Drivers: hv: vmbus: Use get/put_cpu() in vmbus_connect()

commit 41e270f6898e7502be9fd6920ee0a108ca259d36 upstream.

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>

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index f41901f80b6456bf12f5cf0d1c98761520a3f68d..5449fc59b7f5ed2292b0d44d26e52b6a249152f2 100644 (file)
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -74,6 +74,7 @@ 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;
 
@@ -96,9 +97,10 @@ 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;