Re: [dpdk-dev] [PATCH] kni: add support for core_id param in single threaded mode

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 21 Sep 2016 19:23:47 +0100
Ferruh Yigit <ferruh.yigit@intel.com> wrote:

> On 9/21/2016 6:15 PM, Vladyslav Buslov wrote:
> >> On 9/20/2016 7:36 PM, Stephen Hemminger wrote:  
> >>> On Tue, 20 Sep 2016 21:16:37 +0300
> >>> Vladyslav Buslov <vladyslav.buslov@harmonicinc.com> wrote:
> >>>  
> >>>> @@ -123,6 +125,9 @@ static int __net_init kni_init_net(struct net *net)
> >>>>  	/* Clear the bit of device in use */
> >>>>  	clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
> >>>>
> >>>> +	mutex_init(&knet->kni_kthread_lock);
> >>>> +	knet->kni_kthread = NULL;
> >>>> +  
> >>>
> >>> Why not just use kzalloc() here? You would still need to init the
> >>> mutex etc, but it would be safer.
> >>>  
> >>
> >> Hi Vladyslav,
> >>
> >> This is good suggestion, if you send a new version for this update, please
> >> keep my Ack.
> >>
> >> Thanks,
> >> ferruh  
> > 
> > Hi Ferruh, Stephen,
> > 
> > Could you please elaborate on using kzalloc for this code.
> > Currently kni_thread_lock is value member of kni_net structure and never explicitly allocated or deallocated.
> > Kni_kthread is pointer member of kni_net and is implicitly created and destroyed by kthread_run, kthread_stop functions.
> > Which one of those do you suggest to allocate with kzalloc() and how would it improve safety?
> >   
> 
> Currently:
> 
> kni_init_net() {
>     knet = kmalloc(..);
>     ..
>     mutex_init(..);
>     knet->kni_thread = NULL;
> }
> 
> If you allocate knet via kzalloc(), no need to assign NULL to
> kni_thread. Also this is safer because any uninitialized knet field will
> be zero instead of random value.
> 
> This is what I understood at least J

Also any additional fields in knet will be set, avoiding any present
or future uninitialized memory bugs.