linux-kernel - Re: [PATCH, v2] x86: Fix printk call in print_local

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Message-ID: <4A4C5638.20706@kernel.org>
Date:	Wed, 01 Jul 2009 23:39:52 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH, v2] x86: Fix printk call in print_local_apic()

Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
>>> -	printk(KERN_DEBUG "0123456789abcdef0123456789abcdef\n" KERN_DEBUG);
>>> +	printk(KERN_DEBUG "0123456789abcdef0123456789abcdef\n");
>>>  	for (i = 0; i < 8; i++) {
>>> +		char bin[33];
>>>  		v = apic_read(base + i*0x10);
>>> +
>>> +		/* Do we really want to print out LSB first? */
>> We definitely want MSB first - i'll flip around the order.
> 
> in fact i dont remember ever having relied on the bitfield nature of 
> that printout. Since this is uncommon debug code, printing the plain 
> hexa value is more than enough.
> 
> In fact we can compact it down to a single line:
> 
> 0123456701234567012345670123456701234567012345670123456701234567
> 
> instead of 4 lines of bitfields.
> 
> So i've done the patch below that looks quite a bit simpler. Mind 
> testing it, does it fix all the printout artifacts you've seen?
> 
> 	Ingo
> 
> ------------------>
>>>From ef611b322dc9a917c71f28f9498dfff0d3949779 Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <mingo@...e.hu>
> Date: Thu, 2 Jul 2009 08:26:20 +0200
> Subject: [PATCH] x86: Fix printk call in print_local_apic()
> 
> Instead of this:
> 
> [   75.690022] <7>printing local APIC contents on CPU#0/0:
> [   75.704406] ... APIC ID:      00000000 (0)
> [   75.707905] ... APIC VERSION: 00060015
> [   75.722551] ... APIC TASKPRI: 00000000 (00)
> [   75.725473] ... APIC PROCPRI: 00000000
> [   75.728592] ... APIC LDR: 00000001
> [   75.742137] ... APIC SPIV: 000001ff
> [   75.744101] ... APIC ISR field:
> [   75.746648] 0123456789abcdef0123456789abcdef
> [   75.746649] <7>00000000000000000000000000000000
> 
> Improve the code to be saner and simpler and just print out
> the bitfield in a single line using hexa values - not as a
> (rather pointless) binary bitfield.
> 
> Partially reused Linus's initial fix for this.
> 
> Reported-and-Tested-by: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> LKML-Reference: <4A4C43BC.90506@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  arch/x86/kernel/apic/io_apic.c |   25 ++++++++++---------------
>  1 files changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 4d0216f..e32e453 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -1716,25 +1716,19 @@ __apicdebuginit(void) print_IO_APIC(void)
>  	return;
>  }
>  
> -__apicdebuginit(void) print_APIC_bitfield(int base)
> +__apicdebuginit(void) print_APIC_(int base)

?


>  {
> -	unsigned int v;
>  	int i, j;
>  
> -	if (apic_verbosity == APIC_QUIET)
> +	if (apic_verbosity != APIC_QUIET)

is this one reversed?

>  		return;
>  
> -	printk(KERN_DEBUG "0123456789abcdef0123456789abcdef\n" KERN_DEBUG);
> -	for (i = 0; i < 8; i++) {
> -		v = apic_read(base + i*0x10);
> -		for (j = 0; j < 32; j++) {
> -			if (v & (1<<j))
> -				printk("1");
> -			else
> -				printk("0");
> -		}
> -		printk("\n");
> -	}
> +	printk(KERN_DEBUG);
> +
> +	for (i = 0; i < 8; i++)
> +		printk(KERN_CONT "%08x", i, apic_read(base + i*0x10));
> +
> +	printk(KERN_CONT "\n");
>  }
>  
>  __apicdebuginit(void) print_local_APIC(void *dummy)
> @@ -1745,7 +1739,8 @@ __apicdebuginit(void) print_local_APIC(void *dummy)
>  	if (apic_verbosity == APIC_QUIET)
>  		return;
>  
> -	printk("\n" KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
> +	printk(KERN_DEBUG "\n");
> +	printk(KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
>  		smp_processor_id(), hard_smp_processor_id());
>  	v = apic_read(APIC_ID);
>  	printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v, read_apic_id());

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