How to get complete dependency list of kernel modules at runtime

Question

Is there a way to list down from command line the complete dependency list of kernel modules loaded in the kernel at runtime?

Let me clarify my question a little bit.

What I am trying to do:

1. I get a list of all loaded modules using lsmod
2. Then remove/unload currently loaded kernel modules by running a loop. I am using modprobe -r. This step fails (obviously) as some modules are in use. (I can switch to using rmmod -r, but don't want to as it is unsafe and can crash the system.)
3. Then I want to load the modules one by one again.

It is step 2 that is failing, as I cannot get all the module dependencies before using modprobe -r.

Any ideas, suggestions or comments ?

Answer 1

man lsmod: lsmod is a trivial program which nicely formats the contents of the /proc/modules, showing what kernel modules are currently loaded.

Edited: see also: depmod -n

Answer 2

To get a list of module dependencies as would be used by modprobe (i.e. this should normally be the full list, but see the answer by user502515), use

$ modprobe --show-depends <module>

Note that this command shows more information than modinfo's depends: line, as it lists dependencies recursively (i.e. dependencies of dependencies). It also takes into account alias commands in modprobe configuration files.

Tested using:

$ modprobe -V
kmod version 14

Answer 3

However lsmod o/p is sometimes incomplete. It also does not always indicate all the modules dependent on a given module.

What you see in lsmod in the "Used by" column are merely the static symbol dependencies that you can also look at using modinfo.

If however a piece of kernel code takes a reference on a module using (try_)module_get, the caller will not be recorded. References do not have an owner (moduleA could pass the pointer to moduleB, which then module_puts it..), there is nothing to record for the Used by column.