From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 9DD6A6B2D6B for ; Fri, 23 Nov 2018 07:31:02 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id x15so5742667edd.2 for ; Fri, 23 Nov 2018 04:31:02 -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 n5-v6sor4075299ejs.35.2018.11.23.04.31.01 for (Google Transport Security); Fri, 23 Nov 2018 04:31:01 -0800 (PST) Date: Fri, 23 Nov 2018 13:30:57 +0100 From: Daniel Vetter Subject: Re: [PATCH 1/3] mm: Check if mmu notifier callbacks are allowed to fail Message-ID: <20181123123057.GK4266@phenom.ffwll.local> References: <20181122165106.18238-1-daniel.vetter@ffwll.ch> <20181122165106.18238-2-daniel.vetter@ffwll.ch> <20181123111557.GG8625@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181123111557.GG8625@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Daniel Vetter , LKML , Linux MM , Intel Graphics Development , DRI Development , Andrew Morton , Christian =?iso-8859-1?Q?K=F6nig?= , David Rientjes , =?iso-8859-1?B?Suly9G1l?= Glisse , Paolo Bonzini , Daniel Vetter 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. 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). Cheers, Daniel > > > Cc: Andrew Morton > > Cc: Michal Hocko > > Cc: "Christian K�nig" > > Cc: David Rientjes > > Cc: Daniel Vetter > > Cc: "J�r�me Glisse" > > Cc: linux-mm@kvack.org > > Cc: Paolo Bonzini > > Signed-off-by: Daniel Vetter > > --- > > mm/mmu_notifier.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c > > index 5119ff846769..59e102589a25 100644 > > --- a/mm/mmu_notifier.c > > +++ b/mm/mmu_notifier.c > > @@ -190,6 +190,8 @@ int __mmu_notifier_invalidate_range_start(struct mm_struct *mm, > > pr_info("%pS callback failed with %d in %sblockable context.\n", > > mn->ops->invalidate_range_start, _ret, > > !blockable ? "non-" : ""); > > + WARN(blockable,"%pS callback failure not allowed\n", > > + mn->ops->invalidate_range_start); > > ret = _ret; > > } > > } > > -- > > 2.19.1 > > > > -- > Michal Hocko > SUSE Labs -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch