Re: NFS/TCP crashes on MIPS/RBTX4927 in v4.20-rcX (bisected)
From: Atsushi Nemoto
Date: Wed Dec 05 2018 - 08:11:58 EST
Hi Geert,
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 RBTX4926 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.
---
Atsushi Nemoto