My suspicion is that the vfs_read probe was not triggering sufficiently often,
causing the script to keep running (and the subsequent attempt to kill it failed).
Added an extra probe within the testcase to time out after a while.
If it doesn't work, the in-testcase timeout should be further reduced.
XXX The failure to kill the process needs further investigation. It
was possible at one point to get a hang like this in the userspace
interpreter, but I'm unsure of the reason it's happening here and now.
git://sourceware.org / systemtap.git / commit