Re: [PATCH] mm/mmap.c: Remove redundant vma looping

From	Andrea Arcangeli <aarcange@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm/mmap.c: Remove redundant vma looping
Date	2015-10-04 19:30 +0200
Message-ID	<qfVgK-6VO-9@gated-at.bofh.it> (permalink)
References	<qfAOZ-2Tr-3@gated-at.bofh.it> <qfBi2-3GQ-13@gated-at.bofh.it> <qfJyV-6Y7-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hello Chen,

On Sun, Oct 04, 2015 at 12:55:29PM +0800, Chen Gang wrote:
> Theoretically, the lock and unlock need to be symmetric, if we have to
> lock f_mapping all firstly, then lock all anon_vma, probably, we also
> need to unlock anon_vma all, then unlock all f_mapping.

They don't need to be symmetric because the unlocking order doesn't
matter. To avoid lock inversion deadlocks it is enough to enforce the
lock order.
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Thread

[PATCH] mm/mmap.c: Remove redundant vma looping Chen Gang <xili_gchen_5257@hotmail.com> - 2015-10-03 21:40 +0200
  Re: [PATCH] mm/mmap.c: Remove redundant vma looping Richard Weinberger <richard.weinberger@gmail.com> - 2015-10-03 22:10 +0200
    Re: [PATCH] mm/mmap.c: Remove redundant vma looping Chen Gang <xili_gchen_5257@hotmail.com> - 2015-10-04 07:00 +0200
      Re: [PATCH] mm/mmap.c: Remove redundant vma looping Andrea Arcangeli <aarcange@redhat.com> - 2015-10-04 19:30 +0200
        RE: [PATCH] mm/mmap.c: Remove redundant vma looping Chen Gang <xili_gchen_5257@hotmail.com> - 2015-10-05 14:30 +0200

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