2020-02-19 09:36:44

by Amol Grover

Subject: [PATCH] sunrpc: Pass lockdep expression to RCU lists

detail->hash_table[] is traversed using hlist_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of detail->hash_lock.

Hence, add corresponding lockdep expression to silence false-positive
warnings, and harden RCU lists.

Signed-off-by: Amol Grover <[email protected]>
---
net/sunrpc/cache.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index f740cb51802a..5db5f5b94726 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -97,7 +97,8 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
spin_lock(&detail->hash_lock);

/* check if entry appeared while we slept */
- hlist_for_each_entry_rcu(tmp, head, cache_list) {
+ hlist_for_each_entry_rcu(tmp, head, cache_list,
+ lockdep_is_held(&detail->hash_lock)) {
if (detail->match(tmp, key)) {
if (cache_is_expired(detail, tmp)) {
hlist_del_init_rcu(&tmp->cache_list);
--
2.24.1

2020-03-03 16:37:55

by J. Bruce Fields

Subject: Re: [PATCH] sunrpc: Pass lockdep expression to RCU lists

On Wed, Feb 19, 2020 at 03:05:05PM +0530, Amol Grover wrote:
> detail->hash_table[] is traversed using hlist_for_each_entry_rcu
> outside an RCU read-side critical section but under the protection
> of detail->hash_lock.
>
> Hence, add corresponding lockdep expression to silence false-positive
> warnings, and harden RCU lists.

Thanks, applying for 5.7.--b.

>
> Signed-off-by: Amol Grover <[email protected]>
> ---
> net/sunrpc/cache.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index f740cb51802a..5db5f5b94726 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -97,7 +97,8 @@ static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
> spin_lock(&detail->hash_lock);
>
> /* check if entry appeared while we slept */
> - hlist_for_each_entry_rcu(tmp, head, cache_list) {
> + hlist_for_each_entry_rcu(tmp, head, cache_list,
> + lockdep_is_held(&detail->hash_lock)) {
> if (detail->match(tmp, key)) {
> if (cache_is_expired(detail, tmp)) {
> hlist_del_init_rcu(&tmp->cache_list);
> --
> 2.24.1