Redmine

When generating a thumbnail for a PDF attachment, ImageMagick's convert spawns a Ghostscript (gs) process to render the PDF. If the generation exceeds thumbnails_generation_timeout, Redmine::Thumbnail.generate kills the convert process only:

rescue Timeout::Error
  Process.kill('KILL', pid)

The KILL signal is not delivered to the child gs process, so gs keeps running even after convert is gone. This can cause orphaned gs processes to accumulate on servers that receive PDFs that are slow to render.

Steps to reproduce:

1. Set thumbnails_generation_timeout in config/configuration.yml to a small value
2. Attach a PDF file that takes longer than the timeout to render (or replace gs with a script that sleeps)
3. Open a page that displays the attachment thumbnail
4. After the timeout, ps shows the gs process still running