The ElectricFence RPM is not compiled with the thread safe flags.  In the
ElectricFence-2.2.2 Makefile, there is a line:

CFLAGS= -g -DUSE_SEMAPHORE $(PIC)

which sets up semaphore usage to make the ElectricFence malloc/free safe
when linked into a multithreaded application.  The problem is that the make
in the %build section of the ElectricFence.spec file overrides CFLAGS and
therefore unsets the USE_SEMAPHORE define.

I changed the Makefile to use EXTRA_CFLAGS instead of CFLAGS and changed
the tstheap:, eftest:, and .c.o: compile commands to run:

$(CC) $(CFLAGS) $(EXTRA_CFLAGS) etc.

and rebuilt the RPM.  I can now debug multithreaded application with
ElectricFence no problem.