Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount

From	Christoph Hellwig <hch@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount
Date	2016-10-17 11:40 +0200
Message-ID	<stcyK-1Fs-21@gated-at.bofh.it> (permalink)
References	<ssMXD-22Y-3@gated-at.bofh.it> <st1N0-3dc-33@gated-at.bofh.it> <st2zn-3wB-5@gated-at.bofh.it>
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On Sun, Oct 16, 2016 at 03:48:42PM -0700, Joel Fernandes wrote:
> Also, one more thing about the barrier dances you mentioned, this will
> also be done by the spinlock which was there before my patch. So in
> favor of my patch, it doesn't make things any worse than they were and
> actually fixes the reported issue while preserving the original code
> behavior. So I think it is a good thing to fix the issue considering
> so many people are reporting it and any clean ups of the vmalloc code
> itself can follow.

I'm not worried about having barriers, we use them all over our
synchronization primitives.  I'm worried about opencoding them
instead of having them in these well defined helpers.

So based on this discussion and the feedback from Nick I'll
propose a new patch (or rather a series to make it more understandable)
that adds a mutex, adds the lockbreak and gives sensible calling
conventions to __purge_vmap_area_lazy.

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[PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount Joel Fernandes <joelaf@google.com> - 2016-10-15 15:00 +0200
  Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic  refcount Christoph Hellwig <hch@infradead.org> - 2016-10-15 18:50 +0200
    Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic  refcount Christoph Hellwig <hch@infradead.org> - 2016-10-15 19:00 +0200
      Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount Joel Fernandes <joelaf@google.com> - 2016-10-16 01:10 +0200
        Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic  refcount Christoph Hellwig <hch@infradead.org> - 2016-10-16 08:20 +0200
          Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount Joel Fernandes <joelaf@google.com> - 2016-10-17 00:10 +0200
            Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic refcount Joel Fernandes <joelaf@google.com> - 2016-10-17 01:00 +0200
              Re: [PATCH v3] mm: vmalloc: Replace purge_lock spinlock with atomic  refcount Christoph Hellwig <hch@infradead.org> - 2016-10-17 11:40 +0200

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