Probable race condition while building stable/9 on stable/10

[hiren panchasara]

On 10.0-STABLE FreeBSD 10.0-STABLE #1 r269085: Fri Jul 25 06:45:32 PDT
2014, when I tried building freshly checked out stable/9 tree:

$ MAKEOBJDIRPREFIX=/var/tmp/stable_9_j make -s -j16 buildworld
A failure has been detected in another branch of the parallel make

make[1]: stopped in /usr/home/hirenp/stable_9
--- upgrade_checks ---
*** [upgrade_checks] Error code 2

make: stopped in /usr/home/hirenp/stable_9
1 error

make: stopped in /usr/home/hirenp/stable_9
$
$
$ MAKEOBJDIRPREFIX=/var/tmp/stable_9_j make -s -j8 buildworld
A failure has been detected in another branch of the parallel make

make[1]: stopped in /usr/home/hirenp/stable_9
--- upgrade_checks ---
*** [upgrade_checks] Error code 2

make: stopped in /usr/home/hirenp/stable_9
1 error

make: stopped in /usr/home/hirenp/stable_9
$
$ MAKEOBJDIRPREFIX=/var/tmp/stable_9_j make -s -j4 buildworld
A failure has been detected in another branch of the parallel make

make[1]: stopped in /usr/home/hirenp/stable_9
--- upgrade_checks ---
*** [upgrade_checks] Error code 2

make: stopped in /usr/home/hirenp/stable_9
1 error

make: stopped in /usr/home/hirenp/stable_9
$
$ MAKEOBJDIRPREFIX=/var/tmp/stable_9_j make -s -j2 buildworld
A failure has been detected in another branch of the parallel make

make[1]: stopped in /usr/home/hirenp/stable_9
--- upgrade_checks ---
*** [upgrade_checks] Error code 2

make: stopped in /usr/home/hirenp/stable_9
1 error

make: stopped in /usr/home/hirenp/stable_9
$
$ MAKEOBJDIRPREFIX=/var/tmp/stable_9_j make -s buildworld

--------------------------------------------------------------
>>> Building an up-to-date make(1)
--------------------------------------------------------------
/usr/home/hirenp/stable_9/usr.bin/make/main.c:138:10: warning: no
previous extern declaration for non-static variable 'printGraphOnly'
      [-Wmissing-variable-declarations]
Boolean         printGraphOnly; /* -p flag */
                ^
1 warning generated.
^C
$

Built successfully without -jN.

cheers,
Hiren