netdev - Re: [PATCH net-next] ath10k: fix RX of frames with broken FCS in monitor mode

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Date:   Thu, 7 Nov 2019 15:03:31 +0100
From:   Linus Lüssing <linus.luessing@...3.blue>
To:     Ben Greear <greearb@...delatech.com>
Cc:     Linus Lüssing <ll@...onwunderlich.de>,
        ath10k@...ts.infradead.org, Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] ath10k: fix RX of frames with broken FCS in
 monitor mode

On Tue, Nov 05, 2019 at 09:19:20AM -0800, Ben Greear wrote:
> Thanks for adding the counter.  Since it us u32, I doubt you need the spin lock
> below?

Ok, I can remove the spin-lock.

Just for clarification though, if I recall correctly then an increment operator
is not guaranteed to work atomically. But you think it's unlikely
to race with a concurrent ++ and therefore it's fine for just a debug counter?
(and if it were racing, it'd just be a missed +1)

Or is there another mechanism that avoids concurrency in the
ath10k RX path?


> 
> --Ben
> 
> > +	if (!(ar->filter_flags & FIF_FCSFAIL) &&
> > +	    status->flag & RX_FLAG_FAILED_FCS_CRC) {
> > +		spin_lock_bh(&ar->data_lock);
> > +		ar->stats.rx_crc_err_drop++;
> > +		spin_unlock_bh(&ar->data_lock);
> > +
> > +		dev_kfree_skb_any(skb);
> > +		return;
> > +	}
> > +
> >   	ath10k_dbg(ar, ATH10K_DBG_DATA,
> >   		   "rx skb %pK len %u peer %pM %s %s sn %u %s%s%s%s%s%s %srate_idx %u vht_nss %u freq %u band %u flag 0x%x fcs-err %i mic-err %i amsdu-more %i\n",
> >   		   skb,
> > 
> 
> 
> -- 
> Ben Greear <greearb@...delatech.com>
> Candela Technologies Inc  http://www.candelatech.com
>