ccache pausing in buildworld

[Warren Block]

About a month ago, ccache began to pause in buildworld.  The build 
doesn't halt or quit, it stays running but not doing anything:

/usr/local/libexec/ccache/world-cc -fpic -DPIC -O2 -pipe -march=prescott -I/usr/src/lib/libc/include -I/usr/src/lib/libc/../../include -I/usr/src/lib/libc/i386-DNLS -D__DBINTERFACE_PRIVATE -I/usr/src/lib/libc/../../contrib/gdtoa -DINET6 -I/usr/obj/usr/src/lib/libc -I/usr/src/lib/libc/resolv -D_ACL_PRIVATE -DPOSIX_MISTAKE -I/usr/src/lib/libc/locale -DBROKEN_DES -DPORTMAP -DDES_BUILTIN -I/usr/src/lib/libc/rpc -DYP -DNS_CACHING -DSYMBOL_VERSIONING -std=gnu99 -fstack-protector -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -Wno-pointer-sign -c crypt_xdr.c -o crypt_xdr.So

And there it stays:

   load: 0.02  cmd: make 83143 [select] 401.32r 0.05u 0.05s 0% 852k
   load: 0.01  cmd: make 83143 [select] 409.08r 0.05u 0.05s 0% 852k
   load: 0.01  cmd: make 83143 [select] 422.00r 0.05u 0.05s 0% 852k

The file where it pauses varies depending on the number of jobs (-j) 
option.  The example above is with -j6; -j1 doesn't fix it, although it 
pauses on nslexer.c instead.

This is on 8-stable as of today, i386.  The -march=prescott option comes 
from CPUTYPE?=core2 in make.conf, and removing that setting doesn't fix 
the problem.

buildworld without ccache works fine, just takes more than twice as 
long.

The kernel target works fine with or without ccache.

Any ideas?