atomic_dec(&old_user->processes);
switch_uid_keyring(new_user);
current->user = new_user;
+
+ /*
+ * We need to synchronize with __sigqueue_alloc()
+ * doing a get_uid(p->user).. If that saw the old
+ * user value, we need to wait until it has exited
+ * its critical region before we can free the old
+ * structure.
+ */
+ smp_mb();
+ spin_unlock_wait(¤t->sighand->siglock);
+
free_uid(old_user);
suid_keys(current);
}