linux-kernel - Re: [PATCH] preempt/hardirq.h: Fix comment about PREEMPT

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Message-ID: <502A0BB1.4030608@linux.vnet.ibm.com>
Date:	Tue, 14 Aug 2012 13:56:25 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	tglx@...utronix.de, mingo@...nel.org, paulmck@...ux.vnet.ibm.com,
	josh@...htriplett.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] preempt/hardirq.h: Fix comment about PREEMPT_ACTIVE bit
 location

On 07/31/2012 09:19 AM, Steven Rostedt wrote:
> On Sat, 2012-07-21 at 00:54 +0530, Srivatsa S. Bhat wrote:
>> PREEMPT_ACTIVE flag is bit 27, not 28. Fix the comment.
>>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>> ---
>>
>>  include/linux/hardirq.h |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
>> index bb7f309..305f23c 100644
>> --- a/include/linux/hardirq.h
>> +++ b/include/linux/hardirq.h
>> @@ -22,7 +22,7 @@
>>   *
>>   * - bits 16-25 are the hardirq count (max # of nested hardirqs: 1024)
>>   * - bit 26 is the NMI_MASK
>> - * - bit 28 is the PREEMPT_ACTIVE flag
>> + * - bit 27 is the PREEMPT_ACTIVE flag
> 
> Sorry but in arch/x86/include/asm/thread_info.h we have:
> 
> #define PREEMPT_ACTIVE		0x10000000
> 
> Which happens to be the 28th bit, not 27th. Although, if an arch did not
> define PREEMPT_ACTIVE it would be 27th.
> 
> Perhaps the correct thing to do is to say:
> 
>   By default the following bits are defined as:
> 	[...]
>   Different architectures may modify these.
> 
> And then add your change.
> 

Thanks a lot for your suggestions Steve! And sorry for the delay..
I'll post the updated patch (which applies on latest Linus master) as a reply
to this thread.

Regards,
Srivatsa S. Bhat

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