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

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Date:   Tue, 14 Jan 2020 12:00:19 -0500
From:   Dennis Dalessandro <dennis.dalessandro@...el.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, madhuparnabhowmik04@...il.com
Cc:     mike.marciniszyn@...el.com, paulmck@...nel.org,
        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 1/3] infiniband: hw: hfi1: verbs.c: Use built-in RCU list
 checking

On 1/14/2020 11:57 AM, Jason Gunthorpe wrote:
> On Tue, Jan 14, 2020 at 09:53:45PM +0530, madhuparnabhowmik04@...il.com wrote:
>> From: Madhuparna Bhowmik <madhuparnabhowmik04@...il.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@...il.com>
>>   drivers/infiniband/hw/hfi1/verbs.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
>> index 089e201d7550..22f2d4fd2577 100644
>> +++ b/drivers/infiniband/hw/hfi1/verbs.c
>> @@ -515,7 +515,7 @@ 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, lockdep_is_held(&(ibp->rvp.lock))) {
> 
> Okay, this looks reasonable
> 
> Mike, Dennis, is this the right lock to test?
> 

I'm looking at that right now actually, I don't think this is correct. 
Wanted to talk to Mike before I send a response though.

-Denny