linux-kernel - Re: [PATCH] x86: fix compile warning in io_apic

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Message-ID: <20080605123910.GA5938@sgi.com>
Date:	Thu, 5 Jun 2008 07:39:10 -0500
From:	Jack Steiner <steiner@....com>
To:	Andreas Herrmann <andreas.herrmann3@....com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: fix compile warning in io_apic_{32,64}.c

On Thu, Jun 05, 2008 at 02:05:57PM +0200, Andreas Herrmann wrote:
> Commit 05f2d12c3563dea8c81b301f9f3cf7919af23b13
> (x86: change GET_APIC_ID() from an inline function to an out-of-line function)
> 
> introduced a compile warning
> 
> arch/x86/kernel/io_apic_64.c: In function 'print_local_APIC':
> arch/x86/kernel/io_apic_64.c:1152: warning: 'v' is used uninitialized in this function
> 
> in some debug code -- which is not enabled by default.
> This patch reverts the code changes in print_local_APIC.
> 
> Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
> 
> --
> diff --git a/arch/x86/kernel/io_apic_32.c b/arch/x86/kernel/io_apic_32.c
> index a40d54f..9a3446f 100644
> --- a/arch/x86/kernel/io_apic_32.c
> +++ b/arch/x86/kernel/io_apic_32.c
> @@ -1489,8 +1489,8 @@ void /*__init*/ print_local_APIC(void * dummy)
>  
>  	printk("\n" KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
>  		smp_processor_id(), hard_smp_processor_id());
> -	printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v,
> -			GET_APIC_ID(read_apic_id()));
> +	v = apic_read(APIC_ID);
> +	printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v, GET_APIC_ID(v));
>  	v = apic_read(APIC_LVR);
>  	printk(KERN_INFO "... APIC VERSION: %08x\n", v);
>  	ver = GET_APIC_VERSION(v);
> diff --git a/arch/x86/kernel/io_apic_64.c b/arch/x86/kernel/io_apic_64.c
> index ef1a8df..59ed52c 100644
> --- a/arch/x86/kernel/io_apic_64.c
> +++ b/arch/x86/kernel/io_apic_64.c
> @@ -1077,7 +1077,8 @@ void __apicdebuginit print_local_APIC(void * dummy)
>  
>  	printk("\n" KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
>  		smp_processor_id(), hard_smp_processor_id());
> -	printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v, GET_APIC_ID(read_apic_id()));
> +	v = apic_read(APIC_ID);

I don't think this work on UV systems. Because of processor limitations, not
all of the APICID bits are contained in the hardware APIC_ID register. See
read_apic_id() in arch/x86/kernel/genapic_64.c.

I have not seen the compiler warning. What tree/options cause the error???


> +	printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v, GET_APIC_ID(v));
>  	v = apic_read(APIC_LVR);
>  	printk(KERN_INFO "... APIC VERSION: %08x\n", v);
>  	ver = GET_APIC_VERSION(v);
> 
> 
> 

--- jack
--
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