From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: RT, what to do about up/down_read_non_owner() Date: Mon, 6 Jun 2016 20:24:46 +0100 Message-ID: <20160606192446.GE14480@ZenIV.linux.org.uk> References: <1465109869.4263.23.camel@gmail.com> <1465204028.11062.3.camel@gmail.com> <1465206604.6397.18.camel@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sebastian Andrzej Siewior , linux-rt-users , Thomas Gleixner , Peter Zijlstra , Ingo Molnar To: Mike Galbraith Return-path: Received: from zeniv.linux.org.uk ([195.92.253.2]:38636 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752095AbcFFTY4 (ORCPT ); Mon, 6 Jun 2016 15:24:56 -0400 Content-Disposition: inline In-Reply-To: <1465206604.6397.18.camel@gmail.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Mon, Jun 06, 2016 at 11:50:04AM +0200, Mike Galbraith wrote: > (CCs Al, who knows, maybe he'll make them go *poof*) > > > > > In v4.7, Al added those buggers to NFS. BCACHE is disabled in RT > > > > because of same.. but that's a somewhat suboptimal solution for > > > > something as widely used as NFS. > > > > > > > > Suggestions? I reverted the offending commit to get 4.7-rt up and > > > > running, but that's not gonna fly long term. > > > > > > This API should be avoided according to the comment and completions > > > should be used. I am for removal of those. Were the locking people okay > > > with this change in the first place or did this just sneak in? > > > > It just snuck in. Al reworked sillyunlink, whacking the wait_event() > > stuff that was there, using annoying $subject instead. It's more than just wait_event() crap being killed (and crap it certainly was). The situation is pretty much the same as with bcache; we don't want readers to stick around until the initiated action has been completed. What exactly is RT problem, just to be sure to avoid reproducing exact same issue in the replacement?