From: Vitaly Kuznetsov <>

To get prepared to CPU offlining support we need co change the way how we
unbind clockevent devices. As one CPU may go online/offline multiple times
we need to bind it in hv_synic_init() and unbind it in hv_synic_cleanup().
There is an additional corner case: when we unload the module completely we
need to switch to some other clockevent mechanism before stopping VMBus or
we will hang. We can't call hv_synic_cleanup() before unloading VMBus as
we won't be able to send UNLOAD request and get a response so
hv_synic_clockevents_cleanup() has to live. Luckily, we can always call
clockevents_unbind_device(), even if it wasn't bound before and there is
no issue if we call it twice.

Signed-off-by: Vitaly Kuznetsov <>
Signed-off-by: K. Y. Srinivasan <>
 drivers/hv/hv.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index a2567a4..c11393c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -575,7 +575,7 @@ void hv_synic_clockevents_cleanup(void)
        if (!(ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE))
-       for_each_online_cpu(cpu)
+       for_each_present_cpu(cpu)
                clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);
@@ -594,8 +594,10 @@ void hv_synic_cleanup(void *arg)
        /* Turn off clockevent device */
-       if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE)
+       if (ms_hyperv.features & HV_X64_MSR_SYNTIMER_AVAILABLE) {
+               clockevents_unbind_device(hv_context.clk_evt[cpu], cpu);
+       }
        rdmsrl(HV_X64_MSR_SINT0 + VMBUS_MESSAGE_SINT, shared_sint.as_uint64);

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