From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-gy0-f174.google.com ([209.85.160.174]:39429 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751318Ab0KAQju convert rfc822-to-8bit (ORCPT ); Mon, 1 Nov 2010 12:39:50 -0400 Received: by gyg4 with SMTP id 4so3292175gyg.19 for ; Mon, 01 Nov 2010 09:39:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <8762whrqvm.fsf@gmail.com> References: <8762whrqvm.fsf@gmail.com> Date: Mon, 1 Nov 2010 17:39:49 +0100 Message-ID: Subject: Re: [ath9k-devel] ath9k: race conditions in dma From: =?ISO-8859-1?Q?Bj=F6rn_Smedman?= To: Ben Gamari Cc: linux-wireless , ath9k-devel@lists.ath9k.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, Nov 1, 2010 at 4:43 PM, Ben Gamari wrote: > On Mon, 1 Nov 2010 16:17:23 +0100, Björn Smedman wrote: >> Hi all, >> >> I have an application that creates and destroys a lot of ap vifs and >> does a lot of monitor frame injection. The recent ath9k rx locking >> fixes have helped with stability in this use-case but there still >> seems to be some tx/beacon related race condition(s). These manifests >> themselves as follows on an AR913x based router running >> compat-wireless-2010-10-19 (with locking fixes etc from openwrt): >> >> 1. TX DMA hangs under simultaneous high RX and TX load >> 2. TX is completely hung but chip is never reset > > I have also observed both of these behaviors with just a standard > hostapd single VIF configuration. Quite annoying. It seems to be better > with recent wireless-testing trees. > > - Ben The next thing that looks racy to me is ath_beacon_alloc() vs ath_beacon_tasklet() in beacon.c. Beacon queue TX DMA is always stopped in main.c before calling ath_beacon_alloc() but ath_beacon_tasklet() is scheduled when we get an SWBA interrupt. My guess is that these keep coming even if we stop TX DMA on the beacon queue, no? /Björn From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Bj=F6rn_Smedman?= Date: Mon, 1 Nov 2010 17:39:49 +0100 Subject: [ath9k-devel] ath9k: race conditions in dma In-Reply-To: <8762whrqvm.fsf@gmail.com> References: <8762whrqvm.fsf@gmail.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ath9k-devel@lists.ath9k.org On Mon, Nov 1, 2010 at 4:43 PM, Ben Gamari wrote: > On Mon, 1 Nov 2010 16:17:23 +0100, Bj?rn Smedman wrote: >> Hi all, >> >> I have an application that creates and destroys a lot of ap vifs and >> does a lot of monitor frame injection. The recent ath9k rx locking >> fixes have helped with stability in this use-case but there still >> seems to be some tx/beacon related race condition(s). These manifests >> themselves as follows on an AR913x based router running >> compat-wireless-2010-10-19 (with locking fixes etc from openwrt): >> >> 1. TX DMA hangs under simultaneous high RX and TX load >> 2. TX is completely hung but chip is never reset > > I have also observed both of these behaviors with just a standard > hostapd single VIF configuration. Quite annoying. It seems to be better > with recent wireless-testing trees. > > - Ben The next thing that looks racy to me is ath_beacon_alloc() vs ath_beacon_tasklet() in beacon.c. Beacon queue TX DMA is always stopped in main.c before calling ath_beacon_alloc() but ath_beacon_tasklet() is scheduled when we get an SWBA interrupt. My guess is that these keep coming even if we stop TX DMA on the beacon queue, no? /Bj?rn