[uml-devel] Re: [uml-user] ubd=mmap problem

[Jeff Dike <jdike@addtoit.com>]

sven@darkman.de said:
> i noticed that the uml can't reboot anymore cause it hangs in an
> endless loop when unmounting the devices. all i saw was: 
> map : /proc/mm map failed, err = 9 

I take it this is reproducable?  ubd-mmap has been stable here, so there's
something about what you're doing that's sending it off the deep end.

The best way I can think to debug it is to stick printks where /proc/mm and
ubd devices get opened and closed showing what file descriptor is involved.
Apparently, the ubd driver is closing a file descriptor that UML thinks is 
a /proc/mm descriptor.

So, could you add printks for the following values in the following places -
    fd in arch/um/kernel/skas/process.c:get_mm() after the os_open_file
    mm->context.skas.mm_fd in arch/um/kernel/skas/mmu.c:destroy_context_skas()
    
    fd in arch/um/drivers/ubd_user.c:open_ubd_file() before the os_lock_file
    dev->fd and dev->cow.fd in arch/um/drivers/ubd_kern.c:ubd_close() before
their respective calls to os_close_file

Make sure that logging is set up so that printks show up in the messages file
or on the console so that you don't lose any of it.

What I think you're looking for is ubd_close closing a /proc/mm descriptor.
This would explain things going to hell when devices are being unmounted.

I'm a little suspicious of the fact that ubd_close doesn't set the descriptors
to -1 after closing them, but I don't see a bug there offhand.

				Jeff


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