Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()'

From: Peter Zijlstra
Date: Tue Mar 15 2016 - 08:44:27 EST

On Tue, Mar 15, 2016 at 01:08:35PM +0100, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > On Tue, Mar 15, 2016 at 10:32:45AM +0100, Ingo Molnar wrote:
> > > 2) its naming sucks. "fetch_or()" does not really signal that it's a
> > > fundamentally atomic operation, nor what API family it belongs to.
> >
> > I disagree there, the fetch-$op naming is widely used for atomic
> > operations that return the previous value. See for example the C/C++11
> > atomic ops.
> The problem I see is that we don't really have the fetch_*() naming in the kernel
> right now, while we do have the xchg_*() naming. The latter is 'obviously' an
> atomic operation - while 'fetch' could be anything.

We don't have xchg_*() naming, we have xchg() and that's about it. And
yes, people know xchg() is an atomic op. But 'fetch (and) or' is also
atomic, it has to be, it needs to do 2 operations in 1.

Furthermore, the relevant wikipedia page is:

So the naming is widely established.