ruby-libs contains .so.2.1.0, but the stap tapset needs .so.2.1.6. % rpm -q ruby-libs ruby ruby-libs-2.1.6-27.fc21.x86_64 ruby-2.1.6-27.fc21.x86_64 % grep libruby.so /usr/share/systemtap/tapset/libruby.so.2.1.6.stp | head -3 * stap -L 'process("/usr/lib*\/libruby.so.2.1.6").mark("*")' process("/usr/lib*/libruby.so.2.1.6").mark("array__create") process("/usr/lib*/libruby.so.2.1.6").mark("cmethod__entry") % ls -al /usr/lib*/libruby.so.2.* lrwxrwxrwx. 1 root root 16 Apr 14 07:19 /usr/lib64/libruby.so.2.1 -> libruby.so.2.1.0 -rwxr-xr-x. 1 root root 2501320 Apr 14 07:20 /usr/lib64/libruby.so.2.1.0
Ah, this was already fixed F22+ (bug 1202232), so similar medicine applies here. Thanks for catching and reporting this issue.
ruby-2.1.6-28.fc21 has been submitted as an update for Fedora 21. https://admin.fedoraproject.org/updates/ruby-2.1.6-28.fc21
Package ruby-2.1.6-28.fc21: * should fix your issue, * was pushed to the Fedora 21 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing ruby-2.1.6-28.fc21' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2015-7635/ruby-2.1.6-28.fc21 then log in and leave karma (feedback).
ruby-2.1.6-29.fc21 has been submitted as an update for Fedora 21. https://admin.fedoraproject.org/updates/ruby-2.1.6-29.fc21
ruby-2.1.6-29.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.