Re: [PATCH] Revert "nios2: Convert __pte_free_tlb() to use ptdescs"

[Guenter Roeck]

On 6/27/23 16:23, Guenter Roeck wrote:
> On 6/27/23 15:35, Linus Torvalds wrote:
> > On Tue, 27 Jun 2023 at 15:14, Dinh Nguyen <dinguyen@xxxxxxxxxx> wrote:
> > > This reverts commit 6ebe94baa2b9ddf3ccbb7f94df6ab26234532734.
> > >
> > > The patch "nios2: Convert __pte_free_tlb() to use ptdescs" was supposed
> > > to go together with a patchset that Vishal Moola had planned taking it
> > > through the mm tree. By just having this patch, all NIOS2 builds are
> > > broken.
> >
> > This is now at least the third time just this merge window where some
> > base tree was broken, and people thought that linux-next is some kind
> > of testing ground for it all.
> >
> > NO!
> >
> > Linux-next is indeed for testing, and for finding situations where
> > there are interactions between different trees.
> >
> > But linux-next is *not* a replacement for "this tree has to work on
> > its own". THAT testing needs to be done independently, and *before* a
> > tree hits linux-next.
> >
> > It is *NOT* ok to say "this will work in combination with that other
> > tree". EVERY SINGLE TREE needs to work on its own, because otherwise
> > you cannot bisect the end result sanely.
> >
> > We apparently had the NIOS2 tree being broken. And the RCU tree was
> > broken. And the KUnit tree was broken.
>
> Actually, this one is broken in linux-next as well because it was pulled
> into it, but the context patches needed to make it work (compile) are not
> there. It is also broken in next/pending-fixes for the same reason.
>
> Only this happened so quick that by the time I noticed and reported
> and argued that, no, I did not try to apply this patch on its own,
> the pull request into mainline was already sent and applied.
>
> Problem with linux-next is that it is so badly broken that it would take
> a full-time position to track down all its failures. Then there are those
> last-minute patches added in the week (or days) before the commit window
> opens which break it again. This is one example, but there is at least
> one more in linux-next (and pending-fixes); see
> https://kerneltests.org/builders/next-sh-pending-fixes/builds/822/steps/buildcommand/logs/stdio

And now the broken (never compiled) patch made it into mainline
and breaks the sh:dreamcast_defconfig build there.

Yes, it does happen a lot that builds are temporarily broken in mainline
because patch series are split up among maintainers and submitted to mainline
without regard of buildability. I have learned to live with that and don't
normally report it because I know (ok, hope) it is going to be fixed
by the end of the commit window.

I personally find patch series - typically doing some cleanup - which are
not even build tested on the affected architectures much more annoying.

Guenter