linux-kernel - [PATCH] Drivers: hv: vmbus: Use raw_smp_processor_id() in vmbus

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Message-ID: <PU1P153MB01694E53D6A6192A46EA3214BF370@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Thu, 23 Aug 2018 20:30:47 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "'gregkh@...uxfoundation.org'" <gregkh@...uxfoundation.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>
CC:     "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        "'driverdev-devel@...uxdriverproject.org'" 
        <driverdev-devel@...uxdriverproject.org>,
        "'olaf@...fle.de'" <olaf@...fle.de>,
        "'apw@...onical.com'" <apw@...onical.com>,
        "'jasowang@...hat.com'" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "'marcelo.cerri@...onical.com'" <marcelo.cerri@...onical.com>
Subject: [PATCH] Drivers: hv: vmbus: Use raw_smp_processor_id() in
 vmbus_connect()


With CONFIG_DEBUG_PREEMPT=y, I always see this warning:
BUG: using smp_processor_id() in preemptible [00000000]

Fix the false warning by using raw_smp_processor_id().

Here vmbus_connect() sends a message to the host and waits for the
host's response. The host will deliver the response message and an
interrupt on CPU msg->target_vcpu, and later the interrupt handler
will wake up vmbus_connect(). vmbus_connect() doesn't really have
to run on the same cpu as CPU msg->target_vcpu, so it's safe to
use raw_smp_processor_id() here.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
Cc: stable@...r.kernel.org
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Stephen Hemminger <sthemmin@...rosoft.com>
---
 drivers/hv/connection.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index ced0418..c3b7040 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -119,8 +119,8 @@ static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
 	 */
 	if (version >= VERSION_WIN8_1) {
 		msg->target_vcpu =
-			hv_cpu_number_to_vp_number(smp_processor_id());
-		vmbus_connection.connect_cpu = smp_processor_id();
+			hv_cpu_number_to_vp_number(raw_smp_processor_id());
+		vmbus_connection.connect_cpu = raw_smp_processor_id();
 	} else {
 		msg->target_vcpu = 0;
 		vmbus_connection.connect_cpu = 0;
-- 
2.7.4