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Date: Wed, 23 Apr 2008 11:19:26 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: Andrea Arcangeli <andrea@qumranet.com>
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Subject: Re: [PATCH 01 of 12] Core of mmu notifiers
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On Wed, 23 Apr 2008, Andrea Arcangeli wrote:

> The only way to avoid failing because of vmalloc space shortage or
> oom, would be to provide a O(N*N) fallback. But one that can't be
> interrupted by sigkill! sigkill interruption was ok in #v12 because we
> didn't rely on mmu_notifier_unregister to succeed. So it avoided any
> DoS but it still can't provide any reliable unregister.

If unregister fails then the driver should not detach from the address
space immediately but wait until -->release is called. That may be
a possible solution. It will be rare that the unregister fails.