linux-kernel - Re: [RFC patch 10/15] x86/entry: Move irq tracing to C code

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Message-ID: <alpine.DEB.2.21.1909231227050.2003@nanos.tec.linutronix.de>
Date:   Mon, 23 Sep 2019 12:27:47 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [RFC patch 10/15] x86/entry: Move irq tracing to C code

On Mon, 23 Sep 2019, Peter Zijlstra wrote:

> On Thu, Sep 19, 2019 at 05:03:24PM +0200, Thomas Gleixner wrote:
> > To prepare for converting the exit to usermode code to the generic version,
> > move the irqflags tracing into C code.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > ---
> >  arch/x86/entry/common.c          |   10 ++++++++++
> >  arch/x86/entry/entry_32.S        |   11 +----------
> >  arch/x86/entry/entry_64.S        |   10 ++--------
> >  arch/x86/entry/entry_64_compat.S |   21 ---------------------
> >  4 files changed, 13 insertions(+), 39 deletions(-)
> > 
> > --- a/arch/x86/entry/common.c
> > +++ b/arch/x86/entry/common.c
> > @@ -102,6 +102,8 @@ static void exit_to_usermode_loop(struct
> >  	struct thread_info *ti = current_thread_info();
> >  	u32 cached_flags;
> >  
> > +	trace_hardirqs_off();
> 
> Bah.. so this gets called from:
> 
>  - C code, with IRQs disabled
>  - entry_64.S:error_exit
>  - entry_32.S:resume_userspace
> 
> The first obviously doesn't need this annotation, but this patch doesn't
> remove the TRACE_IRQS_OFF from entry_64.S and only the 32bit case is
> changed.
> 
> Is that entry_64.S case an oversight, or do we need an extensive comment
> on this one?

Lemme stare at that again. At some point I probably lost track in that maze.

Thanks,

	tglx