SMP kernel panic: lwkt_preempt(): held and no count

Matthew Dillon dillon at
Fri Sep 5 10:15:33 PDT 2003

:I have an Intel PR440FX motherboard with two processors.
:GENERIC configuration with SMP and APIC_IO, without
:I386_CPU, I486_CPU, I586_CPU, eisa, and unused devices.
:DEBUG=-g was set.
:It was running a make -j3 buildworld and the kernel
:paniced with the message
:panic: lwkt_preempt(): help and no count
:mp_lock = 00000000; cpuid = 0; lapic_id = 00000000
:boot() called on cpu#0
:syncing disks ....
:The syncing never completed. The system had to be hard
:I have since recompiled the SMP kernel with DDB.
:I have another Dual processor system that hangs in the same way
:as discussed in the
:SMP kernel hanging at when testing 8254 interrupt delivery
:thread. It is an Intergraph system with Intel Orion chipset.
:(440GX i think). I am still working on getting
:remote debugging to that system.

    In regards to the first system, try compiling the kernel
    with DDB, INVARIANTS, and INVARIANT_SUPPORT.  When it panics
    you should drop into a ddb> prompt from which you should be
    able to get a back trace with 'trace'.

    I think that panic ('held and no count') may be a bogus
    but I need a backtrace to see what the preemption is 

					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>

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