+ if (!pi_state->owner)
+ newtid |= FUTEX_OWNER_DIED;
+
+ /*
+ * We are here either because we stole the rtmutex from the
+ * pending owner or we are the pending owner which failed to
+ * get the rtmutex. We have to replace the pending owner TID
+ * in the user space variable. This must be atomic as we have
+ * to preserve the owner died bit here.
+ *
+ * Note: We write the user space value _before_ changing the
+ * pi_state because we can fault here. Imagine swapped out
+ * pages or a fork, which was running right before we acquired
+ * mmap_sem, that marked all the anonymous memory readonly for
+ * cow.
+ *
+ * Modifying pi_state _before_ the user space value would
+ * leave the pi_state in an inconsistent state when we fault
+ * here, because we need to drop the hash bucket lock to
+ * handle the fault. This might be observed in the PID check
+ * in lookup_pi_state.
+ */
+retry:
+ if (get_futex_value_locked(&uval, uaddr))
+ goto handle_fault;
+
+ while (1) {
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (curval == -EFAULT)
+ goto handle_fault;
+ if (curval == uval)
+ break;
+ uval = curval;
+ }
+
+ /*
+ * We fixed up user space. Now we need to fix the pi_state
+ * itself.
+ */