Re: [uml-devel] WARNING: CPU: 0 PID: 908 at include/linux/thread_info.h:128 sigsuspend+0xab/0xc0()

[Vegard Nossum <vegard.nossum@oracle.com>]

On 11/16/2015 06:32 PM, Richard Weinberger wrote:
> Am 16.11.2015 um 12:49 schrieb Vegard Nossum:
>> On 11/16/2015 12:44 PM, Richard Weinberger wrote:
>>> Am 16.11.2015 um 10:43 schrieb Vegard Nossum:
>>>> Starting UML like this:
>>>>
>>>> ./vmlinux rootfstype=hostfs rw ignore_console_loglevel con=xterm init=/bin/bash
>>>>
>>>> Results in unpredictable behaviour, most of the time an xterm flashes on
>>>> my screen but the process aborts with only "Aborted" on the console
>>>> where I ran the command, sometimes the xterm remains there but frozen,
>>>> sometimes the xterm spews this warning non-stop:
>>>
>>> Hmm, is this a new regression?
>>> I bet it only happens with con=xterm, right?
>>
>> It's the first UML kernel I compile in a few years, so I don't know if
>> it's old or new, sorry.
>>
>> Yes, only con=xterm triggers this.
>
> /me found some odd stuff.
>
> arch/um/drivers/chan_user.c tries to call sigsuspend() on the host side.
> But sadly the kernel has also a function with the same name.
> So, chan_user.c calls into the UML kernel instead of the host.
> This seems to work by accident but confuses the Linux signal logic
> and you trigger from time to time the WARN_ON().
>
>  From a quick look, the kernel sigsuspend() has no users except in the same
> object file. So we can mark it static and UML calls the real one.
>
> Does the attached patch help?
> I'm sure we need more work as this clearly never worked as expected. :-(

Perfect, with your patch xterm works every time.

(With the earlyprintk tip you gave earlier, I was also able to use
con0=pts -- con0=pty doesn't seem to find any host devices, but that's
probably expected.)

Thanks a lot!


Vegard

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