linux-kernel - Re: [PATCH 3/3] infiniband: sw: rdmavt: mcast.c: Use built-in RCU list checking

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Date:   Fri, 14 Feb 2020 12:26:34 -0500
From:   Dennis Dalessandro <dennis.dalessandro@...el.com>
To:     madhuparnabhowmik04@...il.com, mike.marciniszyn@...el.com,
        jgg@...pe.ca, paulmck@...nel.org
Cc:     joel@...lfernandes.org, frextrite@...il.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        rcu@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] infiniband: sw: rdmavt: mcast.c: Use built-in RCU
 list checking

On 1/14/2020 11:25 AM, madhuparnabhowmik04@...il.com wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>
> 
> Use built-in RCU and lock-checking for list_for_each_entry_rcu()
> by passing the cond argument.
> 
> Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>
> ---
>   drivers/infiniband/sw/rdmavt/mcast.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/mcast.c b/drivers/infiniband/sw/rdmavt/mcast.c
> index dd11c6fcd060..31c7f12c7665 100644
> --- a/drivers/infiniband/sw/rdmavt/mcast.c
> +++ b/drivers/infiniband/sw/rdmavt/mcast.c
> @@ -224,7 +224,7 @@ static int rvt_mcast_add(struct rvt_dev_info *rdi, struct rvt_ibport *ibp,
>   		}
>   
>   		/* Search the QP list to see if this is already there. */
> -		list_for_each_entry_rcu(p, &tmcast->qp_list, list) {
> +		list_for_each_entry_rcu(p, &tmcast->qp_list, list, lockdep_is_held(&(ibp->lock))) {
>   			if (p->qp == mqp->qp) {
>   				ret = ESRCH;
>   				goto bail;
> 

This one is OK. The lock is held and it is the correct one to use when 
updating the list.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@...el.com>