Re: [PATCH] - Fix unmap_vma() bug related to mmu_notifiers

From: Andrea Arcangeli
Date: Mon Jan 25 2010 - 14:01:33 EST

On Mon, Jan 25, 2010 at 11:45:56AM -0600, Jack Steiner wrote:
> unmap_vmas() can fail to correctly flush the TLB if a
> callout to mmu_notifier_invalidate_range_start() sleeps.

Not sure I understand: the callbacks invoked by
mmu_notifier_invalidate_range_start can't sleep, or rcu locking inside
mmu notifier will break too (first thing that should be replaced with
srcu if they were allowed to sleep).

In short there's no schedule that could be added because of those
callbacks so if this code isn't ok and schedules and screw on the
mmu_gather tlb it's probably not mmu notifier related.
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