From: Dexuan Cui decui@microsoft.com

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 --- drivers/hv/connection.c | 8 +++++--- 1 file 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;