From patchwork Thu Nov 21 17:19:52 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Simon Wunderlich X-Patchwork-Id: 3219991 Return-Path: X-Original-To: patchwork-linux-wireless@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id A6406C045B for ; Thu, 21 Nov 2013 17:20:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7750F20780 for ; Thu, 21 Nov 2013 17:20:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A4BFE20789 for ; Thu, 21 Nov 2013 17:20:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754806Ab3KURUo (ORCPT ); Thu, 21 Nov 2013 12:20:44 -0500 Received: from packetmixer.de ([79.140.42.25]:56020 "EHLO mail.mail.packetmixer.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754784Ab3KURUn (ORCPT ); Thu, 21 Nov 2013 12:20:43 -0500 Received: from kero.packetmixer.de (drsd-4dbdbb45.pool.mediaWays.net [77.189.187.69]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mail.mail.packetmixer.de (Postfix) with ESMTPSA id 284AD62402; Thu, 21 Nov 2013 17:32:42 +0000 (UTC) From: Simon Wunderlich To: johannes@sipsolutions.net Cc: linux-wireless@vger.kernel.org, Simon Wunderlich Subject: [PATCHv2 4/5] mac80211: don't cancel csa finalize work within stop_ap Date: Thu, 21 Nov 2013 18:19:52 +0100 Message-Id: <1385054393-17238-5-git-send-email-sw@simonwunderlich.de> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1385054393-17238-1-git-send-email-sw@simonwunderlich.de> References: <1385054393-17238-1-git-send-email-sw@simonwunderlich.de> Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The current channel switch code has a potential deadlock: 1) * cfg80211_stop_ap acquires wdev-lock * ieee80211_stop_ap calls cancel_work_sync for the csa_finalize_work, which acquires the associated worker-lock 2) * ieee80211_csa_finalize_work holds the worker-lock when run * it calls cfg80211_ch_switch_notify which will claim the wdev-lock, and also needs to claim the sdata-lock (which is the same as the wdev-lock) to modify the beacons. It is sufficient to just set the channel switch active to false. If the worker is running later, it will find the channel switch to not be active anymore and returns immediately without changing anything. Canceling the worker is done anyway when the interface goes down (ieee80211_do_stop). Reported-by: Johannes Berg Signed-off-by: Simon Wunderlich --- net/mac80211/cfg.c | 1 - 1 file changed, 1 deletion(-) diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index a135e6f..9f19cde 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -1080,7 +1080,6 @@ static int ieee80211_stop_ap(struct wiphy *wiphy, struct net_device *dev) /* abort any running channel switch */ sdata->vif.csa_active = false; - cancel_work_sync(&sdata->csa_finalize_work); cancel_work_sync(&sdata->u.ap.request_smps_work); /* turn off carrier for this interface and dependent VLANs */