[PATCH] drivers: hv: check interrupt mask before read_index

From: Jason Wang
Date: Thu Jun 20 2013 - 01:09:31 EST

This patches add a read barriers to force the driver to check the interrupt mask
before read_index. Otherwise we may lost a kick to host.

Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
drivers/hv/ring_buffer.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 791f45d..26c93cf 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -75,6 +75,8 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
if (rbi->ring_buffer->interrupt_mask)
return false;

+ /* check interrupt_mask before read_index */
+ rmb();
* This is the only case we need to signal when the
* ring transitions from being empty to non-empty.

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