On Sun, 10 May 2020 18:26:27 +0100, Wojciech Kudla said:
> I'd like to send a patch to arch/x86/kernel/smp.c but I'm not sure about

> 1) which branch of whose tree do I crate the patch against?
> According to MAINTAINERS:

T:      git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git

There you go.   In general, you're usually OK using either the current Linus
tree or linux-next tree.  Unless you're doing work that directly intersects
with other development, those should be quite good enough.

Linus's tree:
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

To add linux-next to that:
$ git remote add linux-next git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
$ git fetch linux-next
$ git fetch --tags linux-next
... # later on
$ git remote update

Don't use 'git pull' against linux-next, because it's rebuilt every day.
Strange and wondrous things will happen.  That also means that you
can't git bisect between (say) next-20200405 and next-20200503 (though
you can bisect between a Linus v5.7-rc3 tag and a next- tag )