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Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

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On 09/27/2017 11:49 AM, Will Deacon wrote:

> The moral of the story is that read-after-read (same address) ordering *only*
> applies if READ_ONCE is used consistently. This means we need to fix page
> table dereferences in the core code as well as the arch code to avoid this
> problem. The two RFC patches in this series fix arm64 (which is a bigger fix
> that necessary since I clean things up too) and page_vma_mapped_walk.
> 
> Comments welcome.

Thanks for this Will. I'll echo Timur's comment that it would be ideal
to split this up into the critical piece needed for ordering
access/update to the PMD in the face of a THP split and separately have
the cosmetic cleanups. Needless to say, we've got a bunch of people who
are tracking this one and tracking it ready for backport. We just got
THP re-enabled so I'm pretty keen that we not have to disable again.

Jon.

-- 
Computer Architect | Sent from my Fedora powered laptop

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[RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes Will Deacon <will.deacon@arm.com> - 2017-09-27 18:00 +0200
  Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Peter Zijlstra <peterz@infradead.org> - 2017-09-28 10:40 +0200
    Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Will Deacon <will.deacon@arm.com> - 2017-09-28 10:50 +0200
      Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-28 17:50 +0200
        Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Will Deacon <will.deacon@arm.com> - 2017-09-28 17:50 +0200
          Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-28 18:10 +0200
        Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Michael Cree <mcree@orcon.net.nz> - 2017-09-28 21:40 +0200
          Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-29 03:00 +0200
            Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Will Deacon <will.deacon@arm.com> - 2017-09-29 11:10 +0200
              Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Will Deacon <will.deacon@arm.com> - 2017-09-29 18:40 +0200
              Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-09-29 18:40 +0200
  Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific  pgtable code leading to crashes Richard Ruigrok <rruigrok@codeaurora.org> - 2017-09-28 19:40 +0200
  Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when  accessing page tables Timur Tabi <timur@codeaurora.org> - 2017-09-28 21:20 +0200
  Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific  pgtable code leading to crashes Jon Masters <jcm@redhat.com> - 2017-09-28 21:40 +0200
    Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific  pgtable code leading to crashes Will Deacon <will.deacon@arm.com> - 2017-09-29 11:00 +0200

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