sometimes, pan of LTP can not exit normally after executing all testcases

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What steps will reproduce the problem?
1. run ltp to test the testcases in syscalls01 using the following 
commands:
export PATH=$PATH:/opt/ltp-base/testcases/bin/
/opt/ltp-base/pan/pan  -e -S -a 7415 -n 7415  -p  -f  /opt/ltp-base/
runtest/syscalls01 -l result01.log -C cmd01.failed

2. after pan has executed all testcases, sometimes, pan failed to exit and 
from minicom, I can not type any key. From PC, I can ping the mbe1500 
board.

Original issue reported on code.google.com by camelguo@gmail.com on 4 Apr 2009 at 6:51