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

From	"Coelho, Luciano" <luciano.coelho@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/1] iwlwifi: rs: remove superfluous check
Date	2016-05-19 10:30 +0200
Message-ID	<rArvb-5HV-7@gated-at.bofh.it> (permalink)
References	<rzWKJ-2DG-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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.

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[PATCH 1/1] iwlwifi: rs: remove superfluous check Heinrich Schuchardt <xypron.glpk@gmx.de> - 2016-05-18 01:40 +0200
  Re: [PATCH 1/1] iwlwifi: rs: remove superfluous check "Coelho, Luciano" <luciano.coelho@intel.com> - 2016-05-19 10:30 +0200

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