linux-kernel - Re: [REGRESSION] x86: support for new UV apic

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Date:	Fri, 25 Apr 2008 11:11:22 +0200
From:	Gabriel C <nix.or.die@...glemail.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Priit Laes <plaes@...es.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jack Steiner <steiner@....com>
Subject: Re: [REGRESSION] x86: support for new UV apic

Ingo Molnar wrote:
> * Priit Laes <plaes@...es.org> wrote:
> 
>> Hey,
>>
>> I am getting two following warnings (probable one per each CPU core) 
>> using the latest Linus's git:
>>
>> WARNING: at arch/x86/kernel/genapic_64.c:86 read_apic_id+0x30/0x62()
>> Modules linked in:
>> Pid: 1, comm: swapper Not tainted 2.6.25-03563-gf7288b1 #20
> 
> thanks - could you check the patch below, does it fix the warnings?

Hi Ingo ,

I got the same warning on my Core2Quad Q9300 box , your patch fixes the warning for me.


> 
> 	Ingo
> 
> --------------->
> Subject: x86: disable preemption in native_smp_prepare_cpus
> From: Ingo Molnar <mingo@...e.hu>
> Date: Fri Apr 18 11:07:10 CEST 2008
> 
> Priit Laes reported the following warning:
> 
> Call Trace:
>  [<ffffffff8022f1e1>] warn_on_slowpath+0x51/0x63
>  [<ffffffff80282e48>] sys_ioctl+0x2d/0x5d
>  [<ffffffff805185ff>] _spin_lock+0xe/0x24
>  [<ffffffff80227459>] task_rq_lock+0x3d/0x73
>  [<ffffffff805133c3>] set_cpu_sibling_map+0x336/0x350
>  [<ffffffff8021c1b8>] read_apic_id+0x30/0x62
>  [<ffffffff806d921d>] verify_local_APIC+0x90/0x138
>  [<ffffffff806d84b5>] native_smp_prepare_cpus+0x1f9/0x305
>  [<ffffffff806ce7b1>] kernel_init+0x59/0x2d9
>  [<ffffffff80518a26>] _spin_unlock_irq+0x11/0x2b
>  [<ffffffff8020bf48>] child_rip+0xa/0x12
>  [<ffffffff806ce758>] kernel_init+0x0/0x2d9
>  [<ffffffff8020bf3e>] child_rip+0x0/0x12
> 
> fix this by generally disabling preemption in native_smp_prepare_cpus().
> 
> Reported-and-bisected-by: Priit Laes <plaes@...es.org>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/smpboot.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> Index: linux-x86.q/arch/x86/kernel/smpboot.c
> ===================================================================
> --- linux-x86.q.orig/arch/x86/kernel/smpboot.c
> +++ linux-x86.q/arch/x86/kernel/smpboot.c
> @@ -1181,6 +1181,7 @@ static void __init smp_cpu_index_default
>   */
>  void __init native_smp_prepare_cpus(unsigned int max_cpus)
>  {
> +	preempt_disable();
>  	nmi_watchdog_default();
>  	smp_cpu_index_default();
>  	current_cpu_data = boot_cpu_data;
> @@ -1197,7 +1198,7 @@ void __init native_smp_prepare_cpus(unsi
>  	if (smp_sanity_check(max_cpus) < 0) {
>  		printk(KERN_INFO "SMP disabled\n");
>  		disable_smp();
> -		return;
> +		goto out;
>  	}
>  
>  	preempt_disable();
> @@ -1237,6 +1238,8 @@ void __init native_smp_prepare_cpus(unsi
>  	printk(KERN_INFO "CPU%d: ", 0);
>  	print_cpu_info(&cpu_data(0));
>  	setup_boot_clock();
> +out:
> +	preempt_enable();
>  }
>  /*
>   * Early setup to make printk work.


Regards,

Gabriel
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