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Commit d307fb16 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
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Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" 



This reverts commit 9e1a27ea.

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: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 6a65d263

include/linux/virtio_ring.h

+19 −4
Original line number Diff line number Diff line
@@ -21,20 +21,19 @@ 
 * actually quite cheap.

 */



#ifdef CONFIG_SMP

static inline void virtio_mb(bool weak_barriers)

{

#ifdef CONFIG_SMP

	if (weak_barriers)

		smp_mb();

	else

#endif

		mb();

}



static inline void virtio_rmb(bool weak_barriers)

{

	if (weak_barriers)

		dma_rmb();

		smp_rmb();

	else

		rmb();

}
@@ -42,10 +41,26 @@ static inline void virtio_rmb(bool weak_barriers) 
static inline void virtio_wmb(bool weak_barriers)

{

	if (weak_barriers)

		dma_wmb();

		smp_wmb();

	else

		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 virtqueue;