How to convince my co-worker the linux kernel code is re-entrant?
linux, linux-kernel, multithreading, reentrancy
Solution
Search the kernel mailing list archive for "BKL". That stands for "Big Kernel Lock", which is what used to be used to prevent problems. A lot of work has been put into breaking it up into pieces, to allow reentry as long different parts of the kernel are used by different processes. Most recent mentions of "BKL" (at least that I've noticed) have basically referred to somebody trying to make his own life easy by locking more than somebody else approved of, at which point they frequently say something about "returning to the days of the BKL", or something on that order.
Problem
Yeah I know ... Some people are sometimes hard to convince of what sounds natural to the rest of us, an I need your help right now SO community (or I'll go postal soon ..) One of my co-worker is convinced the linux kernel code is not re-entrant as he reads it somewhere last time he get insterested in it, likely 7 years ago. Probably its reading was right at that time, remember that multi core architecture was not much widespread some time ago and linux project at its begining or so was not totally well writen and fully fledged with all fancy features. Today is different. It's obvious that calling the same system call from different processes running in parallel on the same architecture won't lead to undefined behavior. Linux kernel is widespread now, and known for its reability even though running on multicore architectures. That is my argument for now. But what would be yours to prove that objectively ? I was thinking to show him off some function in the linux kernel (on lxr website ) as the mutex_lock() system call. Eveything is tuned to get it work in concurrent environnement. But the code could be not that obvious for newbie (as I am). Please help me.. ;-)