Re: [PATCH] mm: protect against concurrent vma expansion

From: Michel Lespinasse
Date: Wed Dec 19 2012 - 22:07:13 EST

Hi Simon,

On Wed, Dec 19, 2012 at 5:56 PM, Simon Jeons <simon.jeons@xxxxxxxxx> wrote:
> One question.
> I found that mainly callsite of expand_stack() is #PF, but it holds
> mmap_sem each time before call expand_stack(), how can hold a *shared*
> mmap_sem happen?

the #PF handler calls down_read(&mm->mmap_sem) before calling expand_stack.

I think I'm just confusing you with my terminology; shared lock ==
read lock == several readers might hold it at once (I'd say they share

Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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