Re: [BISECTED][REGRESSION] 5.10.56 longterm kernel breakage on m68k/aranym

[Finn Thain]

On Sat, 7 Aug 2021, Mikael Pettersson wrote:

> I updated the 5.10 longterm kernel on one of my m68k/aranym VMs from
> 5.10.47 to 5.10.56, and the new kernel failed to boot:
> 
> ARAnyM 1.1.0
> Using config file: 'aranym1.headless.config'
> Could not open joystick 0
> ARAnyM RTC Timer: /dev/rtc: Permission denied
> ARAnyM LILO: Error loading ramdisk 'root.bin'
> Blitter tried to read byte from register ff8a00 at 0077ee
> 
> At this point it kept running, but produced no output to the console,
> and would never get to the point of starting user-space. Attaching gdb
> to aranym showed nothing interesting, i.e. it seemed to be executing
> normally.
> 
> A git bisect identified the following commit between 5.10.52 and
> 5.10.53 as the culprit:
> # first bad commit: [9e1cf2d1ed37c934c9935f2c0b2f8b15d9355654]
> mm/userfaultfd: fix uffd-wp special cases for fork()
> 

That commit appeared in mainline between v5.13 and v5.14-rc1. Is mainline 
also affected? e.g. v5.14-rc4.

> 5.10.52, 5.11.22, 5.12.19, and 5.13.8 all boot fine. 5.10.53 to
> 5.10.56 all fail as described above.
> 
> grep ^CONFIG .config below, everything omitted is of course disabled,
> including I might add CONFIG_USERFAULTFD.
> 
> /Mikael
>