Return-path: Received: from mail-bk0-f42.google.com ([209.85.214.42]:63200 "EHLO mail-bk0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751947AbaATPlX convert rfc822-to-8bit (ORCPT ); Mon, 20 Jan 2014 10:41:23 -0500 Received: by mail-bk0-f42.google.com with SMTP id 6so448471bkj.15 for ; Mon, 20 Jan 2014 07:41:21 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1390227670-19030-6-git-send-email-michal.kazior@tieto.com> References: <1390227670-19030-1-git-send-email-michal.kazior@tieto.com> <1390227670-19030-6-git-send-email-michal.kazior@tieto.com> Date: Mon, 20 Jan 2014 16:41:21 +0100 Message-ID: (sfid-20140120_164129_803443_751F43FF) Subject: Re: [PATCH 5/7] mac80211: improve CSA locking From: Michal Kazior To: linux-wireless Cc: Johannes Berg , Michal Kazior Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 20 January 2014 15:21, Michal Kazior wrote: > The patch improves channel switch related locking > (STA, IBSS, AP, mesh). > > Now read access to sdata->vif.csa_active is > protected by wdev.mtx and local->mtx so holding > either is enough for read access but both are > required for write access. Keep in mind sdata lock > must be taken before local->mtx. Taking them in > reverse order creates a deadlock situation. > > The only exception is ieee80211_beacon_get_tim() > but it's safe to leave it as is and it doesn't > influence mac80211 state in any way. > > The patch adds a few lockdep assertions along for > easier code/locking maintenance. > > This also prepares for multi-interface CSA. > > Signed-off-by: Michal Kazior > --- > net/mac80211/cfg.c | 22 +++++++++++++++++++--- > net/mac80211/ibss.c | 18 ++++++++++++++---- > net/mac80211/iface.c | 28 ++++++++++++++++++++++++++-- > net/mac80211/mesh.c | 18 ++++++++++++++++-- > net/mac80211/mlme.c | 20 ++++++++++++++------ > 5 files changed, 89 insertions(+), 17 deletions(-) > [..] > diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c > index bfb81cb..d898dc9 100644 > --- a/net/mac80211/mlme.c > +++ b/net/mac80211/mlme.c > @@ -1987,10 +1988,9 @@ static void __ieee80211_disconnect(struct ieee80211_sub_if_data *sdata) > u8 frame_buf[IEEE80211_DEAUTH_FRAME_LEN]; > > sdata_lock(sdata); > - if (!ifmgd->associated) { > - sdata_unlock(sdata); > - return; > - } > + mutex_lock(&sdata->local->mtx); > + if (!ifmgd->associated) > + goto out; > > ieee80211_set_disassoc(sdata, IEEE80211_STYPE_DEAUTH, > WLAN_REASON_DISASSOC_DUE_TO_INACTIVITY, Just noticed ths deadlocks STA CSA failpath. This deadlocks with ieee80211_set_disassoc() -> ieee80211_stop_poll() and mutex around ieee80211_vif_release_channel(). I suppose s/ieee80211_stop_poll/__ieee80211_stop/ and removing explicit local->mtx lock around ieee80211_vif_relase_channel() should be enough. Michał