pmcstat log reading broken?

I'm having problems converting a hwpmc capture file to a gprof
format or getting callchain information on a system runnning -current
from today - it always crashes in pmclog_read:

> pmcstat -o pmc1 -n 32768 -S instructions
> pmcstat -R pmc1 -g
Assertion failed: (ps->ps_len == 0), function pmclog_read,
file /usr/src/lib/libpmc/pmclog.c, line 494.
Abort (core dumped)

hwpmc attaches as:

hwpmc: TSC/1/64/0x20<REA>
IAP/4/48/0x3ff<INT,USR,SYS,EDG,THR,REA,WRI,INV,QUA,PRC>
IAF/3/48/0x61<INT,REA,WRI>

The CPU is an Intel i7:

CPU: Intel(R) Core(TM) i7 CPU 920 _at_ 2.67GHz (2698.78-MHz K8-class CPU)
 Origin = "GenuineIntel" Id = 0x106a5 Stepping = 5
 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=0x98e3bd<SSE3,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,SSE4.1,SSE4.2,POPCNT>
 AMD Features=0x28100800<SYSCALL,NX,RDTSCP,LM>
 AMD Features2=0x1<LAHF>
 TSC: P-state invariant
real memory = 6442450944 (6144 MB)
avail memory = 6192877568 (5905 MB)
ACPI APIC Table: <GBT GBTUACPI>
FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s) x 2 SMT threads

-- 
Bruce Cran