[PATCH v4 31/35] rhashtable: Enable context analysis

Enable context 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 <[email protected]>
Cc: Thomas Graf <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: [email protected]
---
v4:
* Rename capability -> context analysis.

v2:
* Remove disable/enable_context_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 05a221ce79a6..5ba7356d79f0 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 __always_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 __always_inline struct rhash_head *__rhashtable_lookup(
 static __always_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 __always_inline void *rhashtable_lookup_fast(
 static __always_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 2e983f37d173..4ca9e8ce66bb 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
 
+CONTEXT_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 fde0f0e556f8..6074ed5f66f3 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;
-- 
2.52.0.rc1.455.g30608eb744-goog