| Message ID | 201212022124.53838.chunkeey@googlemail.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Sun, Dec 02, 2012 at 09:24:53PM +0100, Christian Lamparter wrote: > On Sunday, December 02, 2012 05:51:53 PM Dan Carpenter wrote: > > On Sun, Dec 02, 2012 at 02:49:20PM +0100, Christian Lamparter wrote: > > > On Sunday 02 December 2012 11:42:38 Dan Carpenter wrote: > > > > The "sta" variable is not checked for NULL consistently and it makes the > > > > static checkers complain. I asked Christian Lamparter about this and > > > > it turns out the check is not needed. "In fact, in order to set up a > > > > ampdu session, the stack would call the driver's op_ampdu_action > > > > callback which always needs a station." > > > > > > that would be from the thread: > > > <http://www.spinics.net/lists/linux-wireless/msg94526.html> > > > > > > > I have removed the check. > > > I think this will bug for multicast and injected frames. > > > > > > It is not possible for the sta(tion) pointer to be NULL if > > > the frame has the IEEE80211_TX_CTL_AMPDU flag set. So the > > > sta == NULL check can be avoided when calling > > > carl9170_tx_ampdu_queue. This is because mac80211 tracks > > > all aggregation sessions within the station struct. > > > Of course, this is something that the checker tool can't > > > possibly deduce, but it has a point and we can add a check > > > like this [see attached draft patch]: > > > > > > What do you think [or more to the point: what does the > > > checker say?] > > > > > > > So we wouldn't apply my patch, we would apply that one instead? > We could, but that's up for debate (no, I don't think we are done > just yet). > > > I think that's great. My static checker doesn't understand bit > > flags yet so it would complain but it would be obvious to a human > > reader. > then we might as well add a comment to carl9170_tx_ampdu_queue > and explain the situation [in a way that's obvious to a > human reader]. This way we can save the "if"... which is a small > win since carl9170_op_tx is sort of a hot-path. > Putting a comment there is fine. Without the comment it's easy for a human reader to get confused why the check is there. So long as humans can read the code, that's all that matters. > > Could you just resend that patch with a signed-off-by? > Once we know what to do... yes :) > I have attached another patch. With this patch the checker > should be able to read the code without throwing any > warnings. Heh. You have a lot of faith in checker's ability to read code. In theory you are right, but it turns out that Smatch is ignoring the stuff inside the WARN_ON_ONCE(). It's not supposed to do that in this case; it should only do that if the WARN_ON_ONCE() is in a statement by itself. I'll take a look at this, but not tonight. Anyway, do whatever you think is best. I just misunderstood what you said earlier about it not being possible to be NULL. I understand it better now I think. Thanks. regards, dan carpenter -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c index 84377cf..6c83328 100644 --- a/drivers/net/wireless/ath/carl9170/tx.c +++ b/drivers/net/wireless/ath/carl9170/tx.c @@ -1463,13 +1463,16 @@ void carl9170_op_tx(struct ieee80211_hw *hw, struct ar9170 *ar = hw->priv; struct ieee80211_tx_info *info; struct ieee80211_sta *sta = control->sta; - bool run; + bool run, aggr; if (unlikely(!IS_STARTED(ar))) goto err_free; info = IEEE80211_SKB_CB(skb); + aggr = !!(info->flags & IEEE80211_TX_CTL_AMPDU) && + !WARN_ON_ONCE(!sta); + if (unlikely(carl9170_tx_prepare(ar, sta, skb))) goto err_free; @@ -1484,7 +1487,7 @@ void carl9170_op_tx(struct ieee80211_hw *hw, atomic_inc(&stai->pending_frames); } - if (info->flags & IEEE80211_TX_CTL_AMPDU) { + if (aggr) { run = carl9170_tx_ampdu_queue(ar, sta, skb); if (run) carl9170_tx_ampdu(ar);