From: "K. Y. Srinivasan" <kys@microsoft.com>
Date: Sun, 30 Apr 2017 16:21:17 -0700
Patch-mainline: v4.13-rc1
Subject: Drivers: hv: util: Make hv_poll_channel() a little more efficient
Git-commit: 1e052a16eb2caf6727b594cad0744ccdfddf4254
References: fate#323887

The current code unconditionally sends an IPI. If we are running on the
correct CPU and are in interrupt level, we don't need an IPI.
Make this adjustment.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Olaf Hering <ohering@suse.de>
---
 drivers/hv/hyperv_vmbus.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -411,6 +411,10 @@ static inline void hv_poll_channel(struct vmbus_channel *channel,
 	if (!channel)
 		return;
 
+	if (in_interrupt() && (channel->target_cpu == smp_processor_id())) {
+		cb(channel);
+		return;
+	}
 	smp_call_function_single(channel->target_cpu, cb, channel, true);
 }