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authorRusty Russell <rusty@rustcorp.com.au>2010-02-24 15:22:22 -0500
committerRusty Russell <rusty@rustcorp.com.au>2010-02-23 22:52:24 -0500
commit97a545ab6ce922a0f868d192718a48a0091ebc5e (patch)
tree1593d2a0f0ff19c4deb731d6079997e79989c8b1 /drivers/virtio
parent28ff4ef71795fe6f6c0cc06a04911c9ca09c2c11 (diff)
virtio: remove bogus barriers from DEBUG version of virtio_ring.c
With DEBUG defined, we add an ->in_use flag to detect if the caller invokes two virtio methods in parallel. The barriers attempt to ensure timely update of the ->in_use flag. But they're voodoo: if we need these barriers it implies that the calling code doesn't have sufficient synchronization to ensure the code paths aren't invoked at the same time anyway, and we want to detect it. Also, adding barriers changes timing, so turning on debug has more chance of hiding real problems. Thanks to MST for drawing my attention to this code... CC: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_ring.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index fbd2ecde93e4..1ee97d402a48 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -36,10 +36,9 @@
36 panic("%s:in_use = %i\n", \ 36 panic("%s:in_use = %i\n", \
37 (_vq)->vq.name, (_vq)->in_use); \ 37 (_vq)->vq.name, (_vq)->in_use); \
38 (_vq)->in_use = __LINE__; \ 38 (_vq)->in_use = __LINE__; \
39 mb(); \
40 } while (0) 39 } while (0)
41#define END_USE(_vq) \ 40#define END_USE(_vq) \
42 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0) 41 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
43#else 42#else
44#define BAD_RING(_vq, fmt, args...) \ 43#define BAD_RING(_vq, fmt, args...) \
45 do { \ 44 do { \