pos = rcu_dereference_all(pos->next))



/**

 * rht_for_each_entry_rcu_from - iterated over rcu hash chain from given head
@@ -560,7 +560,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
 * list returned by rhltable_lookup.

 */

#define rhl_for_each_rcu(pos, list)					\

	for (pos = list; pos; pos = rcu_dereference_raw(pos->next))

	for (pos = list; pos; pos = rcu_dereference_all(pos->next))



/**

 * rhl_for_each_entry_rcu - iterate over rcu hash table list of given type
@@ -574,7 +574,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, 
 */

#define rhl_for_each_entry_rcu(tpos, pos, list, member)			\

	for (pos = list; pos && rht_entry(tpos, pos, member);		\

	     pos = rcu_dereference_raw(pos->next))

	     pos = rcu_dereference_all(pos->next))



static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,

				     const void *obj)