Re: [PATCH 3/5] track the root (oldest) anon_vma

[Rik van Riel]

On 05/12/2010 08:38 PM, KAMEZAWA Hiroyuki wrote:
> On Wed, 12 May 2010 13:39:58 -0400
> Rik van Riel<riel@xxxxxxxxxx>  wrote:
>
> > Subject: track the root (oldest) anon_vma
> >
> > Track the root (oldest) anon_vma in each anon_vma tree.   Because we only
> > take the lock on the root anon_vma, we cannot use the lock on higher-up
> > anon_vmas to lock anything.  This makes it impossible to do an indirect
> > lookup of the root anon_vma, since the data structures could go away from
> > under us.
> >
> > However, a direct pointer is safe because the root anon_vma is always the
> > last one that gets freed on munmap or exit, by virtue of the same_vma list
> > order and unlink_anon_vmas walking the list forward.
> >
> > Signed-off-by: Rik van Riel<riel@xxxxxxxxxx>
>
>
> Acked-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
>
> I welcome this. Thank you!
>
> Reading 4/5, I felt I'm grad if you add a Documentation or very-precise-comment
> about the new anon_vma rules and the _meaning_ of anon_vma_root_lock.
> I cannot fully convice myself that I understand them all.

Please send me a list of all the questions that come up
when you read the patches, and I'll prepare a patch 6/5
with just documentation :)

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