c - Update shared libraries without restarting processes

Question

If my process is loading a .so library and if a new version of the library is available is it possible to switch to the new library without doing a process restart ? Or the answer depends on things like whether there is a parameter change to one of the existing functions in the library ?

I am working in a pretty big system which runs 100s of processes and each loading 10s of libraries. The libraries provide specific functionality and are provided by separate teams. So when one of the library changes (for a bug fix lets say) ideal thing would be to publish it under-the-hood without impacting the running process. Is it possible ?

EDIT Thanks! In my case when a new library is available all the running processes have to start using it. Its not option to let them run with the old version and pick-up the new one later. So it looks like the safer option is to just reload the processes.

Answer 1

You cannot upgrade a linked library on the fly with a process running. You could even try to, but if you succed (and you'll not fail with a "text file is in use" error message), you'll have to restart the process to make it mapping the new library into memory.

You can use lsof command to check which libraries are linked in (runtime or linktime):

lsof -p <process_pid> | grep ' mem '