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Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb"

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This reverts commit 9e1a27ea42.

While that commit optimizes !CONFIG_SMP, it mixes
up DMA and SMP concepts, making the code hard
to figure out.

A better way to optimize this is with the new __smp_XXX
barriers.

As a first step, go back to full rmb/wmb barriers
for !SMP.
We switch to __smp_XXX barriers in the next patch.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
Michael S. Tsirkin 2015-12-20 13:52:10 +02:00
parent 6a65d26385
commit d307fb16f7
1 changed files with 19 additions and 4 deletions
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23
include/linux/virtio_ring.h
View file

@ -21,20 +21,19 @@
* actually quite cheap. * actually quite cheap.
*/ */
#ifdef CONFIG_SMP
static inline void virtio_mb(bool weak_barriers) static inline void virtio_mb(bool weak_barriers)
{ {
#ifdef CONFIG_SMP
if (weak_barriers) if (weak_barriers)
smp_mb(); smp_mb();
else else
#endif
mb(); mb();
} }
static inline void virtio_rmb(bool weak_barriers) static inline void virtio_rmb(bool weak_barriers)
{ {
if (weak_barriers) if (weak_barriers)
dma_rmb(); smp_rmb();
else else
rmb(); rmb();
} }
@ -42,10 +41,26 @@ static inline void virtio_rmb(bool weak_barriers)
static inline void virtio_wmb(bool weak_barriers) static inline void virtio_wmb(bool weak_barriers)
{ {
if (weak_barriers) if (weak_barriers)
dma_wmb(); smp_wmb();
else else
wmb(); wmb();
} }
#else
static inline void virtio_mb(bool weak_barriers)
{
mb();
}
static inline void virtio_rmb(bool weak_barriers)
{
rmb();
}
static inline void virtio_wmb(bool weak_barriers)
{
wmb();
}
#endif
struct virtio_device; struct virtio_device;
struct virtqueue; struct virtqueue;