linux-kernel - Re: [PATCH v2] arm64: entry.S: Do not preempt from IRQ before all cpufeatures are enabled

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Message-ID: <20191016155328.exfa25uc6thdpq7b@willie-the-truck>
Date:   Wed, 16 Oct 2019 16:53:29 +0100
From:   Will Deacon <will@...nel.org>
To:     James Morse <james.morse@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Julien Thierry <julien.thierry@....com>
Subject: Re: [PATCH v2] arm64: entry.S: Do not preempt from IRQ before all
 cpufeatures are enabled

Hi James,

On Wed, Oct 16, 2019 at 10:35:13AM +0100, James Morse wrote:
> On 15/10/2019 21:07, Will Deacon wrote:
> > Patch looks good apart from one thing...
> > 
> > On Tue, Oct 15, 2019 at 06:25:44PM +0100, James Morse wrote:
> >> diff --git a/include/linux/sched.h b/include/linux/sched.h
> >> index 2c2e56bd8913..67a1d86981a9 100644
> >> --- a/include/linux/sched.h
> >> +++ b/include/linux/sched.h
> >> @@ -223,6 +223,7 @@ extern long schedule_timeout_uninterruptible(long timeout);
> >>  extern long schedule_timeout_idle(long timeout);
> >>  asmlinkage void schedule(void);
> >>  extern void schedule_preempt_disabled(void);
> >> +asmlinkage void preempt_schedule_irq(void);
> > 
> > I don't understand the need for this hunk, since we're only calling the
> > function from C now. Please could you explain?
> 
> (A prototype is needed to make the thing build[0], but)

Got it, thanks. I'm surprised the prototype doesn't exist already, but it
looks like we'll be the first C caller.

I'll queue this as a fix.

Will