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Subject[PATCH 4.18 163/168] Drivers: hv: vmbus: Use get/put_cpu() in vmbus_connect()
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dexuan Cui <decui@microsoft.com>

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>

---
drivers/hv/connection.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -76,6 +76,7 @@ static int vmbus_negotiate_version(struc
__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(struc
* 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;

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