+# LC_HAVE_SUNRPC_CACHE_HASH_LOCK_IS_A_SPINLOCK
+#
+# kernel 4.20 commit 1863d77f15da0addcd293a1719fa5d3ef8cde3ca
+# SUNRPC: Replace the cache_detail->hash_lock with a regular spinlock
+#
+# Now that the reader functions are all RCU protected, use a regular
+# spinlock rather than a reader/writer lock.
+#
+AC_DEFUN([LC_HAVE_SUNRPC_CACHE_HASH_LOCK_IS_A_SPINLOCK], [
+tmp_flags="$EXTRA_KCFLAGS"
+EXTRA_KCFLAGS="-Werror"
+LB_CHECK_COMPILE([if cache_detail->hash_lock is a spinlock],
+hash_lock_isa_spinlock_t, [
+ #include <linux/sunrpc/cache.h>
+],[
+ spinlock_t *lock = &(((struct cache_detail *)0)->hash_lock);
+ spin_lock(lock);
+],[
+ AC_DEFINE(HAVE_CACHE_HASH_SPINLOCK, 1,
+ [if cache_detail->hash_lock is a spinlock])
+])
+EXTRA_KCFLAGS="$tmp_flags"
+]) # LC_HAVE_SUNRPC_CACHE_HASH_LOCK_IS_A_SPINLOCK
+
+#