diff --git a/sys/sys/bitset.h b/sys/sys/bitset.h
--- a/sys/sys/bitset.h
+++ b/sys/sys/bitset.h
@@ -177,6 +177,10 @@
  * or a bit index.
  */
 
+#define	__BIT_ISSET_ATOMIC(_s, n, p)					\
+	((atomic_load_long(&(p)->__bits[__bitset_word(_s, n)]) &	\
+	    __bitset_mask((_s), (n))) != 0)
+
 #define	__BIT_CLR_ATOMIC(_s, n, p)					\
 	atomic_clear_long(&(p)->__bits[__bitset_word(_s, n)],		\
 	    __bitset_mask((_s), n))
@@ -259,6 +263,27 @@
 	__bit;								\
 })
 
+#define	__BIT_FFC_AT(_s, p, start) __extension__ ({			\
+	__size_t __i;							\
+	long __bit, __mask;						\
+									\
+	__mask = ~0UL << ((start) % _BITSET_BITS);			\
+	__bit = 0;							\
+	for (__i = __bitset_word((_s), (start));			\
+	    __i < __bitset_words((_s));					\
+	    __i++) {							\
+		if ((~(p)->__bits[__i] & __mask) != 0) {		\
+			__bit = ffsl(~(p)->__bits[__i] & __mask);	\
+			__bit += __i * _BITSET_BITS;			\
+			break;						\
+		}							\
+		__mask = ~0UL;						\
+	}								\
+	__bit;								\
+})
+
+#define	__BIT_FFC(_s, p) __BIT_FFC_AT((_s), (p), 0)
+
 #define	__BIT_COUNT(_s, p) __extension__ ({				\
 	__size_t __i;							\
 	long __count;							\
@@ -319,6 +344,8 @@
 #define	BIT_COPY_STORE_REL(_s, f, t)		__BIT_COPY_STORE_REL(_s, f, t)
 #define	BIT_COUNT(_s, p)			__BIT_COUNT(_s, p)
 #define	BIT_EMPTY(_s, p)			__BIT_EMPTY(_s, p)
+#define	BIT_FFC(_s, p)				__BIT_FFC(_s, p)
+#define	BIT_FFC_AT(_s, p, start)		__BIT_FFC_AT(_s, p, start)
 #define	BIT_FFS(_s, p)				__BIT_FFS(_s, p)
 #define	BIT_FFS_AT(_s, p, start)		__BIT_FFS_AT(_s, p, start)
 #define	BIT_FILL(_s, p)				__BIT_FILL(_s, p)
@@ -328,6 +355,7 @@
 #define	BIT_FOREACH_ISSET(_s, i, p)		__BIT_FOREACH_ISSET(_s, i, p)
 #define	BIT_ISFULLSET(_s, p)			__BIT_ISFULLSET(_s, p)
 #define	BIT_ISSET(_s, n, p)			__BIT_ISSET(_s, n, p)
+#define	BIT_ISSET_ATOMIC(_s, n, p)		__BIT_ISSET_ATOMIC(_s, n, p)
 #define	BIT_OR(_s, d, s)			__BIT_OR(_s, d, s)
 #define	BIT_OR2(_s, d, s1, s2)			__BIT_OR2(_s, d, s1, s2)
 #define	BIT_OR_ATOMIC(_s, d, s)			__BIT_OR_ATOMIC(_s, d, s)