[PATCH v3 31/35] rhashtable: Enable capability analysis

Marco Elver
2025-09-18T14:06:52Z

Enable capability analysis for rhashtable, which was used as an initial
test as it contains a combination of RCU, mutex, and bit_spinlock usage.

Users of rhashtable now also benefit from annotations on the API, which
will now warn if the RCU read lock is not held where required.

Signed-off-by: Marco Elver <elver@google.com>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: linux-crypto@vger.kernel.org
---
v2:
* Remove disable/enable_capability_analysis() around headers.
---
include/linux/rhashtable.h | 14 +++++++++++---
lib/Makefile | 2 ++
lib/rhashtable.c | 5 +++--
3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index 6c85b28ea30b..347716b1ca37 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -245,16 +245,17 @@ void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
void rhashtable_walk_enter(struct rhashtable *ht,
struct rhashtable_iter *iter);
void rhashtable_walk_exit(struct rhashtable_iter *iter);
-int rhashtable_walk_start_check(struct rhashtable_iter *iter) __acquires(RCU);
+int rhashtable_walk_start_check(struct rhashtable_iter *iter) __acquires_shared(RCU);

static inline void rhashtable_walk_start(struct rhashtable_iter *iter)
+ __acquires_shared(RCU)
{
(void)rhashtable_walk_start_check(iter);
}

void *rhashtable_walk_next(struct rhashtable_iter *iter);
void *rhashtable_walk_peek(struct rhashtable_iter *iter);
-void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
+void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases_shared(RCU);

void rhashtable_free_and_destroy(struct rhashtable *ht,
void (*free_fn)(void *ptr, void *arg),
@@ -325,6 +326,7 @@ static inline struct rhash_lock_head __rcu **rht_bucket_insert(

static inline unsigned long rht_lock(struct bucket_table *tbl,
struct rhash_lock_head __rcu **bkt)
+ __acquires(__bitlock(0, bkt))
{
unsigned long flags;

@@ -337,6 +339,7 @@ static inline unsigned long rht_lock(struct bucket_table *tbl,
static inline unsigned long rht_lock_nested(struct bucket_table *tbl,
struct rhash_lock_head __rcu **bucket,
unsigned int subclass)
+ __acquires(__bitlock(0, bucket))
{
unsigned long flags;

@@ -349,6 +352,7 @@ static inline unsigned long rht_lock_nested(struct bucket_table *tbl,
static inline void rht_unlock(struct bucket_table *tbl,
struct rhash_lock_head __rcu **bkt,
unsigned long flags)
+ __releases(__bitlock(0, bkt))
{
lock_map_release(&tbl->dep_map);
bit_spin_unlock(0, (unsigned long *)bkt);
@@ -402,13 +406,14 @@ static inline void rht_assign_unlock(struct bucket_table *tbl,
struct rhash_lock_head __rcu **bkt,
struct rhash_head *obj,
unsigned long flags)
+ __releases(__bitlock(0, bkt))
{
if (rht_is_a_nulls(obj))
obj = NULL;
lock_map_release(&tbl->dep_map);
rcu_assign_pointer(*bkt, (void *)obj);
preempt_enable();
- __release(bitlock);
+ __release(__bitlock(0, bkt));
local_irq_restore(flags);
}

@@ -589,6 +594,7 @@ static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
static inline struct rhash_head *__rhashtable_lookup(
struct rhashtable *ht, const void *key,
const struct rhashtable_params params)
+ __must_hold_shared(RCU)
{
struct rhashtable_compare_arg arg = {
.ht = ht,
@@ -642,6 +648,7 @@ static inline struct rhash_head *__rhashtable_lookup(
static inline void *rhashtable_lookup(
struct rhashtable *ht, const void *key,
const struct rhashtable_params params)
+ __must_hold_shared(RCU)
{
struct rhash_head *he = __rhashtable_lookup(ht, key, params);

@@ -692,6 +699,7 @@ static inline void *rhashtable_lookup_fast(
static inline struct rhlist_head *rhltable_lookup(
struct rhltable *hlt, const void *key,
const struct rhashtable_params params)
+ __must_hold_shared(RCU)
{
struct rhash_head *he = __rhashtable_lookup(&hlt->ht, key, params);

diff --git a/lib/Makefile b/lib/Makefile
index 43b965046c2c..85a9144b008a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -50,6 +50,8 @@ lib-$(CONFIG_MIN_HEAP) += min_heap.o
lib-y += kobject.o klist.o
obj-y += lockref.o

+CAPABILITY_ANALYSIS_rhashtable.o := y
+
obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
list_sort.o uuid.o iov_iter.o clz_ctz.o \
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 3e555d012ed6..fe8dd776837c 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -358,6 +358,7 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
static int rhashtable_rehash_alloc(struct rhashtable *ht,
struct bucket_table *old_tbl,
unsigned int size)
+ __must_hold(&ht->mutex)
{
struct bucket_table *new_tbl;
int err;
@@ -392,6 +393,7 @@ static int rhashtable_rehash_alloc(struct rhashtable *ht,
* bucket locks or concurrent RCU protected lookups and traversals.
*/
static int rhashtable_shrink(struct rhashtable *ht)
+ __must_hold(&ht->mutex)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
unsigned int nelems = atomic_read(&ht->nelems);
@@ -724,7 +726,7 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
* resize events and always continue.
*/
int rhashtable_walk_start_check(struct rhashtable_iter *iter)
- __acquires(RCU)
+ __acquires_shared(RCU)
{
struct rhashtable *ht = iter->ht;
bool rhlist = ht->rhlist;
@@ -940,7 +942,6 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
* hash table.
*/
void rhashtable_walk_stop(struct rhashtable_iter *iter)
- __releases(RCU)
{
struct rhashtable *ht;
struct bucket_table *tbl = iter->walker.tbl;
--
2.51.0.384.g4c02a37b29-goog