linux-kernel - Re: Re: [PATCH v1 2/2] hamradio: defer 6pack kfree after unregister

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Date:   Thu, 11 Nov 2021 10:09:59 +0800 (GMT+08:00)
From:   "Lin Ma" <linma@....edu.cn>
To:     "Jakub Kicinski" <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jirislaby@...nel.org,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v1 2/2] hamradio: defer 6pack kfree after
 unregister_netdev

Hi there,

> Sent Time: 2021-11-11 10:06:12 (Thursday)
> To: "Lin Ma" <linma@....edu.cn>
> Cc: netdev@...r.kernel.org, davem@...emloft.net, jirislaby@...nel.org, gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v1 2/2] hamradio: defer 6pack kfree after unregister_netdev
> 
> On Wed, 10 Nov 2021 18:05:25 -0800 Jakub Kicinski wrote:
> > > diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
> > > index 49f10053a794..bfdf89e54752 100644
> > > --- a/drivers/net/hamradio/6pack.c
> > > +++ b/drivers/net/hamradio/6pack.c
> > > @@ -672,11 +672,13 @@ static void sixpack_close(struct tty_struct *tty)
> > >  	del_timer_sync(&sp->tx_t);
> > >  	del_timer_sync(&sp->resync_t);
> > >  
> > > -	/* Free all 6pack frame buffers. */
> > > +	unregister_netdev(sp->dev);
> > > +
> > > +	/* Free all 6pack frame buffers after unreg. */
> > >  	kfree(sp->rbuff);
> > >  	kfree(sp->xbuff);
> > >  
> > > -	unregister_netdev(sp->dev);
> > > +	free_netdev(sp->dev);  
> > 
> > You should mention in the commit message why you think it's safe to add
> > free_netdev() which wasn't here before...
> > 
> > This driver seems to be setting:
> > 
> > 	dev->needs_free_netdev	= true;
> > 
> > so unregister_netdev() will free the netdev automatically.
> > 
> > That said I don't see a reason why this driver needs the automatic
> > cleanup.
> > 
> > You can either remove that setting and then you can call free_netdev()
> > like you do, or you need to move the cleanup to dev->priv_destructor.
> 
> Looks like this go applied already, please send a follow up fix.

Oooops, thanks for the remind. XD

I just found that the mkill adds the free_netdev after the unregister_netdev so I did it too. No idea about this automatic cleanup.

Should I send the fix in this thread or open a new one?

Thanks

Lin