[User-mode-linux-devel] Re: 2.3.51 panic - probable answer

[William S. <wst...@po...>]

Good morning, Jeff,

On Sun, 12 Mar 2000, William Stearns wrote:

> 	Host OS 2.3.51, rh6.2beta.  running uml-2.3.51 as root with debian
> root_fs.
> 	cd / ; ls -alR >/dev/null on first xterm.  Simultaneously
> trying to log into xterm2 and the uml console - the ls is chewing up a lot
> of cycles once the directory sectors have been loaded into ram.  On the
> console:
> 
> ...
> Debian GNU/Linux potato usermode ttys/0
> [User Mode Kernel v0.14]
> root password is "root"
> guest password is "guest"
> rootmode login:
> Password:
> Last login: Sun Mar 12 05:44:31 2000 on ttys/1
> Linux usermode 2.3.51-2um #5 Fri Mar 10 21:27:54 CST 2000 um unknown
> Kernel panic: Bogus address in segv
> ...
> 
> 	
> 	Try again, this time without "mem=20M" and "fhd1=rh6.2-root_fs" on
> the command line, i.e. just ./linux-2.3.51 .  Load up a couple of
> ls -alR >/dev/null 2>&1 &
> 's in memory (OK, 17 of them) and get another:
> Kernel panic: Bogus address in segv
> 	on the uml console, with 
>  9881 root      20   0  4124 4124  4120 R N  99.9 10.7   7:51 ./linux-2.3.51 [ls]
> 	showing up on the host OS' top.  Is there any thing I can do to
> help debug this?

	One more note; the same Kernel panic showed up when I was slowly
filling up 24M of uml memory with executing bash over and over again.  It
seems that the hard drive space shrunk (perhaps as the memory used by uml
grew?), and it seemed as if UML panic'ed right about the time, ahem, I ran
out of disk space.  OK, so it's pretty tough to even get the 200M
necessary to open up both root_fs's on a laptop.
	OK, redo the test with mem=16M - and I know I have 16M free on the
host drive that holds ~/uml .  start up multiple bash's on xterm1 and
watch the fun with the uml console.  I can almost fill up the available
16M, watching the host partition space shrink proportionately but never
get to 0, and as soon as I run the one bash that would fill it up, I get:
handle_mm_fault returned -1
Killing pid 144 because of a lack of memory
	on the console and:
...
$ bash
$ bash
$ bash
Bus error (core dumped)
$ 
	on xterm1.  Much better.

	It appears to be operator error.  Ahem - I need to remember to
have as much free hard drive space on the host partition as I want to
allocate for ram to UML.
	Could the routine that tries to allocate hard drive space for
vm_file check to see if that allocation succeeded, perhaps?
	Cheers,
	- Bill