linux-kernel - Re: [PATCH] mm/hmm: replace hmm_update with mmu_notifier

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Message-ID: <20190724180022.GD6410@dhcp22.suse.cz>
Date:   Wed, 24 Jul 2019 20:00:22 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        Ralph Campbell <rcampbell@...dia.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, nouveau@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH] mm/hmm: replace hmm_update with mmu_notifier_range

On Wed 24-07-19 17:33:05, Christoph Hellwig wrote:
> On Wed, Jul 24, 2019 at 12:28:58PM -0300, Jason Gunthorpe wrote:
> > Humm. Actually having looked this some more, I wonder if this is a
> > problem:
> 
> What a mess.
> 
> Question: do we even care for the non-blocking events?  The only place
> where mmu_notifier_invalidate_range_start_nonblock is called is the oom
> killer, which means the process is about to die and the pagetable will
> get torn down ASAP.  Should we just skip them unconditionally?

How do you tell whether they are going to block or not without trying?
-- 
Michal Hocko
SUSE Labs