From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from he.sipsolutions.net ([78.46.109.217]:44300 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755072Ab2KNJOV (ORCPT ); Wed, 14 Nov 2012 04:14:21 -0500 Message-ID: <1352884491.9510.2.camel@jlt4.sipsolutions.net> (sfid-20121114_101439_085410_B4E4E8AA) Subject: Re: 'ip' blocking for long time trying to down station From: Johannes Berg To: Ben Greear Cc: "linux-wireless@vger.kernel.org" Date: Wed, 14 Nov 2012 10:14:51 +0100 In-Reply-To: <5091ADDD.4050407@candelatech.com> (sfid-20121101_000206_244719_62ADC7A2) References: <5091ADDD.4050407@candelatech.com> (sfid-20121101_000206_244719_62ADC7A2) Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Ben, Sorry for the late reply. > This is on the 400 station test machine. No more crashes, but I'm seeing long > pauses (10+ seconds) when trying to down station interfaces (and sometimes other > commands as well). The system cannot stabilize (my user-space app times out > after a while due to blocking on system() calls such as the one below, > and gives up, causing endless loops of up/down, associate, dhcp, etc) > I'm going to tweak the user-space code more to try to bring up stations > in smaller batches, but it still seems like there is room for improvement > in the OS. > > Using sysrq, I got this trace of the command. I'm not sure it was blocked > in the same place the whole time, but it seems likely. Any ideas for how > to speed this sort of thing up? > > ./local/sbin/ip link set sta140 down > > [] flush_work+0x2b/0x34 > [] ? cwq_dec_nr_in_flight+0x76/0x76 > [] ieee80211_do_stop+0x379/0x544 [mac80211] I'm guessing that the other interfaces are actually re-scheduling work items while this is trying to flush ... I'm not really sure how to improve this behaviour though. johannes