port-amd64/47437: sometimes boot fails with KASSERT(pmap_tlb_pendcount < ncpu)

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

>Number:         47437
>Category:       port-amd64
>Synopsis:       sometimes boot fails with KASSERT(pmap_tlb_pendcount < ncpu)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jan 12 17:10:00 +0000 2013
>Originator:     Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
>Release:        NetBSD 6.99.16
>Organization:
>Environment:
System: NetBSD ... 6.99.16 NetBSD 6.99.16 (RIAKERN) #1: Wed Jan  9 19:58:47 UTC 
2013 
root@...:/home/riastradh/netbsd/current/obj.amd64/sys/arch/amd64/compile/RIAKERN
 amd64
Architecture: amd64
Machine: amd64
>Description:

        Sometimes when I boot a many-core machine, during autoconf I
        get a panic after the ACPI CPU devices are configured.  I've
        seen the panic several times; last night I caught it on the
        serial console for the first time with ddb and grabbed a stack
        trace.  I believe it always happens after all the acpicpuN
        devices are attached, but I'm not sure.

...
acpicpu21 at cpu21: ACPI CPU
acpicpu22 at cpu22: ACPI CPU
acpicpu23 at cpu23: ACPI CPU
panic: kernel diagnostic assertion "pmap_tlb_pendcount < ncpu" failed: file 
"/home/riastradh/netbsd/current/src/sys/arch/x86/x86/pmap_tlb.c", line 434
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff8025623d cs 8 rflags 246 cr2 0 ilevel 0 rsp 
fffffe813a5793a0
curlwp 0xfffffe887568e080 pid 0 lid 16 lowest kstack 0xfffffe813a576000
Stopped in pid 0.16 (system) at netbsd:breakpoint+0x5:  leave
db{0}> bt
breakpoint() at netbsd:breakpoint+0x5
vpanic() at netbsd:vpanic+0x1f2
kern_assert() at netbsd:kern_assert+0x48
pmap_tlb_shootnow() at netbsd:pmap_tlb_shootnow+0x394
pmap_update() at netbsd:pmap_update+0x3b
_x86_memio_unmap() at netbsd:_x86_memio_unmap+0xd2
AcpiExSystemMemorySpaceHandler() at netbsd:AcpiExSystemMemorySpaceHandler+0x245
AcpiEvAddressSpaceDispatch() at netbsd:AcpiEvAddressSpaceDispatch+0x157
AcpiExAccessRegion() at netbsd:AcpiExAccessRegion+0x30b
AcpiExFieldDatumIo() at netbsd:AcpiExFieldDatumIo+0x1b1
AcpiExWriteWithUpdateRule() at netbsd:AcpiExWriteWithUpdateRule+0x116
AcpiExInsertIntoField() at netbsd:AcpiExInsertIntoField+0x1d0
AcpiExWriteDataToField() at netbsd:AcpiExWriteDataToField+0x1be
AcpiExStoreObjectToNode() at netbsd:AcpiExStoreObjectToNode+0x277
AcpiExStore() at netbsd:AcpiExStore+0x1d0
AcpiExOpcode_1A_1T_1R() at netbsd:AcpiExOpcode_1A_1T_1R+0x238
AcpiDsExecEndOp() at netbsd:AcpiDsExecEndOp+0x22d
AcpiPsParseLoop() at netbsd:AcpiPsParseLoop+0xe9
AcpiPsParseAml() at netbsd:AcpiPsParseAml+0x27a
AcpiPsExecuteMethod() at netbsd:AcpiPsExecuteMethod+0x2af
AcpiNsEvaluate() at netbsd:AcpiNsEvaluate+0x305
AcpiEvAsynchExecuteGpeMethod() at netbsd:AcpiEvAsynchExecuteGpeMethod+0x15f
sysmon_task_queue_thread() at netbsd:sysmon_task_queue_thread+0x44
db{0}> 

>How-To-Repeat:

        Boot my many-core machine a few times.

>Fix:

        Yes, please!