On Mon, 11 Nov 2002 21:38:13 -0600, Linas Vepstas wrote: >On Tue, Nov 12, 2002 at 02:00:14AM +0100, Ulrich Weigand was heard to remark: >> Linas Vepstas wrote: >> >Ugh. Well, that could stop the show. But since the instruction causing >this would be a problem state instruction, maybe there are fewer wacky >situations to deal with. Clearly, a store can be re-executed without >harm, even if its been partly executed before. The problem would be >with any instructions that had side effects, that would not do the same >thing the second time around, as it did the first time. I don't know >what these would be. > Actually on 390, a storage instruction MAY not necessarily be able to be re-executed without problem. You need to specify what store you are talking about. A register to storage or storage to register instruction CAN be re-executed without problem. However, 390 has storage to storage instructions, and those instructions can overlap and DO overlap. And those MAY have problems if interrupted in the middle. In fact, if you look in the Principle of Operations book for MVCL, you will find an elaborate explanation of the oops that you can get if you are overlaping a MVCL, and the instruction is interrupted (which can happen easily with an MVCL on a multi-processing system). So imagine what could happen with such an instruction when you went over a page boundary, the new page had different protection, and you tried to restart the instruction.
Lloyd
