Re: [PATCH 3/4] rhashtable: use bit_spin_locks to protect hash bucket.

[Guenter Roeck]

On 4/10/19 11:40 PM, NeilBrown wrote:
> On Thu, Apr 11 2019, NeilBrown wrote:
>
> > On Thu, Apr 11 2019, NeilBrown wrote:
> >
> > > On Wed, Apr 10 2019, Guenter Roeck wrote:
> > >
> > > > Hi,
> > .....
> > > > This patch causes my qemu q800 boot test to crash reliably.
> > ....
> > > > Code: 4a89 6604 4280 60ea 2c2b 000c 2748 000c <2869> 000c 082c 0003 0002 6728 4878 0014 7620 4873 3800 486e ffec 4eb9 002e 5b88
> > >
> > > Thanks for testing and for the report.
> > .....
> > > .... and after googling a bit I see that 68000 require 2-byte alignment,
> > > but not 4-byte.  Oh..
> > >
> > > That means there aren't two spare bits in an address, so I cannot use
> > > one for the NULLS and one for a lock bit.  Bother.
> > >
> > > I might be able to find a different way forward, but for now I think we
> > > need to drop this series.
> >
> > I have found a way forward that I like.  It only requires one bit per
> > address to be over-loaded.
> >
> > The following patch implements it and works for me.
> > Could you please confirm that it fixes your problem on m68k ??
>
> Sorry, that was on the wrong base.
>
> Please try this one, against current net-next.

First of all, excellent analysis!

With this patch applied:

Build reference: next-20190410-1-ge294005789ed

Building mcf5208evb:m5208:m5208evb_defconfig:initrd ... running .... passed
Building q800:m68040:mac_defconfig:initrd ... running .... passed
Building q800:m68040:mac_defconfig:rootfs ... running .... passed


I also reconfirmed the crash with next-20190410.

With that, feel free to add:

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Thanks,
Guenter