Re: [PATCH v2 30/32] virtio_ring: update weak barriers to use __smp_xxx
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2016-01-01 10:22:04
Also in:
linux-arm-kernel, linux-mips, linux-s390, linux-sh, linux-um, linuxppc-dev, lkml, sparclinux
On Fri, Jan 01, 2016 at 11:39:40AM +0200, Michael S. Tsirkin wrote:
virtio ring uses smp_wmb on SMP and wmb on !SMP, the reason for the later being that it might be talking to another kernel on the same SMP machine. This is exactly what __smp_XXX barriers do, so switch to these instead of homegrown ifdef hacks. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Alexander Duyck <redacted> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The subject and commit log should say virt_xxx and not __smp_xxx - I fixed this up in my tree.
quoted hunk ↗ jump to hunk
--- include/linux/virtio_ring.h | 25 ++++--------------------- 1 file changed, 4 insertions(+), 21 deletions(-)diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h index 67e06fe..f3fa55b 100644 --- a/include/linux/virtio_ring.h +++ b/include/linux/virtio_ring.h@@ -12,7 +12,7 @@ * anyone care? * * For virtio_pci on SMP, we don't need to order with respect to MMIO - * accesses through relaxed memory I/O windows, so smp_mb() et al are + * accesses through relaxed memory I/O windows, so virt_mb() et al are * sufficient. * * For using virtio to talk to real devices (eg. other heterogeneous@@ -21,11 +21,10 @@ * actually quite cheap. */ -#ifdef CONFIG_SMP static inline void virtio_mb(bool weak_barriers) { if (weak_barriers) - smp_mb(); + virt_mb(); else mb(); }@@ -33,7 +32,7 @@ static inline void virtio_mb(bool weak_barriers) static inline void virtio_rmb(bool weak_barriers) { if (weak_barriers) - smp_rmb(); + virt_rmb(); else rmb(); }@@ -41,26 +40,10 @@ static inline void virtio_rmb(bool weak_barriers) static inline void virtio_wmb(bool weak_barriers) { if (weak_barriers) - smp_wmb(); + virt_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;-- MST