Yang Zhang, thanks for the report.  Unfortunately, it will be virtually impossible for us to try to debug this without a test case.  I see libpq.so in there, which I believe is from Postgres.  Is that correct?  There is no postgres module that's part of standard python.  The extension module is a third party extension.  It's possible that's where the problem is.  Without more info, it could really be anywhere.

Perhaps you could run this under valgrind or some other memory debugger and find the problem or at least narrow it down?