Machine Freezes with SMP+APIC enabled.

Lefteris Tsintjelis lefty at
Mon Nov 17 05:47:27 PST 2003

Doug White wrote:
> On Sun, 9 Nov 2003, Lefteris Tsintjelis wrote:
> > I have been experiencing random machine freezes when using SMP (Hyper
> > threading) the past week. There are no core dumps or error messages
> > displayed anywhere. Load is very minimum.  When SMP/Hyperthreading is
> > disabled machine works with no problems at full load.
> Hm, smells like Giant deadlock.
Hi Doug,

and thank you for all the info. The motherboard of the PC decided to 
finally die on me last week so it looks like it was a hardware deadlock. 
I got it replaced and cvsup to the latest STABLE. It has been working 
very STABLE the past couple of days.

Best Regards,
Lefteris Tsintjelis

> dwhite's Form Letter on Debugging Giant Deadlocks
> If you are experiencing problems with CURRENT locking up hard, it may be
> due to a deadlock against the Giant mutex, which controls large parts of
> the kernel.  Symptoms include:
> . No response to any input
>         . System video console
>         . Network (ping)
> To debug this, you will need to set up a serial console with some special
> kernel options.  Instructions for booting with serial console are in the
> Handbook, but you will have to compile with the following kernel options:
> options DDB
> options WITNESS
> options INVARIANTS
> Make sure your serial console is capable of sending a Break signal. If
> not, use "ALT_BREAK_TO_DEBUGGER" instead of "BREAK_TO_DEBUGGER".
> Enable the serial console and boot the system. Turn on terminal logging.
> In loader, stop the boot and type "boot -v" at the OK prompt to get
> additional info during the boot process.
> Once the system is up, trigger the hang. When the system hangs, issue the
> Break signal (or if you have used ALT_BREAK_TO_DEBUGGER, press Enter ~ ^E
> b (tilde, Ctrl-E, b)).
> If you get the db> prompt, then your hang is probably due to a Giant
> deadlock. If not, then something else may be at fault.
> Once in db>, run the following two commands and capture their output using
> your terminal's logging capability:
> show locks
> tr
> Take these and the boot -v output, put them on a webpage, and send a
> message to current at carefully explaining what you did to
> trigger the hang.
> Good luck!
> >
> > Best,
> > Lefteris Tsintjelis

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