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Groups > linux.kernel > #1530399

Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE()

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE()
Date 2016-11-25 17:20 +0100
Message-ID <sHroe-2Rp-7@gated-at.bofh.it> (permalink)
References (5 earlier) <sHo6Z-CC-5@gated-at.bofh.it> <sHo70-CC-41@gated-at.bofh.it> <sHq8N-1SA-9@gated-at.bofh.it> <sHqBQ-2hw-29@gated-at.bofh.it> <sHroe-2Rp-5@gated-at.bofh.it>
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On Fri, Nov 25, 2016 at 04:10:04PM +0000, Mark Rutland wrote:
> On Fri, Nov 25, 2016 at 04:21:39PM +0100, Dmitry Vyukov wrote:

> > What are use cases for such primitive that won't be OK with "read once
> > _and_ atomically"?
> 
> I have none to hand.

Whatever triggers the __builtin_memcpy() paths, and even the size==8
paths on 32bit.

You could put a WARN in there to easily find them.

The advantage of introducing the SINGLE_{LOAD,STORE}() helpers is that
they compiletime validate this the size is 'right' and can runtime check
alignment constraints.

IE, they are strictly stronger than {READ,WRITE}_ONCE().

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Thread

[PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-24 11:30 +0100
  [PATCH 2/3] vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-24 11:30 +0100
    Re: [PATCH 2/3] vringh: kill off ACCESS_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-11-24 12:20 +0100
    Re: [PATCH 2/3] vringh: kill off ACCESS_ONCE() Cornelia Huck <cornelia.huck@de.ibm.com> - 2016-11-24 12:40 +0100
    Re: [PATCH 2/3] vringh: kill off ACCESS_ONCE() Jason Wang <jasowang@redhat.com> - 2016-11-25 03:50 +0100
  [PATCH 1/3] tools/virtio: fix READ_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-24 11:30 +0100
    Re: [PATCH 1/3] tools/virtio: fix READ_ONCE() Cornelia Huck <cornelia.huck@de.ibm.com> - 2016-11-24 12:40 +0100
    Re: [PATCH 1/3] tools/virtio: fix READ_ONCE() Jason Wang <jasowang@redhat.com> - 2016-11-25 03:40 +0100
  [PATCH 3/3] tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h Mark Rutland <mark.rutland@arm.com> - 2016-11-24 11:30 +0100
    Re: [PATCH 3/3] tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h Cornelia Huck <cornelia.huck@de.ibm.com> - 2016-11-24 12:40 +0100
    Re: [PATCH 3/3] tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h Jason Wang <jasowang@redhat.com> - 2016-11-25 03:50 +0100
  Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-24 21:40 +0100
    Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 12:30 +0100
      Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-11-25 12:40 +0100
        Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 13:30 +0100
          Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Peter Zijlstra <peterz@infradead.org> - 2016-11-25 13:50 +0100
            Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Peter Zijlstra <peterz@infradead.org> - 2016-11-25 13:50 +0100
              Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Boqun Feng <boqun.feng@gmail.com> - 2016-11-25 16:00 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Dmitry Vyukov <dvyukov@google.com> - 2016-11-25 16:30 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 17:20 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Peter Zijlstra <peterz@infradead.org> - 2016-11-25 17:20 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 17:40 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-11-25 18:00 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 18:30 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Peter Zijlstra <peterz@infradead.org> - 2016-11-25 18:50 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-11-25 19:50 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-25 22:10 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-11-25 22:50 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Dmitry Vyukov <dvyukov@google.com> - 2016-11-25 18:30 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 18:50 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Linus Torvalds <torvalds@linux-foundation.org> - 2016-11-25 19:00 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 19:10 +0100
                Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Linus Torvalds <torvalds@linux-foundation.org> - 2016-11-25 19:50 +0100
            Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() Mark Rutland <mark.rutland@arm.com> - 2016-11-25 15:40 +0100

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