Messages in this thread | | | Date | Thu, 24 Nov 2016 22:36:58 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH 0/3] virtio/vringh: kill off ACCESS_ONCE() |
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On Thu, Nov 24, 2016 at 10:25:11AM +0000, Mark Rutland wrote: > For several reasons, it would be beneficial to kill off ACCESS_ONCE() > tree-wide, in favour of {READ,WRITE}_ONCE(). These work with aggregate types, > more obviously document their intended behaviour, and are necessary for tools > like KTSAN to work correctly (as otherwise reads and writes cannot be > instrumented separately). > > While it's possible to script the bulk of this tree-wide conversion, some cases > such as the virtio code, require some manual intervention. This series moves > the virtio and vringh code over to {READ,WRITE}_ONCE(), in the process fixing a > bug in the virtio headers. > > Thanks, > Mark.
I don't have a problem with this specific patchset.
Though I really question the whole _ONCE APIs esp with aggregate types - these seem to generate a memcpy and an 8-byte read/writes sometimes, and I'm pretty sure this simply can't be read/written at once on all architectures.
So I worry it's kind of like volatile in this respect, too easy to overuse.
> Mark Rutland (3): > tools/virtio: fix READ_ONCE() > vringh: kill off ACCESS_ONCE() > tools/virtio: use {READ,WRITE}_ONCE() in uaccess.h > > drivers/vhost/vringh.c | 5 +++-- > tools/virtio/linux/compiler.h | 2 +- > tools/virtio/linux/uaccess.h | 9 +++++---- > 3 files changed, 9 insertions(+), 7 deletions(-) > > -- > 2.7.4
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