Drivers: hv: vmbus: Fix a siganlling host signalling issue

[firefly-linux-kernel-4.4.55.git] / drivers / hv / channel.c

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index fddd3b5e59a9a423ec4c5aa9ce67b1c503138e2d..54da66dc7d16c033db21664606a0fe7efc576535 100644 (file)
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -611,7 +611,19 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
 
        ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
-       if ((ret == 0) && kick_q && signal)
+       /*
+        * Signalling the host is conditional on many factors:
+        * 1. The ring state changed from being empty to non-empty.
+        *    This is tracked by the variable "signal".
+        * 2. The variable kick_q tracks if more data will be placed
+        *    on the ring. We will not signal if more data is
+        *    to be placed.
+        *
+        * If we cannot write to the ring-buffer; signal the host
+        * even if we may not have written anything. This is a rare
+        * enough condition that it should not matter.
+        */
+       if (((ret == 0) && kick_q && signal) || (ret))
                vmbus_setevent(channel);
 
        return ret;
@@ -702,7 +714,19 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 
        ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
-       if ((ret == 0) && kick_q && signal)
+       /*
+        * Signalling the host is conditional on many factors:
+        * 1. The ring state changed from being empty to non-empty.
+        *    This is tracked by the variable "signal".
+        * 2. The variable kick_q tracks if more data will be placed
+        *    on the ring. We will not signal if more data is
+        *    to be placed.
+        *
+        * If we cannot write to the ring-buffer; signal the host
+        * even if we may not have written anything. This is a rare
+        * enough condition that it should not matter.
+        */
+       if (((ret == 0) && kick_q && signal) || (ret))
                vmbus_setevent(channel);
 
        return ret;