2020-01-18 04:29:57

by Amol Grover

Subject: [PATCH v2] drivers: soc: ti: knav_qmss_queue: Pass lockdep expression to RCU lists

inst->handles is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of knav_dev_lock.

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

Add macro for the corresponding lockdep expression.

Signed-off-by: Amol Grover <[email protected]>
---
v2:
- Remove rcu_read_lock_held() from lockdep expression since it is
implicitly checked for.

drivers/soc/ti/knav_qmss_queue.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/ti/knav_qmss_queue.c b/drivers/soc/ti/knav_qmss_queue.c
index 1ccc9064e1eb..37f3db6c041c 100644
--- a/drivers/soc/ti/knav_qmss_queue.c
+++ b/drivers/soc/ti/knav_qmss_queue.c
@@ -25,6 +25,8 @@

static struct knav_device *kdev;
static DEFINE_MUTEX(knav_dev_lock);
+#define knav_dev_lock_held() \
+ lockdep_is_held(&knav_dev_lock)

/* Queue manager register indices in DTS */
#define KNAV_QUEUE_PEEK_REG_INDEX 0
@@ -52,8 +54,9 @@ static DEFINE_MUTEX(knav_dev_lock);
#define knav_queue_idx_to_inst(kdev, idx) \
(kdev->instances + (idx << kdev->inst_shift))

-#define for_each_handle_rcu(qh, inst) \
- list_for_each_entry_rcu(qh, &inst->handles, list)
+#define for_each_handle_rcu(qh, inst) \
+ list_for_each_entry_rcu(qh, &inst->handles, list, \
+ knav_dev_lock_held())

#define for_each_instance(idx, inst, kdev) \
for (idx = 0, inst = kdev->instances; \
--
2.24.1

2020-01-18 18:08:08

by Santosh Shilimkar

Subject: Re: [PATCH v2] drivers: soc: ti: knav_qmss_queue: Pass lockdep expression to RCU lists

On 1/17/20 8:24 PM, Amol Grover wrote:
> inst->handles is traversed using list_for_each_entry_rcu
> outside an RCU read-side critical section but under the protection
> of knav_dev_lock.
>
> Hence, add corresponding lockdep expression to silence false-positive
> lockdep warnings, and harden RCU lists.
>
> Add macro for the corresponding lockdep expression.
>
> Signed-off-by: Amol Grover <[email protected]>
> ---
> v2:
> - Remove rcu_read_lock_held() from lockdep expression since it is
> implicitly checked for.
>
Thanks.
Acked-by: Santosh Shilimkar <[email protected]>

> drivers/soc/ti/knav_qmss_queue.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/ti/knav_qmss_queue.c b/drivers/soc/ti/knav_qmss_queue.c
> index 1ccc9064e1eb..37f3db6c041c 100644
> --- a/drivers/soc/ti/knav_qmss_queue.c
> +++ b/drivers/soc/ti/knav_qmss_queue.c
> @@ -25,6 +25,8 @@
>
> static struct knav_device *kdev;
> static DEFINE_MUTEX(knav_dev_lock);
> +#define knav_dev_lock_held() \
> + lockdep_is_held(&knav_dev_lock)
>
> /* Queue manager register indices in DTS */
> #define KNAV_QUEUE_PEEK_REG_INDEX 0
> @@ -52,8 +54,9 @@ static DEFINE_MUTEX(knav_dev_lock);
> #define knav_queue_idx_to_inst(kdev, idx) \
> (kdev->instances + (idx << kdev->inst_shift))
>
> -#define for_each_handle_rcu(qh, inst) \
> - list_for_each_entry_rcu(qh, &inst->handles, list)
> +#define for_each_handle_rcu(qh, inst) \
> + list_for_each_entry_rcu(qh, &inst->handles, list, \
> + knav_dev_lock_held())
>
> #define for_each_instance(idx, inst, kdev) \
> for (idx = 0, inst = kdev->instances; \
>