initcpu.c r199067 boot hang

I am seeing a problem on my Dell Inspiron 1520 laptop causing a boot
failure (hang) after r199067 with -CURRENT.   Kernel with 199066 works
fine.

System is amd64 running generic kernel, and no loader.conf entries.
System has latest bios update.

CPU: Intel(R) Core(TM)2 Duo CPU     T7500  _at_ 2.20GHz (2194.52-MHz K8-class CPU)
  Origin = "GenuineIntel"  Id = 0x6fa  Stepping = 10
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0xe3bd<SSE3,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM>
  AMD Features=0x20100800<SYSCALL,NX,LM>
  AMD Features2=0x1<LAHF>
  TSC: P-state invariant
real memory  = 2147483648 (2048 MB)
avail memory = 2052681728 (1957 MB)
ACPI APIC Table: <DELL   M08    >
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
FreeBSD/SMP: 1 package(s) x 2 core(s)
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1


Root FS happens to be on USB (although looking at the svn diff for
199067, I am guessing this does not make a difference)  Hang occurs
right about the time that I would expect to normally see the
following:

SMP: AP CPU #1 Launched!

This is a hard hang requiring 4 second power button push.

Please let me know if any additional details or tests would be useful.

---Dave Horn