selftests/livepatch: wait for atomic replace to occur

On some machines with a large number of CPUs there is a sizable delay
between an atomic replace occurring and when sysfs updates accordingly.
This fix uses 'loop_until' to wait for the atomic replace to unload all
previous livepatches.

Reported-by: CKI Project <[email protected]>
Closes: https://datawarehouse.cki-project.org/kcidb/tests/redhat:1413102084-x86_64-kernel_upt_28
Signed-off-by: Ryan Sullivan <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Acked-by: Joe Lawrence <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

Author: ryanbsull

tools/testing/selftests/livepatch/test-livepatch.sh

@@ -139,11 +139,8 @@ load_lp $MOD_REPLACE replace=1
 grep 'live patched' /proc/cmdline > /dev/kmsg
 grep 'live patched' /proc/meminfo > /dev/kmsg
 
-mods=(/sys/kernel/livepatch/*)
-nmods=${#mods[@]}
-if [ "$nmods" -ne 1 ]; then
-	die "Expecting only one moduled listed, found $nmods"
-fi
+loop_until 'mods=(/sys/kernel/livepatch/*); nmods=${#mods[@]}; [[ "$nmods" -eq 1 ]]' ||
+        die "Expecting only one moduled listed, found $nmods"
 
 # These modules were disabled by the atomic replace
 for mod in $MOD_LIVEPATCH3 $MOD_LIVEPATCH2 $MOD_LIVEPATCH1; do