linux-kernel - Re: [PATCH v3 10/14] RDMA/ionic: Register device ops for control path

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Message-ID: <bb0ac425-2f01-b8c7-2fd7-4ecf9e9ef8b1@amd.com>
Date: Thu, 3 Jul 2025 12:49:30 +0530
From: Abhijit Gangurde <abhijit.gangurde@....com>
To: Leon Romanovsky <leon@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>
Cc: shannon.nelson@....com, brett.creeley@....com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, corbet@....net,
 andrew+netdev@...n.ch, allen.hubbe@....com, nikhil.agarwal@....com,
 linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Andrew Boyer <andrew.boyer@....com>
Subject: Re: [PATCH v3 10/14] RDMA/ionic: Register device ops for control path


On 7/2/25 23:30, Leon Romanovsky wrote:
> On Wed, Jul 02, 2025 at 10:18:03AM -0300, Jason Gunthorpe wrote:
>> On Tue, Jul 01, 2025 at 01:38:44PM +0300, Leon Romanovsky wrote:
>>>> +static void ionic_flush_qs(struct ionic_ibdev *dev)
>>>> +{
>>>> +	struct ionic_qp *qp, *qp_tmp;
>>>> +	struct ionic_cq *cq, *cq_tmp;
>>>> +	LIST_HEAD(flush_list);
>>>> +	unsigned long index;
>>>> +
>>>> +	/* Flush qp send and recv */
>>>> +	rcu_read_lock();
>>>> +	xa_for_each(&dev->qp_tbl, index, qp) {
>>>> +		kref_get(&qp->qp_kref);
>>>> +		list_add_tail(&qp->ibkill_flush_ent, &flush_list);
>>>> +	}
>>>> +	rcu_read_unlock();
>>> Same question as for CQ. What does RCU lock protect here?
>> It should protect the kref_get against free of qp. The qp memory must
>> be RCU freed.
> I'm not sure that this was intension here. Let's wait for an answer from the author.

As Jason mentioned, It was intended to protect the kref_get against free 
of cq and qp
in the destroy path.

>> But this pattern requires kref_get_unless_zero()
>>
>> Jason

I will change it for kref_get_unless_zero().

Thanks,
Abhijit