| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 90/94] Drivers: hv: vmbus: Use get/put_cpu() in vmbus_connect() | Date | Mon, 8 Oct 2018 20:32:11 +0200 |
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4.14-stable review patch. If anyone has any objections, please let me know.
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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 @@ -74,6 +74,7 @@ static int vmbus_negotiate_version(struc __u32 version) { int ret = 0; + unsigned int cur_cpu; struct vmbus_channel_initiate_contact *msg; unsigned long flags; @@ -96,9 +97,10 @@ 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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