+/*
+ * The futex wait op wants an explicit 32-bit address and value. If the bitmap
+ * used for the spinlock is 64-bit, cast down and pass the right 32-bit region
+ * for the in-kernel checks. The value is the copy that has already been read
+ * from the atomic op.
+ *
+ * The futex wake op interprets the value as the number of waiters to wake (up
+ * to INT_MAX), so pass that along directly.
+ */
+static inline void do_futex(int nr, unsigned long *addr, unsigned long v, int futex_flags)
+{
+ u32 *addr32 = (u32 *) addr;
+ u32 *v32 = (u32 *) &v;
+ int shift = 0;
+
+ futex_flags |= FUTEX_PRIVATE_FLAG;
+
+#if BITS_PER_LONG == 64
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ shift = (nr >= 32) ? 1 : 0;
+#else
+ shift = (nr < 32) ? 1 : 0;
+#endif
+#endif
+ if (shift) {
+ addr32 += shift;
+ v32 += shift;
+ }
+ /*
+ * The shift to determine the futex address may have cast away a
+ * literal wake count value. The value is capped to INT_MAX and thus
+ * always in the low bytes of v regardless of bit nr. Copy in the wake
+ * count to whatever 32-bit range was selected.
+ */
+ if (futex_flags == FUTEX_WAKE_PRIVATE)
+ *v32 = (u32) v;
+ futex(addr32, futex_flags, *v32, NULL, NULL, 0);
+}
+