I've been getting sporadic SIGSEGV crashes in _heapqmodule.c I have not be able to reliably reproduce it, but here is a stacktrace: Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x2aaaad51d940 (LWP 13976)] (gdb) where #0 0x00002aaaab617e8a in _siftdown (heap=0xa1f2d8, startpos=0, pos=46) at [...]/Python-2.7.2/Modules/_heapqmodule.c:67 #1 0x00002aaaab617f76 in heappush (self=<value optimized out>, args=<value optimized out>) at [...]/Python-2.7.2/Modules/_heapqmodule.c:137 #2 0x000000000049ba34 in call_function (f=0xa565e0, throwflag=<value optimized out>) at Python/ceval.c:4013 #3 PyEval_EvalFrameEx (f=0xa565e0, throwflag=<value optimized out>) at Python/ceval.c:2666 #4 0x000000000049ca8d in call_function (f=0xa60f40, throwflag=<value optimized out>) at Python/ceval.c:4099 #5 PyEval_EvalFrameEx (f=0xa60f40, throwflag=<value optimized out>) at Python/ceval.c:2666 #6 0x000000000049ca8d in call_function (f=0xa5e210, throwflag=<value optimized out>) at Python/ceval.c:4099 #7 PyEval_EvalFrameEx (f=0xa5e210, throwflag=<value optimized out>) at Python/ceval.c:2666 #8 0x000000000049ca8d in call_function (f=0xa5e020, throwflag=<value optimized out>) at Python/ceval.c:4099 #9 PyEval_EvalFrameEx (f=0xa5e020, throwflag=<value optimized out>) at Python/ceval.c:2666 #10 0x000000000049ca8d in call_function (f=0xa5de00, throwflag=<value optimized out>) at Python/ceval.c:4099 #11 PyEval_EvalFrameEx (f=0xa5de00, throwflag=<value optimized out>) at Python/ceval.c:2666 #12 0x000000000049ca8d in call_function (f=0xa5dc30, throwflag=<value optimized out>) at Python/ceval.c:4099 #13 PyEval_EvalFrameEx (f=0xa5dc30, throwflag=<value optimized out>) at Python/ceval.c:2666 #14 0x000000000049d87b in PyEval_EvalCodeEx (co=0x896530, globals=<value optimized out>, locals=<value optimized out>, args=0x99dba8, argcount=1, kws=0x0, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3253 #15 0x00000000004fbf9f in function_call (func=0x8c30c8, arg=0x99db90, kw=0x0) at Objects/funcobject.c:526 #16 0x000000000041882d in PyObject_Call (func=0x8c30c8, arg=0x99db90, kw=0x0) at Objects/abstract.c:2529 #17 0x000000000041fd3f in instancemethod_call (func=<value optimized out>, arg=0x99db90, kw=0x0) at Objects/classobject.c:2578 #18 0x000000000041882d in PyObject_Call (func=0x2aaaaab7e730, arg=0x2aaaaaabc050, kw=0x0) at Objects/abstract.c:2529 #19 0x0000000000494a66 in PyEval_CallObjectWithKeywords (func=0x2aaaaab7e730, arg=0x2aaaaaabc050, kw=0x0) at Python/ceval.c:3882 #20 0x00000000004d30d2 in t_bootstrap (boot_raw=0x96d320) at ./Modules/threadmodule.c:614 #21 0x0000003fa780683d in start_thread () from /lib64/libpthread.so.0 #22 0x0000003fa6cd503d in clone () from /lib64/libc.so.6