linux-kernel - Re: [PATCH 2/3] sched/preempt: include asm/current.h

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Date:   Fri, 14 Oct 2016 10:16:38 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 2/3] sched/preempt: include asm/current.h

On Fri, Oct 14, 2016 at 12:25:56AM +0100, Mark Rutland wrote:
> Hi,
> 
> On Thu, Oct 13, 2016 at 01:57:11PM +0200, Heiko Carstens wrote:
> > The generic preempt code needs to include <asm/current.h>. Otherwise
> > compilation fails if THREAD_INFO_IN_TASK is selected and the generic
> > preempt code is used:
> > 
> > ./include/linux/thread_info.h:17:54: error: 'current' undeclared (first use in this function)
> >  #define current_thread_info() ((struct thread_info *)current)
> 
> I don't think this is the right fix. Users of current_thread_info() should only
> have to include <linux/thread_info.h>, as <asm-generic/preempt.h> already does.
> 
> I have a patch [1] which has <linux/thread_info.h> include <asm/current.h> the
> THREAD_INFO_IN_TASK case (while avoiding circular includes over <asm/current.h>
> and <asm/thread_info.h> in the !THREAD_INFO_IN_TASK case).

I added that include initially to <linux/thread_info.h> too, but was afraid
of include dependency hell. So I tried the minimal version, and it worked.

However with the ifdef within your patch you make sure that nothing breaks
by accident; so I think your version is better.

> I was planning on posting an updated series with that come -rc1.

That could/should also go into 4.9, so architectures could independently
convert to THREAD_INFO_IN_TASK for the next merge window.