Drivers: hv: vmbus: Use get/put_cpu() 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 get/put_cpu().

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
call put_cpu() just here.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: stable@vger.kernel.org
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index ced041899456..f4d08c8ac7f8 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -76,6 +76,7 @@ static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
                                         __u32 version)
 {
         int ret = 0;
+        unsigned int cur_cpu;
         struct vmbus_channel_initiate_contact *msg;
         unsigned long flags;
 
@@ -118,9 +119,10 @@ static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
          * the CPU attempting to connect may not be CPU 0.
          */
         if (version >= VERSION_WIN8_1) {
-                msg->target_vcpu =
-                        hv_cpu_number_to_vp_number(smp_processor_id());
-                vmbus_connection.connect_cpu = smp_processor_id();
+                cur_cpu = get_cpu();
+                msg->target_vcpu = hv_cpu_number_to_vp_number(cur_cpu);
+                vmbus_connection.connect_cpu = cur_cpu;
+                put_cpu();
         } else {
                 msg->target_vcpu = 0;
                 vmbus_connection.connect_cpu = 0;