netdev - RE: [PATCH net-next v3] Add support of Cavium Liquidio ethernet adapters

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Date:	Fri, 19 Dec 2014 22:39:47 +0000
From:	"Chickles, Derek" <Derek.Chickles@...iumnetworks.com>
To:	Lino Sanfilippo <LinoSanfilippo@....de>,
	"Vatsavayi, Raghu" <Raghu.Vatsavayi@...iumnetworks.com>,
	"davem@...emloft.net" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Burla, Satananda" <Satananda.Burla@...iumnetworks.com>,
	"Manlunas, Felix" <Felix.Manlunas@...iumnetworks.com>,
	"Vatsavayi, Raghu" <Raghu.Vatsavayi@...iumnetworks.com>
Subject: RE: [PATCH net-next v3] Add support of Cavium Liquidio ethernet
 adapters

> On 19.12.2014 04:25, Raghu Vatsavayi wrote:
> > +static int setup_nic_devices(struct octeon_device *octeon_dev)
> > +{
...
> > +
> > +	sc = kmalloc(sizeof(*sc), GFP_ATOMIC);
> > +	if (!sc)
> > +		return -ENOMEM;
> > +
> > +	resp = kmalloc(sizeof(*resp), GFP_KERNEL);
> > +	if (!resp) {
> > +		kfree(sc);
> > +		return -ENOMEM;
> > +	}
...
> > +		init_waitqueue_head(&resp->s.wc);
...
> > +
> > +		retval = octeon_send_soft_command(octeon_dev, sc);
> > +		if (retval) {
> > +			lio_dev_err(octeon_dev,
> > +				    "Link status instruction failed status: %x\n",
> > +				    retval);
> > +			/* Soft instr is freed by driver in case of failure. */
> > +			goto setup_nic_dev_fail;
> > +		}
> > +
> > +		/* Sleep on a wait queue till the cond flag indicates that the
> > +		 * response arrived or timed-out.
> > +		 */
> > +		sleep_cond(&resp->s.wc, &resp->s.cond);
...
> > +	kfree(sc);
> > +	kfree(resp);
> 
> I wonder if this is correct. AFAICS sc is the same memory that we put on
> the octeon_instr_queue (see send_soft_command() ->
> send_command()->add_to_nrlist()). Is that queue cleared before sc is
> freed?
> 
> 

Yes, it's correct. We wait for the response before exiting this loop with
that sleep_cond() call. This adds an entry to a wait_queue that is
serviced asynchronously and will return once it is complete.
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