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Date: Thu, 22 Oct 2015 17:15:09 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, qemu-devel@nongnu.org, kvm@vger.kernel.org,
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Subject: Re: [PATCH 14/23] userfaultfd: wake pending userfaults
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On Thu, Oct 22, 2015 at 04:18:31PM +0200, Andrea Arcangeli wrote:

> The risk of memory corruption is still zero no matter what happens
> here, in the extremely rare case the app will get a SIGBUS or a

That might still upset people, SIGBUS isn't something an app can really
recover from.

> I'm not exactly sure why we allow VM_FAULT_RETRY only once currently
> so I'm tempted to drop FAULT_FLAG_TRIED entirely.

I think to ensure we make forward progress.

> I've no real preference on how to tweak the page fault code to be able
> to return VM_FAULT_RETRY indefinitely and I would aim for the smallest
> change possible, so if you've suggestions now it's good time.

Indefinitely is such a long time, we should try and finish
computation before the computer dies etc. :-)

Yes, yes.. I know, extremely unlikely etc. Still guarantees are good.


In any case, I'm not really too bothered how you fix it, just figured
I'd let you know.