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H A D | virtio_ring.c | diff 60f0779862e4ab943810187752c462e85f5fa371 Wed Jul 21 09:26:45 CDT 2021 Parav Pandit <parav@nvidia.com> virtio: Improve vq->broken access to avoid any compiler optimization
Currently vq->broken field is read by virtqueue_is_broken() in busy loop in one context by virtnet_send_command().
vq->broken is set to true in other process context by virtio_break_device(). Reader and writer are accessing it without any synchronization. This may lead to a compiler optimization which may result to optimize reading vq->broken only once.
Hence, force reading vq->broken on each invocation of virtqueue_is_broken() and also force writing it so that such update is visible to the readers.
It is a theoretical fix that isn't yet encountered in the field.
Signed-off-by: Parav Pandit <parav@nvidia.com> Link: https://lore.kernel.org/r/20210721142648.1525924-2-parav@nvidia.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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