Re: [PATCH] RDMA/cma: Address sparse warnings

[Leon Romanovsky <leon@kernel.org>]

On Thu, Jun 08, 2023 at 04:07:13PM -0400, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> drivers/infiniband/core/cma.c:2090:13: warning: context imbalance in 'destroy_id_handler_unlock' - wrong count at exit
> drivers/infiniband/core/cma.c:2113:6: warning: context imbalance in 'rdma_destroy_id' - unexpected unlock
> drivers/infiniband/core/cma.c:2256:17: warning: context imbalance in 'cma_ib_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:2448:17: warning: context imbalance in 'cma_ib_req_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:2571:17: warning: context imbalance in 'cma_iw_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:2616:17: warning: context imbalance in 'iw_conn_req_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:3035:17: warning: context imbalance in 'cma_work_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:3542:17: warning: context imbalance in 'addr_handler' - unexpected unlock
> drivers/infiniband/core/cma.c:4269:17: warning: context imbalance in 'cma_sidr_rep_handler' - unexpected unlock

Strange, I was under impression that we don't have sparse errors in cma.c

> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  drivers/infiniband/core/cma.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> index 10a1a8055e8c..35c8d67a623c 100644
> --- a/drivers/infiniband/core/cma.c
> +++ b/drivers/infiniband/core/cma.c
> @@ -2058,7 +2058,7 @@ static void _destroy_id(struct rdma_id_private *id_priv,
>   * handlers can start running concurrently.
>   */
>  static void destroy_id_handler_unlock(struct rdma_id_private *id_priv)
> -	__releases(&idprv->handler_mutex)
> +	__must_hold(&idprv->handler_mutex)

According to the Documentation/dev-tools/sparse.rst
   64 __must_hold - The specified lock is held on function entry and exit.
   65
   66 __acquires - The specified lock is held on function exit, but not entry.
   67
   68 __releases - The specified lock is held on function entry, but not exit.

In our case, handler_mutex is unlocked while exiting from destroy_id_handler_unlock().

Thanks

>  {
>  	enum rdma_cm_state state;
>  	unsigned long flags;
> @@ -5153,7 +5153,6 @@ static void cma_netevent_work_handler(struct work_struct *_work)
>  	event.status = -ETIMEDOUT;
>  
>  	if (cma_cm_event_handler(id_priv, &event)) {
> -		__acquire(&id_priv->handler_mutex);
>  		id_priv->cm_id.ib = NULL;
>  		cma_id_put(id_priv);
>  		destroy_id_handler_unlock(id_priv);
> 
>