Re: RFC: remove set_fs for m68k

Andreas Schwab
2021-08-24T08:08:51Z

On Aug 23 2021, Linus Torvalds wrote:

> On Mon, Aug 23, 2021 at 2:31 PM Michael Schmitz <schmitzmic@gmail.com> wrote:
>>
>> Hi Linus,
>>
>>
>> On 24/08/21 05:59, Linus Torvalds wrote:
>> > On Sun, Aug 22, 2021 at 12:34 PM Michael Schmitz <schmitzmic@gmail.com> wrote:
>> >> Got this overnight:
>> >>
>> >>> [536154.200000] *** FORMAT ERROR *** FORMAT=0
>> >>> [536154.210000] Current process id is 4656
>> >>> [536154.230000] BAD KERNEL TRAP: 00000000
>> >>> [536154.240000] Modules linked in: atari_scsi ne 8390p [last unloaded: atari_scsi]
>> >>> [536154.260000] PC: [<00002a8c>] resume_userspace+0x14/0x16
>> >>> [536154.270000] SR: 2208 SP: 977bd1be a2: 8009b5e8
>> >>> [536154.290000] d0: 8009b5e8 d1: cfcfcfcf d2: 00000000 d3: ffffffff
>> >>> [536154.300000] d4: 00000000 d5: 00000000 a0: 8008a108 a1: 8009b7df
>> >>> [536154.320000] Process savelog (pid: 4656, task=e49aa246)
>> >>> [536154.330000] Frame format=0
>> >>> [536154.340000] Stack from 00cc5fa4:
>> >>> [536154.340000] 02088004 3666b008 1c0eb209 007eb5e8 8006a2d0 efaec378 8004366c 61ff61ff
>> >>> [536154.340000] 8006a2d4 8006a2d2 00000000 030dfffb 0044fffa 0e000000 fffa1a00 fffa1c00
>> >>> [536154.340000] fffa1e00 fffb0e40 fffb0e80 00049b66 00000040 005f5800 00000001
>> > Strange. If I read that stack frame correctly, that seems to be an
>> > exception frame of type 0xb ("Long Bus Cycle").
>>
>> Not sure where you get the 0xb from - the frame format I see is 0.
>
> The "Frame format=0" is, afaik, the format of when the error happens.
>
> But I'm looking at what the stack contents are at the time of the
> exception, to see what actually *triggered* the error.
>
> And if I read it right, the RTE that took the format error fault had this stack:
>
> 02088004 3666b008 1c0eb209 ..
>
> and that means that it tried to return with status register 0208
> (which looks correct: supervisor bit clear), to PC 80043666 (which
> might be right - it's a similar address to the ones in A0/A1).
>
> And then the format/vector value is b008.
>
> That is, if I read it right, format 0xb, which is that "Long Bus Cycle" thing.

Right. It was a fault in stage C of the instruction pipeline (SSW =
0xb209) at 0x8006a2d2-2 (BADDR-2).

Andreas.

--
Andreas Schwab, schwab@linux-m68k.org
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