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Subject: Re: [PATCH 1/3] infiniband: hw: hfi1: verbs.c: Use built-in RCU list
 checking
To:     Jason Gunthorpe <jgg@ziepe.ca>, madhuparnabhowmik04@gmail.com
Cc:     mike.marciniszyn@intel.com, paulmck@kernel.org,
        joel@joelfernandes.org, frextrite@gmail.com,
        linux-kernel-mentees@lists.linuxfoundation.org,
        rcu@vger.kernel.org, linux-rdma@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200114162345.19995-1-madhuparnabhowmik04@gmail.com>
 <20200114165740.GB22037@ziepe.ca>
From:   Dennis Dalessandro <dennis.dalessandro@intel.com>
Message-ID: <74adec84-ec5b-ea1b-7adf-3f8608838259@intel.com>
Date:   Tue, 14 Jan 2020 12:00:19 -0500
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On 1/14/2020 11:57 AM, Jason Gunthorpe wrote:
> On Tue, Jan 14, 2020 at 09:53:45PM +0530, madhuparnabhowmik04@gmail.com wrote:
>> From: Madhuparna Bhowmik <madhuparnabhowmik04@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@gmail.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