Return-path: Received: from mail-pd0-f174.google.com ([209.85.192.174]:48603 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328Ab3K3Xsg (ORCPT ); Sat, 30 Nov 2013 18:48:36 -0500 Message-ID: <529A7955.9010507@gmail.com> (sfid-20131201_004915_582720_F0DC27FF) Date: Sun, 01 Dec 2013 07:48:37 +0800 From: Chen Gang MIME-Version: 1.0 To: Joe Perches CC: Johannes Berg , "John W. Linville" , rkuo , "linux-kernel@vger.kernel.org" , David Miller , linux-wireless@vger.kernel.org, netdev Subject: Re: [PATCH] net: mac80211: tx.c: be sure of 'sdata->vif.type' must be NL80211_IFTYPE_AP when be in NL80211_IFTYPE_AP case References: <528AEFB7.4060301@gmail.com> <20131125011938.GB18921@codeaurora.org> <5292B845.3010404@gmail.com> <5292B8A0.7020409@gmail.com> <5294255E.7040105@gmail.com> <52957ADA.2080704@gmail.com> (sfid-20131127_055211_558798_A7DF5684) <1385739487.8656.1.camel@jlt4.sipsolutions.net> <5299D306.7070701@gmail.com> (sfid-20131130_125901_519610_EDA4068E) <1385816013.4327.1.camel@jlt4.sipsolutions.net> <5299ED38.4090509@gmail.com> <5299EFDD.6060405@gmail.com> (sfid-20131130_150205_984535_068F14A9) <1385842134.6108.4.camel@jlt4.sipsolutions.net> <1385843940.2664.4.camel@joe-AO722> In-Reply-To: <1385843940.2664.4.camel@joe-AO722> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 12/01/2013 04:39 AM, Joe Perches wrote: > On Sat, 2013-11-30 at 21:08 +0100, Johannes Berg wrote: >> On Sat, 2013-11-30 at 22:02 +0800, Chen Gang wrote: >>> - fall-through is obvious (although I did not notice it, originally). >>> >>> - Check 'A' again just near by "case A" seems a little strange. >>> >>> - Some compilers aren't quit smart enough to know 'chanctx_conf' is OK. >> >> I know. If you have any good ideas of how to make it more obvious to the >> compiler, I'm all ears, I just don't like any of the solutions offered >> so far (and you aren't the first to do so either) :-) >> OK, thanks. >> FWIW, I find the label to be odd because if you're familiar with the >> code then AP/AP_VLAN *should* be identical except for two special things >> that are now linearly & neatly handled in the code (the first being the >> 4-addr station, the second the chanctx assignment which always has to be >> done regardless of 4-addr). IMHO the == check after case should be >> enough to make a human reader take a closer look. I understand that you >> didn't and that's OK since you were just trying to squelch compile >> warnings, but I don't see that this one warrants much attention. > > The label/test could be moved to save a couple of lines > of duplicated code. > Hmm... for me, it must be an implementation which can satisfy all of us. If ieee80211_subif_start_xmit() is not performance sensitive (I guess so), we can use some short static functions instead of some code blocks within ieee80211_subif_start_xmit(). - ieee80211_subif_start_xmit() is a long function (600+ lines). - use short static function can share some code. - if code can be shared, the work flow can be more clearer too (don't need fall-through or goto). And I guess, the implementation below can cause panic when "sdata->vif.type == NL80211_IFTYPE_AP_VLAN". :-( > Maybe: > > net/mac80211/tx.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) > > diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c > index 70b5a05..b2160f4 100644 > --- a/net/mac80211/tx.c > +++ b/net/mac80211/tx.c > @@ -1777,18 +1777,16 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb, > } > ap_sdata = container_of(sdata->bss, struct ieee80211_sub_if_data, > u.ap); > - chanctx_conf = rcu_dereference(ap_sdata->vif.chanctx_conf); > - if (!chanctx_conf) > - goto fail_rcu; > - band = chanctx_conf->def.chan->band; > - if (sta) > - break; > /* fall through */ > case NL80211_IFTYPE_AP: > - if (sdata->vif.type == NL80211_IFTYPE_AP) > - chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf); > + chanctx_conf = rcu_dereference(ap_sdata->vif.chanctx_conf); > if (!chanctx_conf) > goto fail_rcu; > + if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) { > + band = chanctx_conf->def.chan->band; > + if (sta) > + break; > + } > fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS); > /* DA BSSID SA */ > memcpy(hdr.addr1, skb->data, ETH_ALEN); > > -- Chen Gang