Commit 41e270f6 authored Sep 17, 2018 by Dexuan Cui Committed by Greg Kroah-Hartman Sep 30, 2018

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>

parent 17b57b18

drivers/hv/connection.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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;

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