Subject: Re: [PATCH 1/1] iwlwifi: rs: remove superfluous check

From: "Coelho, Luciano" <[email-masked]>
Date: Thu, 19 May 2016 08:27:13 +0000

On Wed, 2016-05-18 at 01:31 +0200, Heinrich Schuchardt wrote:
> If we dereference a variable anyway in other parts of the code,
> there is no need to check against NULL in a single place.

NACK.  This is not true.

If lq_sta is NULL, it means that mvm_sta is also NULL.  Then we call
the rate_control_send with mvm_sta == NULL:

	if (rate_control_send_low(sta, mvm_sta, txrc))
		return;

The rate_control_send_low() function looks like this:

bool rate_control_send_low(struct ieee80211_sta *pubsta,
			   void *priv_sta,
			   struct ieee80211_tx_rate_control *txrc)
{
[...]
	if (!pubsta || !priv_sta || rc_no_data_or_no_ack_use_min(txrc)) {
[...]
		return true;
	}
[...]
}

Which means that if priv_sta (aka mvm_sta) is NULL, we will return
without running the rest of rs_get_rate() where lq_sta is accessed
without checks.

I admit that the rs_get_rate() function is a bit hard to read, but
removing the lq_sta check as you did doesn't help, but makes things
worse.

--
Cheers,
Luca.