[PATCH 55/94] Drivers: hv: vmbus: Fix a bug in the channel callback dispatch code

From: Sam Asadi
Date: Tue Jul 15 2014 - 13:12:48 EST

From: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>

Starting with Win8, we have implemented several optimizations to improve the
scalability and performance of the VMBUS transport between the Host and the
Guest. Some of the non-performance critical services cannot leverage these
optimization since they only read and process one message at a time.
Make adjustments to the callback dispatch code to account for the way
non-performance critical drivers handle reading of the channel.

Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: sam-the-6 <asadi.samuel@xxxxxxxxx>
drivers/hv/connection.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index e84f452..ae22e3c 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -339,9 +339,13 @@ static void process_chn_event(u32 relid)

do {
- hv_begin_read(&channel->inbound);
+ if (read_state)
+ hv_begin_read(&channel->inbound);
- bytes_to_read = hv_end_read(&channel->inbound);
+ if (read_state)
+ bytes_to_read = hv_end_read(&channel->inbound);
+ else
+ bytes_to_read = 0;
} while (read_state && (bytes_to_read != 0));
} else {
pr_err("no channel callback for relid - %u\n", relid);

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