linux-kernel - [PATCH 4/6] Drivers: hv: util: Make hv_poll

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Message-Id: <1493594479-25329-4-git-send-email-kys@exchange.microsoft.com>
Date:   Sun, 30 Apr 2017 16:21:17 -0700
From:   kys@...hange.microsoft.com
To:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
        olaf@...fle.de, apw@...onical.com, jasowang@...hat.com,
        leann.ogasawara@...onical.comi, marcelo.cerri@...onical.com,
        sthemmin@...rosoft.com
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 4/6] Drivers: hv: util: Make hv_poll_channel() a little more efficient

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

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@...rosoft.com>
---
 drivers/hv/hyperv_vmbus.h |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 6113e91..fa514be 100644
--- 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);
 }
 
-- 
1.7.1