Users of CIB may easily be mislead to believing that it is generally
thread safe, or at least thread safe as long as there is a single
consumer and producer. Neither is the case, which now is clearly
communicated in the API doc.
Co-authored-by: mguetschow <mikolai.guetschow@tu-dresden.de>
This patch adds calls to be able to peek at items other than just the
oldest item in a cib based FIFO. It also adds an "unsafe" peek to match
the existing "unsafe" put and get functions.
