UML kernel panic on initialization

[subashab at codeaurora.org]

On 2021-07-13 13:22, Johannes Berg wrote:
> On Sat, 2021-07-10 at 15:00 -0600, subashab at codeaurora.org wrote:
>> 
>> I have reverted the following patches (to allow for a clean revert)
>> and I don't see the panic anymore -
>> 
>> bfc58e2b98e99737409cd9f4d86a79677c5b887c
>> dc01a3b9db43abf95b801c9694980777a329e303
>> 9f0b4807a44ff81cf59421c8a86641efec586610
>> 84b2789d61156db0224724806b20110c0d34b07c
> 
> Out of those 4, the last ("separate child and...") seems actually less
> intrusive than the previous one. If you revert only the first three of
> this list, does it still happen?
> 

If only the first three reverts are applied, UML seems to hang during 
initialization-

printk: console [mc-1] enabled
EXT4-fs (ubda): mounting ext3 file system using the ext4 subsystem
EXT4-fs (ubda): mounted filesystem with ordered data mode. Opts: (null). 
Quota mode: none.
VFS: Mounted root (ext3 filesystem) readonly on device 98:0.
devtmpfs: mounted
This architecture does not have kernel memory protection.
Run /sbin/init as init process
INIT: version 2.88 booting
copy_context_skas0 - stub-parent reports error 3
INIT: cannot fork, retry..
copy_context_skas0 - stub-parent reports error 3
INIT: cannot fork, retry..
copy_context_skas0 - stub-parent reports error 3
INIT: cannot fork, retry..
random: fast init done
random: crng init done
copy_context_skas0 - stub-parent reports error 3
INIT: cannot fork, retry..
copy_context_skas0 - stub-parent reports error 3
INIT: cannot fork, retry..


> Does it still happen if you unset CONFIG_CC_OPTIMIZE_FOR_SIZE and do
> CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE instead?
> 
> johannes

If none of the reverts are applied and I set 
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE,
I still see the initialization crash.