The ubd io thread is not really a traditional thread. Set the
parent-death signal for it to ensure that it will be killed if
the UML kernel dies unexpectedly without proper cleanup.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
---
 arch/um/drivers/ubd_kern.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 7f28ec1929dc..2b8d04e67600 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -1499,6 +1499,7 @@ int io_thread(void *arg)
 {
 	int n, count, written, res;
 
+	os_set_pdeathsig();
 	os_fix_helper_signals();
 
 	while(1){
-- 
2.34.1