The current stable version of Redis will fail to build if the system has the v3 line of jemalloc emerged. Additionally, if jemalloc is upgraded after an emerge of the current stable Redis, the daemon will fail to start due to being unable to load a required symbol in the jemalloc library. jemalloc should either be slotted or the current stable Redis should explicitly depend on this version.
Its actually a bit worse than outlined above. The jemalloc maintainers removed our je_ prefix, so just forcing deps won't work. I don't think slotting jemalloc will happen. We already have stable 2.6 packages. Do we need to keep 2.4 in tree?
This is fixed in newer ebuilds and 2.4.x is gone. Closing.