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| author | Michael S. Tsirkin <mst@redhat.com> | 2015-12-20 13:52:10 +0200 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2016-01-12 20:47:00 +0200 |
| commit | d307fb16f788823b29aab9aa7e4821ac8a124b19 (patch) | |
| tree | 62a988d99febab95f276b807f365d1b4abbd90e9 /include/linux/virtio_ring.h | |
| parent | 6a65d26385bf487926a0616650927303058551e3 (diff) | |
| download | lwn-d307fb16f788823b29aab9aa7e4821ac8a124b19.tar.gz lwn-d307fb16f788823b29aab9aa7e4821ac8a124b19.zip | |
Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb"
This reverts commit 9e1a27ea42691429e31f158cce6fc61bc79bb2e9.
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>
Diffstat (limited to 'include/linux/virtio_ring.h')
| -rw-r--r-- | include/linux/virtio_ring.h | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index 8e50888a6d59..67e06fe18c03 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h @@ -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; |