| Message ID | 20121203185838.E2A80100286@blech.mobile (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c index 6a86814..45c696b 100644 --- a/drivers/net/wireless/ath/carl9170/tx.c +++ b/drivers/net/wireless/ath/carl9170/tx.c @@ -1485,6 +1485,13 @@ void carl9170_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb) } if (info->flags & IEEE80211_TX_CTL_AMPDU) { + /* to static code analyzers and reviewers: + * mac80211 guarantees that a valid "sta" + * reference is present, if a frame is to + * be part of an ampdu. Hence any extra + * sta == NULL checks are redundant in this + * special case. + */ run = carl9170_tx_ampdu_queue(ar, sta, skb); if (run) carl9170_tx_ampdu(ar);
Dan Carpenter reported that smatch detected a potential problem with the code [1]: drivers/net/wireless/ath/carl9170/tx.c:1488 carl9170_op_tx() error: we previously assumed 'sta' could be null (see line 1482) drivers/net/wireless/ath/carl9170/tx.c 1482 if (sta) { ^^^^^ New check. [...] 1485 } 1487 if (info->flags & IEEE80211_TX_CTL_AMPDU) { 1488 run = carl9170_tx_ampdu_queue(ar, sta, skb); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Old dereference of "sta" inside the call to carl9170_tx_ampdu_queue(). A range of solutions have been discussed in [2] and we agreed on the following: " > 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." [1] <http://www.spinics.net/lists/linux-wireless/msg94526.html> [2] <http://www.spinics.net/lists/linux-kernel-janitors/msg14953.html> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Christian Lamparter <chunkeey@googlemail.com> --- drivers/net/wireless/ath/carl9170/tx.c | 7 +++++++ 1 file changed, 7 insertions(+)