From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756523AbdDFB3H (ORCPT ); Wed, 5 Apr 2017 21:29:07 -0400 Received: from mout.gmx.net ([212.227.17.22]:63037 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754505AbdDFB3A (ORCPT ); Wed, 5 Apr 2017 21:29:00 -0400 Message-ID: <1491442114.4718.35.camel@gmx.de> Subject: Re: net/sched: latent livelock in dev_deactivate_many() due to yield() usage From: Mike Galbraith To: Stephen Hemminger Cc: netdev , LKML , Peter Zijlstra Date: Thu, 06 Apr 2017 03:28:34 +0200 In-Reply-To: <20170405173105.7f41d7fc@plumbers-lap.home.lan> References: <1491107321.13631.33.camel@gmx.de> <20170405173105.7f41d7fc@plumbers-lap.home.lan> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:4w0Hzq82Y5xgmHbJodiPY5VGsm44UX5omkDHyzpsBZ25XMX5NWd mP0ZcXX1r5Mqk+6AWsTLcyKd7WI0w7VZ99/yQw8tcWOGhErGWD4lWFNyecD+ORUeD/KyXUe zS/ixb5qcNV6uM+P1vsMnWG6x/JZgAUUUlXxGVYUpsMxronahtNg5tI7Nb0Jg5eapoUNrXv u7+RFNALA2Z9L8setF9Jg== X-UI-Out-Filterresults: notjunk:1;V01:K0:ma/W8ao7+D4=:hXq1XmUr3hFa8fY4A6Xuxn VTHEvDZ2/vwrBmrJVxf0/YMX0fwR9E8kbwblICSHQCAaXWPOCgo8yPO/Wu69TRIFAK00py9be 63fhVyVt37aMHC/Q+0U8bpmo50PfFVIr+oZJPRMDrDAtnKNMu+j4+IUAVRtIcBo9M7VFdyVZI txHweLHBromM3PfaKulDZZsZC/J6Dvi4rGe0/Ugh6UHpVyIVqj2Ff7P8Mt3csZivRWpD12fOQ UXWKrF9lcjEj7ZnhLKIV5KmNVG7LtC8XD8z/ZZk6v6smCTyjTKAwJnBV93oY95lpotmdSa/ao NE5ajNvMgbN2FDvGoMoL/kXXQS5lYw5azUwm3ihydljZpYFwkNUjlCim2tiUcuFKX11N3dsk8 WHMyGkZFfyuIaNxILs9wa+HiHHHVDL29VYsjOkg9VT7/NMWp+NuHDpeobFAvDzeCR9h1Qjrtv +/T1PZ6A4XXXQuL+p/f5jUGcM/i51n2BX8VCut6/2cKz3rfS0g8g+Biou+T88hioh7DmoDl0E OiaDfiDcmhl1i1FnPYtV6Q7hxwolTetSyHFmO7sCPL1BYEVcqIVaeduhHtYVfcXh0nYPIuyhE tK9UgSBAcRFtbZRjJUTxYQZIlHUVArlmRNLOsjPKhO7zUjtPUaXjut1CBKykWS64Mrvb1fseb 7IkwML85eM2ar3hJ8eiXX787BKL7COHJbRT4z6R33lNyo89xXiRX4/0ZHjGDAi9eKugjN/J13 pYcq14GIKvKzFxhbRO1PyF0f0t+3O/2MUP89ohfe8Ws1I5admgHlJ0ur2a4NYYZ83chsEXIdW 1IoRC2h Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2017-04-05 at 17:31 -0700, Stephen Hemminger wrote: > On Sun, 02 Apr 2017 06:28:41 +0200 > Mike Galbraith wrote: > > > Livelock can be triggered by setting kworkers to SCHED_FIFO, then > > suspend/resume.. you come back from sleepy-land with a spinning > > kworker. For whatever reason, I can only do that with an enterprise > > like config, my standard config refuses to play, but no matter, it's > > "Typical broken usage". > > > > (yield() should be rendered dead) > > The kernel is not normally built to have kworkers run at SCHED_FIFO. > The user has do some action to alter the process priorities. > > I classify this as user error. We don't support killing kworker threads > either. We'll have to agree to disagree on that. I assert that any thread that must run as SCHED_OTHER in order to be safe is in fact broken. -Mike