[softirq]

This is an extremely common issue to deal with when creating a kernel, which is, again, why levels of indirection in code and hiding context only makes life more difficult for a systems developer. The kernel may need to enable accelerators, switch between arm and thumb, enable an fpu, clear cache lines, etc. A lot of decisions will be made by the compiler, but based upon parameters passed in at build time, and a lot of it will be arch specific code interwoven in assembly. And there are tons of times when a compiler will generate things you don't want, forcing you to add pragmas and so forth.