1 files changed, 34 insertions, 31 deletions

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index a8366fe..fce27fb 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -296,44 +296,47 @@ struct vmbus_channel *relid2channel(u32 relid)
 
 /*
  * vmbus_on_event - Process a channel event notification
+ *
+ * For batched channels (default) optimize host to guest signaling
+ * by ensuring:
+ * 1. While reading the channel, we disable interrupts from host.
+ * 2. Ensure that we process all posted messages from the host
+ *    before returning from this callback.
+ * 3. Once we return, enable signaling from the host. Once this
+ *    state is set we check to see if additional packets are
+ *    available to read. In this case we repeat the process.
+ *    If this tasklet has been running for a long time
+ *    then reschedule ourselves.
  */
 void vmbus_on_event(unsigned long data)
 {
 	struct vmbus_channel *channel = (void *) data;
-	void (*callback_fn)(void *);
+	unsigned long time_limit = jiffies + 2;
 
-	/*
-	 * A channel once created is persistent even when there
-	 * is no driver handling the device. An unloading driver
-	 * sets the onchannel_callback to NULL on the same CPU
-	 * as where this interrupt is handled (in an interrupt context).
-	 * Thus, checking and invoking the driver specific callback takes
-	 * care of orderly unloading of the driver.
-	 */
-	callback_fn = READ_ONCE(channel->onchannel_callback);
-	if (unlikely(callback_fn == NULL))
-		return;
-
-	(*callback_fn)(channel->channel_callback_context);
-
-	if (channel->callback_mode == HV_CALL_BATCHED) {
-		/*
-		 * This callback reads the messages sent by the host.
-		 * We can optimize host to guest signaling by ensuring:
-		 * 1. While reading the channel, we disable interrupts from
-		 *    host.
-		 * 2. Ensure that we process all posted messages from the host
-		 *    before returning from this callback.
-		 * 3. Once we return, enable signaling from the host. Once this
-		 *    state is set we check to see if additional packets are
-		 *    available to read. In this case we repeat the process.
+	do {
+		void (*callback_fn)(void *);
+
+		/* A channel once created is persistent even when
+		 * there is no driver handling the device. An
+		 * unloading driver sets the onchannel_callback to NULL.
 		 */
-		if (hv_end_read(&channel->inbound) != 0) {
-			hv_begin_read(&channel->inbound);
+		callback_fn = READ_ONCE(channel->onchannel_callback);
+		if (unlikely(callback_fn == NULL))
+			return;
 
-			tasklet_schedule(&channel->callback_event);
-		}
-	}
+		(*callback_fn)(channel->channel_callback_context);
+
+		if (channel->callback_mode != HV_CALL_BATCHED)
+			return;
+
+		if (likely(hv_end_read(&channel->inbound) == 0))
+			return;
+
+		hv_begin_read(&channel->inbound);
+	} while (likely(time_before(jiffies, time_limit)));
+
+	/* The time limit (2 jiffies) has been reached */
+	tasklet_schedule(&channel->callback_event);
 }
 
 /*