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Subject[PATCH 2/5] Drivers: hv: vmbus: unregister panic notifier on module unload
Date
From: Vitaly Kuznetsov <vkuznets@redhat.com>

Commit 96c1d0581d00f7abe033350edb021a9d947d8d81 ("Drivers: hv: vmbus: Add
support for VMBus panic notifier handler") introduced
atomic_notifier_chain_register() call on module load. We also need to call
atomic_notifier_chain_unregister() on module unload as otherwise the following
crash is observed when we bring hv_vmbus back:

[ 39.788877] BUG: unable to handle kernel paging request at ffffffffa00078a8
[ 39.788877] IP: [<ffffffff8109d63f>] notifier_call_chain+0x3f/0x80
...
[ 39.788877] Call Trace:
[ 39.788877] [<ffffffff8109de7d>] __atomic_notifier_call_chain+0x5d/0x90
...
[ 39.788877] [<ffffffff8109d788>] ? atomic_notifier_chain_register+0x38/0x70
[ 39.788877] [<ffffffff8109d767>] ? atomic_notifier_chain_register+0x17/0x70
[ 39.788877] [<ffffffffa002814f>] hv_acpi_init+0x14f/0x1000 [hv_vmbus]
[ 39.788877] [<ffffffff81002144>] do_one_initcall+0xd4/0x210

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/vmbus_drv.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 0d8d1d7..7870a90 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1108,6 +1108,10 @@ static void __exit vmbus_exit(void)
hv_synic_clockevents_cleanup();
hv_remove_vmbus_irq();
vmbus_free_channels();
+ if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &hyperv_panic_block);
+ }
bus_unregister(&hv_bus);
hv_cleanup();
for_each_online_cpu(cpu)
--
1.7.4.1


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