Hi Trond, On Wed, Dec 5, 2018 at 3:47 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > On Wed, Dec 5, 2018 at 2:45 PM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Wed, 2018-12-05 at 14:41 +0100, Geert Uytterhoeven wrote: > > > 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. > > > > Can you try my linux-next branch on git.linux-nfs.org? It contains a > > fixes for a hang that results from the above commit. > > > > git pull git://git.linux-nfs.org/projects/trondmy/linux-nfs.git linux-next > > Thanks for the suggestion, but unfortunately it doesn't help. In the mean time, I tried your newer linux-next, no change. I tried several other things: - remove the packed attribute (why did you add that?), - verify (at runtime) that all accesses to fraghdr, xid, and calldir are aligned, - enable RPC_DEBUG_DATA, nothing fishy seen at first sight. Is anyone else seeing this on MIPS, or any other platform? Does mounting NFS with -o nfsvers=3,tcp work on other MIPS platforms? Thanks! 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
