linux-kernel - Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers

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Message-ID: <20180702115423.GK19043@dhcp22.suse.cz>
Date:   Mon, 2 Jul 2018 13:54:23 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Christian König <christian.koenig@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Sudeep Dutt <sudeep.dutt@...el.com>,
        Ashutosh Dixit <ashutosh.dixit@...el.com>,
        Dimitri Sivanich <sivanich@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>, kvm@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-mm@...ck.org,
        David Rientjes <rientjes@...gle.com>,
        Felix Kuehling <felix.kuehling@....com>
Subject: Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers

On Mon 02-07-18 11:14:58, Christian König wrote:
> Am 27.06.2018 um 09:44 schrieb Michal Hocko:
> > This is the v2 of RFC based on the feedback I've received so far. The
> > code even compiles as a bonus ;) I haven't runtime tested it yet, mostly
> > because I have no idea how.
> > 
> > Any further feedback is highly appreciated of course.
> 
> That sounds like it should work and at least the amdgpu changes now look
> good to me on first glance.
> 
> Can you split that up further in the usual way? E.g. adding the blockable
> flag in one patch and fixing all implementations of the MMU notifier in
> follow up patches.

But such a code would be broken, no? Ignoring the blockable state will
simply lead to lockups until the fixup parts get applied.
Is the split up really worth it? I was thinking about that but had hard
times to end up with something that would be bisectable. Well, except
for returning -EBUSY until all notifiers are implemented. Which I found
confusing.

> This way I'm pretty sure Felix and I can give an rb on the amdgpu/amdkfd
> changes.

If you are worried to give r-b only for those then this can be done even
for larger patches. Just make your Reviewd-by more specific
R-b: name # For BLA BLA
-- 
Michal Hocko
SUSE Labs