#ifdef __KERNEL__
-/* Should never be seen by user programs */
+/*
+ * These should never be seen by user programs. To return one of ERESTART*
+ * codes, signal_pending() MUST be set. Note that ptrace can observe these
+ * at syscall exit tracing, but they will never be left for the debugged user
+ * process to see.
+ */
#define ERESTARTSYS 512
#define ERESTARTNOINTR 513
#define ERESTARTNOHAND 514 /* restart if no handler.. */