Hi Nemoto-san, On Wed, Dec 5, 2018 at 2:11 PM Atsushi Nemoto <anemo@xxxxxxxxxxxxx> wrote: > On Tue, 4 Dec 2018 14:53:07 +0100, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > I found similar crashes in a report from 2006, but of course the code > > has changed too much to apply the solution proposed there > > (https://www.linux-mips.org/archives/linux-mips/2006-09/msg00169.html). > > > > Userland is Debian 8 (the last release supporting "old" MIPS). > > My kernel is based on v4.20.0-rc5, but the issue happens with v4.20-rc1, > > too. > > > > However, I noticed it works in v4.19! Hence I've bisected this, to commit > > 277e4ab7d530bf28 ("SUNRPC: Simplify TCP receive code by switching to using > > iterators"). > > > > Dropping the ",tcp" part from the nfsroot parameter also fixes the issue. > > > > Given RBTX4927 is little endian, just like my arm/arm64 boards, it's probably > > not an endianness issue. Sparse didn't show anything suspicious before/after > > the guilty commit. > > > > Do you have a clue? > > If it was a cache issue, disabling i-cache or d-cache completely might > help understanding the problem. I added TXx9 specific "icdisable" and > "dcdisable" kernel options for debugging long ago. > > I hope these options still works correctly with recent kernel but not > sure. > > Also, disabling i-cache makes your board VERY slow, of course. Thanks! When using these options, I do see a slowdown in early boot, but the issue is still there. My next guess is an unaligned access not using {get,put}_unaligned(), which doesn't seem to work on tx4927, but doesn't cause an exception neither. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
