linux-kernel - Re: [tip: core/urgent] compiler.h: Avoid the usage of __typeof_unqual__() when __GENKSYMS_

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Message-ID: <Z_wI0uNoG2G2TQMC@gmail.com>
Date: Sun, 13 Apr 2025 20:56:18 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
	Paul Menzel <pmenzel@...gen.mpg.de>, x86@...nel.org
Subject: Re: [tip: core/urgent] compiler.h: Avoid the usage of
 __typeof_unqual__() when __GENKSYMS__ is defined


* Uros Bizjak <ubizjak@...il.com> wrote:

> On Sun, Apr 13, 2025 at 10:55 AM Ingo Molnar <mingo@...nel.org> wrote:
> >
> >
> > * Uros Bizjak <ubizjak@...il.com> wrote:
> >
> > > > Yeah, agreed, I've removed this workaround from tip:core/urgent for
> > > > the time being - it's not like genksyms is some magic external
> > > > entity we have to work around, it's an in-kernel tool that can be
> > > > fixed/enhanced in scripts/genksyms/.
> > >
> > > Please note that you will disable a check that is finally able to
> > > fail the build for a whole class of very subtle percpu bugs.
> >
> > I simply zapped a commit that was applied two days ago and asked akpm
> > to resolve a regression that was introduced upstream via his tree
> > through this commit, in this merge window:
> >
> >   ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro")
> >
> > What 'disabled checks' are you talking about?
> 
> Percpu checks require TYPEOF_UNQUAL() macro, so removing
> USE_TYPEOF_UNQUAL definition

I did nothing to remove the USE_TYPEOF_UNQUAL definition, did I?

> [...] will skip the definition of __percpu_qual in 
> arch/x86/include/asm/percpu.h (please see 
> 6a367577153acd9b432a5340fb10891eeb7e10f1), and consequently __percpu 
> macro won't be defined with __seg_gs (please see 
> 6cea5ae714ba47ea4807d15903baca9857a450e6).
> 
> If this commit is removed, [...]

I did not remove commit ac053946f5c4, it's already upstream. Nor did I 
advocate for it to be reverted - I'd like it to be fixed. So you are 
barking up the wrong tree.

Thanks,

	Ingo