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

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Date:	Tue, 15 Jul 2014 20:01:10 +0300
From:	Sam Asadi <asadi.samuel@...il.com>
To:	gregkh@...uxfoundation.org
Cc:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>, <stable@...r.kernel.org>,
	sam-the-6 <asadi.samuel@...il.com>
Subject: [PATCH 55/94] Drivers: hv: vmbus: Fix a bug in the channel callback dispatch code

From: "K. Y. Srinivasan" <kys@...rosoft.com>

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@...rosoft.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: sam-the-6 <asadi.samuel@...il.com>
---
 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);
 			channel->onchannel_callback(arg);
-			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);
-- 
1.7.10.4

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