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Message-ID: <25226905.0IHWyHSRxb@wuerfel>
Date: Mon, 01 Sep 2014 12:26 +0200
From: Arnd Bergmann <arnd@...db.de>
To: "long.wanglong" <long.wanglong@...wei.com>
Cc: linux@....linux.org.uk, santosh.shilimkar@...com,
victor.kamensky@...aro.org, nico@...aro.org,
ben.dooks@...ethink.co.uk, cov@...eaurora.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [SMP BUG?] the return value of is_smp() is bug?
On Monday 01 September 2014 18:00:58 long.wanglong wrote:
> On 2014/9/1 13:49, Wang Long wrote:
> >
> > Hi,all
> >
> > In kernel 3.17-rc2, when i set CONFIG_HAVE_SMP = y and CONFIG_SMP_ON_UP = y
> > in .config file. the secondary core can not boot.
> >
> > when i set CONFIG_HAVE_SMP = y and CONFIG_SMP_ON_UP = n in .config file,
> > the secondary core can boot.
> >
> > But this does not happen in kernel 3.10 lts kernel, Whether the
> > CONFIG_SMP_ON_UP is set yes or no ,the secondary core can boot.
> >
> > Does the meaning of CONFIG_SMP_ON_UP changed or this is a bug in kernel 3.17-rc2 ?
> >
> >
>
> hi Arnd
>
> In above two cases, i also set CONFIG_SMP = y. in addtion,
> the CONFIG_SMP_ON_UP depends on CONFIG_SMP. when set
> CONFIG_SMP_ON_UP = y, the value of CONFIG_SMP must be y.
I see.
I'm looking at the code more closely now:
> > config: set CONFIG_HAVE_SMP = y and CONFIG_SMP_ON_UP = y
> > command: # qemu-system-arm -M vexpress-a9 -smp 2 -m 128M -kernel arch/arm/boot/zImage -nographic
> > The output:
> >
> > ..........
> > is_smp() return false;
This test basically checks whether the __fixup_smp_on_up code was
run or not. This has changed in bc41b8724f24 "ARM: 7846/1: Update
SMP_ON_UP code to detect A9MPCore with 1 CPU devices", in order
to support a quirk in the Aegis platform. Can you try reverting
that commit?
Arnd
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