[Linux-kernel-mentees] [PATCH 1/3] infiniband: hw: hfi1: verbs.c: Use built-in RCU list checking

madhuparnabhowmik04 at gmail.com madhuparnabhowmik04 at gmail.com
Wed Jan 8 08:08:50 UTC 2020


From: madhuparnabhowmik04 at gmail.com

From: Jason Gunthorpe <jgg at ziepe.ca>

On Wed, Jan 08, 2020 at 12:59:12AM +0530, madhuparnabhowmik04 at gmail.com wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik04 at gmail.com>
> 
> list_for_each_entry_rcu has built-in RCU and lock checking.
> Pass cond argument to list_for_each_entry_rcu.
> 
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04 at gmail.com>
>  drivers/infiniband/hw/hfi1/verbs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
> index 089e201d7550..e6abdbcb4ffb 100644
> +++ b/drivers/infiniband/hw/hfi1/verbs.c
> @@ -515,7 +515,8 @@ static inline void hfi1_handle_packet(struct hfi1_packet *packet,
>  				       opa_get_lid(packet->dlid, 9B));
>  		if (!mcast)
>  			goto drop;
> -		list_for_each_entry_rcu(p, &mcast->qp_list, list) {
> +		list_for_each_entry_rcu(p, &mcast->qp_list, list,
> +					lock_is_held(&(ibp->rvp.lock).dep_map)) {

Why .dep_map? Does this compile?

Yes, it compiles.

Alternatively, it can be lockdep_is_held(ibp->rvp.lock).
Please refer to the macro(link below) and let me know if the usage of lock_is_held()
in the patch is correct.

https://elixir.bootlin.com/linux/v5.5-rc2/source/include/linux/lockdep.h#L364

Thanks,
Madhuparna

Jason


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