gstack attaches to the active process named by the pid on the command line, and prints out an execution stack trace. If ELF symbols exist in the binary (usually the case unless you have run strip(1)), then symbolic addresses are printed as well.
If the process is part of a thread group, then gstack will print out a stack trace for each of the threads in the group.
Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>