linux-kernel - Re: [PATCH 2/2] x86 mce: use new printk recursion disabling interface

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Message-ID: <4FC2DDFF.3020600@intel.com>
Date:	Mon, 28 May 2012 10:07:59 +0800
From:	ShuoX Liu <shuox.liu@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>, andi@...stfloor.org,
	Tony Luck <tony.luck@...el.com>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 2/2] x86 mce: use new printk recursion disabling interface

On 2012年05月25日 15:41, Borislav Petkov wrote:

> On Fri, May 25, 2012 at 03:21:12PM +0800, ShuoX Liu wrote:
>> From: ShuoX Liu <shuox.liu@...el.com>
>>
>> Disable printk recursion to make sure MCE logs printed out.
>>
>> Signed-off-by: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
>> Signed-off-by: ShuoX Liu <shuox.liu@...el.com>
>> ---
>>  arch/x86/kernel/cpu/mcheck/mce.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
>> index 2afcbd2..365c35d 100644
>> --- a/arch/x86/kernel/cpu/mcheck/mce.c
>> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
>> @@ -1015,6 +1015,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
>>  	DECLARE_BITMAP(toclear, MAX_NR_BANKS);
>>  	char *msg = "Unknown";
>>  
>> +	printk_recursion_check_disable();
>>  	atomic_inc(&mce_entry);
>>  
>>  	this_cpu_inc(mce_exception_count);
>> @@ -1144,6 +1145,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
>>  	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
>>  out:
>>  	atomic_dec(&mce_entry);
>> +	printk_recursion_check_enable();
> 
> Looks like those should be at the beginning and the end of print_mce() -
> do_machine_check() could exit without printing an MCE and disabling the
> recursion check then is superfluous, methinks.

Boris,
I checked code and found some other functions in do_machine_check() also
would printk something. Such as add_taint(). So i think we'd better
place the recursion check at the beginning and the end of
do_machine_check(). Also more printks later(maybe) added will benefit
from this. Do you agree?

> 
> Thanks.
> 


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