linux-kernel - Re: [PATCH]gx-suspmod.c use boot_cpu_data instead of current_cpu

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Message-ID: <20070726164654.GC32159@redhat.com>
Date:	Thu, 26 Jul 2007 12:46:54 -0400
From:	Dave Jones <davej@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dave Young <hidave.darkstar@...il.com>,
	linux-kernel@...r.kernel.org, Dave Jones <davej@...emonkey.org.uk>,
	cpufreq@....linux.org.uk
Subject: Re: [PATCH]gx-suspmod.c use boot_cpu_data instead of
	current_cpu_data

On Wed, Jul 25, 2007 at 09:26:38PM -0700, Andrew Morton wrote:
 > On Thu, 26 Jul 2007 04:20:10 +0000 "Dave Young" <hidave.darkstar@...il.com> wrote:
 > 
 > > >On 7/25/07, Andrew Morton <akpm@...ux-foundation.org> wrote:
 > > > On Wed, 25 Jul 2007 14:19:05 +0000 Dave Young <hidave.darkstar@...il.com> wrote:
 > > >
 > > > > Hi,
 > > > > in preemptible kernel will report BUG: using smp_processor_id() in preemptible, so use boot_cpu_data instead of current_cpu_data.
 > > > >
 > > > > Signed-off-by: Dave Young <hidave.darkstar@...il.com>
 > > > >
 > > > > ---
 > > > > arch/i386/kernel/cpu/cpufreq/gx-suspmod.c |    4 ++--
 > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
 > > > >
 > > > > diff -pur linux/arch/i386/kernel/cpu/cpufreq/gx-suspmod.c linux.new/arch/i386/kernel/cpu/cpufreq/gx-suspmod.c
 > > > > --- linux/arch/i386/kernel/cpu/cpufreq/gx-suspmod.c   2007-07-25 14:11:06.000000000 +0000
 > > > > +++ linux.new/arch/i386/kernel/cpu/cpufreq/gx-suspmod.c       2007-07-25 13:57:29.000000000 +0000
 > > > > @@ -181,8 +181,8 @@ static __init struct pci_dev *gx_detect_
 > > > >       struct pci_dev *gx_pci = NULL;
 > > > >
 > > > >       /* check if CPU is a MediaGX or a Geode. */
 > > > > -     if ((current_cpu_data.x86_vendor != X86_VENDOR_NSC) &&
 > > > > -         (current_cpu_data.x86_vendor != X86_VENDOR_CYRIX)) {
 > > > > +     if ((boot_cpu_data.x86_vendor != X86_VENDOR_NSC) &&
 > > > > +         (boot_cpu_data.x86_vendor != X86_VENDOR_CYRIX)) {
 > > > >               dprintk("error: no MediaGX/Geode processor found!\n");
 > > > >               return NULL;
 > > > >       }
 > > >
 > > > um, I suspect it really wants to get at the current CPU.  But putting a
 > > > preempt_disable() around just that code is meaningless: the current CPU
 > > > could change immediately before or after the code block. It needs deeper
 > > > fixing, methinks.
 > > The only target is to get the cpu vendor, so boot_cpu_data is enough,
 > > the drivers/mtd/nand/cs553x_nand.c has the same usage.
 > 
 > I think there's some vague ambition in there to support non-identical CPUs.
 > In which case reading from the local CPU would make more sense.  (waves
 > frantically at cpufreq developers).

a non-identical CPU system with a geode + something else doesn't exist
and is very unlikely to happen.

	Dave

-- 
http://www.codemonkey.org.uk
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