diff options
| author | Christian Lamparter <chunkeey@googlemail.com> | 2012-12-03 21:48:05 +0400 |
|---|---|---|
| committer | John W. Linville <linville@tuxdriver.com> | 2012-12-06 23:58:55 +0400 |
| commit | 1981e881fd32160bf886a09b12794c640aafffb3 (patch) | |
| tree | 91ba694ec6b669f04088ae49a341bb8040244ff7 /drivers/net/wireless/ath/carl9170 | |
| parent | f241b244dd4703a560c74e2538f27fd466c8d41f (diff) | |
| download | linux-1981e881fd32160bf886a09b12794c640aafffb3.tar.xz | |
carl9170: explain why sta cannot be NULL for ampdus
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>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'drivers/net/wireless/ath/carl9170')
| -rw-r--r-- | drivers/net/wireless/ath/carl9170/tx.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c index 84377cf580e0..ef4ec0da6e49 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, } 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); |