From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f70.google.com (mail-io1-f70.google.com [209.85.166.70]) by kanga.kvack.org (Postfix) with ESMTP id CB81A6B30EA for ; Fri, 23 Nov 2018 08:15:24 -0500 (EST) Received: by mail-io1-f70.google.com with SMTP id d63so11233455iog.4 for ; Fri, 23 Nov 2018 05:15:24 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id b8sor11123928itb.16.2018.11.23.05.15.23 for (Google Transport Security); Fri, 23 Nov 2018 05:15:23 -0800 (PST) MIME-Version: 1.0 References: <20181122165106.18238-1-daniel.vetter@ffwll.ch> <20181122165106.18238-2-daniel.vetter@ffwll.ch> <20181123111557.GG8625@dhcp22.suse.cz> <20181123123057.GK4266@phenom.ffwll.local> <20181123124358.GJ8625@dhcp22.suse.cz> In-Reply-To: <20181123124358.GJ8625@dhcp22.suse.cz> From: Daniel Vetter Date: Fri, 23 Nov 2018 14:15:11 +0100 Message-ID: Subject: Re: [PATCH 1/3] mm: Check if mmu notifier callbacks are allowed to fail Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Linux Kernel Mailing List , Linux MM , intel-gfx , dri-devel , Andrew Morton , =?UTF-8?Q?Christian_K=C3=B6nig?= , David Rientjes , Jerome Glisse , Paolo Bonzini , Daniel Vetter On Fri, Nov 23, 2018 at 1:43 PM Michal Hocko wrote: > On Fri 23-11-18 13:30:57, Daniel Vetter wrote: > > On Fri, Nov 23, 2018 at 12:15:57PM +0100, Michal Hocko wrote: > > > On Thu 22-11-18 17:51:04, Daniel Vetter wrote: > > > > Just a bit of paranoia, since if we start pushing this deep into > > > > callchains it's hard to spot all places where an mmu notifier > > > > implementation might fail when it's not allowed to. > > > > > > What does WARN give you more than the existing pr_info? Is really > > > backtrace that interesting? > > > > Automated tools have to ignore everything at info level (there's too much > > of that). I guess I could do something like > > > > if (blockable) > > pr_warn(...) > > else > > pr_info(...) > > > > WARN() is simply my goto tool for getting something at warning level > > dumped into dmesg. But I think the pr_warn with the callback function > > should be enough indeed. > > I wouldn't mind s@pr_info@pr_warn@ Well that's too much, because then it would misfire in the oom testcase, where failing is ok (desireble even, we want to avoid blocking after all). So needs to be a switch (or else we need to filter it in results, and that's a bit a maintenance headache from a CI pov). -Danile > > If you wonder where all the info level stuff happens that we have to > > ignore: suspend/resume is a primary culprit (fairly important for > > gfx/desktops), but there's a bunch of other places. Even if we ignore > > everything at info and below we still need filters because some drivers > > are a bit too trigger-happy (i915 definitely included I guess, so everyone > > contributes to this problem). > > Thanks for the clarification. > -- > Michal Hocko > SUSE Labs -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch