[uml-devel] Problem running SMP-UML (both skas & tt)

[uml-devel] Problem running SMP-UML (both skas & tt)

[Sriram Raghunathan]

Hi,
  We're having problems running UML with SMP enabled...(ie ncpus>1) on Suse
Linux 9.0 with
2.6.5-7.97-smp (host kernel)

We've built UML with linux-2.6.11.7 & have been unsuccessful running linux
in either skas nor tt modes
for SMP. Of-course, we have absolutely no problems when we're in single cpu
mode with npcus=1.

Here I would need to mention that when we enable debug, we get the
following error message during
linking stage:
kernel/profile.c:387: undefined reference to `profile_pc".

We went ahead & commented this out to get the build to work..would
appreciate if somebody could point
 us to a patch. However this is not the crux of the problem we're facing.

Here's what happens when we try to start up UML in tt mode for
multi-cpu's...

./linux ubd0=/cics/SLES9/root.img ubd1=/cics/SLES9/swap.img umid=first
con=pty con0=fd:0,
fd:1 con1=xterm ncpus=4 mode=tt
Checking PROT_EXEC mmap in /tmp...OK
tracing thread pid = 27309

And the process just comes out...

Pl note that the linux process that we run above is built with kernel debug
enabled. (We've commented out
the reference to profile_pc)

   /*
        if (!user_mode(regs) && cpu_isset(smp_processor_id(),
prof_cpu_mask))
                profile_hit(type, (void *)profile_pc(regs));
  */

We did run with the debug option as well but did not get much out of the
gdb session..

Of-course...we would love to get the skas mode to work with SMP...but I've
read through in
many a discussion that we have issues with this. Is there a patch in place
that we could
use? Pl note that we did try with 2.6.9 with the bs7 patch but this did not
work.

We hit upon

panic("skas mode doesn't support SMP");


Here's what we see currently for skas...in linux-2.6.11.7.

umluser@lincoln:~/linux_src/src> ./linux ubd0=/cics/SLES9/root.img
ubd1=/cics/SLES9/swap.img umid=first con=pty con0=fd:0,fd:1 con1=xterm
ncpus=4
Checking for /proc/mm...found
Checking for the skas3 patch in the host...found
Checking PROT_EXEC mmap in /tmp...OK

And the process comes out.

Would appreciate if we could get any help to sort this out. If these are
know issues, perhaps a link to kernel version
 which does not have these problems(preferably skas) would be helpful.

Thanks,
Sriram







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Re: [uml-devel] Problem running SMP-UML (both skas & tt)

[Blaisorblade]

[-- Attachment #1: Type: text/plain, Size: 1280 bytes --]

On Monday 06 June 2005 15:26, Sriram Raghunathan wrote:
> Hi,
>   We're having problems running UML with SMP enabled...(ie ncpus>1) on Suse
> Linux 9.0 with
> 2.6.5-7.97-smp (host kernel)

> We've built UML with linux-2.6.11.7 & have been unsuccessful running linux
> in either skas nor tt modes
> for SMP.
Well, for SKAS mode there is no support yet... for TT mode the support used to 
work until recently, but is not very used because SKAS mode is usually 
faster, so it's less debugged than it should be...
> Of-course, we have absolutely no problems when we're in single cpu 
> mode with npcus=1.

> Here I would need to mention that when we enable debug, we get the
> following error message during
> linking stage:
> kernel/profile.c:387: undefined reference to `profile_pc".

> We went ahead & commented this out to get the build to work..would
> appreciate if somebody could point
>  us to a patch. However this is not the crux of the problem we're facing.
The fixlet for this is attached... Sadly I cannot help for now on the bigger 
picture, but I'll have a look on it.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

[-- Attachment #2: uml-add-profile-pc-i386.patch --]
[-- Type: text/x-diff, Size: 659 bytes --]



Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---


diff -puN include/asm-um/ptrace-i386.h~uml-add-profile-pc-i386 include/asm-um/ptrace-i386.h
--- clean-linux-2.6.11/include/asm-um/ptrace-i386.h~uml-add-profile-pc-i386	2005-06-06 17:57:23.000000000 +0200
+++ clean-linux-2.6.11-paolo/include/asm-um/ptrace-i386.h	2005-06-06 17:57:24.000000000 +0200
@@ -30,6 +30,10 @@
 #define PT_REGS_SYSCALL_RET(r) PT_REGS_EAX(r)
 #define PT_FIX_EXEC_STACK(sp) do ; while(0)
 
+/* Cope with a conditional i386 definition. */
+#undef profile_pc
+#define profile_pc(regs) PT_REGS_IP(regs)
+
 #define user_mode(r) UPT_IS_USER(&(r)->regs)
 
 #endif
_