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Date:   Sat, 04 Nov 2017 06:41:29 +0800
From:   "Yang Shi" <yang.s@...baba-inc.com>
To:     Joe Perches <joe@...ches.com>, apw@...onical.com,
        Jonathan Corbet <corbet@....net>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] scripts: checkpatch.pl: remove obsolete in_atomic
 rule



On 11/3/17 12:41 PM, Joe Perches wrote:
> On Sat, 2017-11-04 at 03:08 +0800, Yang Shi wrote:
>> checkpatch.pl still reports the below in_atomic warning:
>>
>> WARNING: use of in_atomic() is incorrect outside core kernel code
>> +       if (in_atomic())
>>
>> But, in_atomic() has been used outside kernel dir for a long time, and
>> even drivers. So, remove the obsolete rule even though they can be
>> ignored.
> 
> Removing in_atomic() from checkpatch does not make sense
> without also updating include/linux/preempt.h
> 
> Jonathon Corbet added this comment in
> 
> commit 8c703d35fa91911dd92a18c31a718853f483ad80
> Author: Jonathan Corbet <corbet@....net>
> Date:   Fri Mar 28 14:15:49 2008 -0700
> 
>      in_atomic(): document why it is unsuitable for general use
>      
>      Discourage people from inappropriately using in_atomic()
>      
>      Signed-off-by: Jonathan Corbet <corbet@....net>
>      Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>      Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> ---
>   include/linux/hardirq.h | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
> index 49829988bfa0..897f723bd222 100644
> --- a/include/linux/hardirq.h
> +++ b/include/linux/hardirq.h
> @@ -72,6 +72,13 @@
>   #define in_softirq()           (softirq_count())
>   #define in_interrupt()         (irq_count())
>   
> +/*
> + * Are we running in atomic context?  WARNING: this macro cannot
> + * always detect atomic context; in particular, it cannot know about
> + * held spinlocks in non-preemptible kernels.  Thus it should not be

This part looks changed. CONFIG_PREEMPT_COUNT might be enabled with 
non-preemptible kernel, so that in_atomic() could know if kernel held 
spinlocks or not.

Yang


> + * used in the general case to determine whether sleeping is possible.
> + * Do not use in_atomic() in driver code.
> + */
> 
> Maybe he remembers why...
> 
>> Signed-off-by: Yang Shi <yang.s@...baba-inc.com>
>> CC: Andrew Morton <akpm@...ux-foundation.org>
>> ---
>> Not sure if removing the obsolete rule is preferred by checkpatch.pl, anyway
>> it sounds not make sense to keep invalid rule.
>>
>>   scripts/checkpatch.pl | 11 -----------
>>   1 file changed, 11 deletions(-)
>>
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>> index 8b80bac..e8cf94f 100755
>> --- a/scripts/checkpatch.pl
>> +++ b/scripts/checkpatch.pl
>> @@ -6231,17 +6231,6 @@ sub process {
>>   			     "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
>>   		}
>>   
>> -# whine mightly about in_atomic
>> -		if ($line =~ /\bin_atomic\s*\(/) {
>> -			if ($realfile =~ m@...ivers/@) {
>> -				ERROR("IN_ATOMIC",
>> -				      "do not use in_atomic in drivers\n" . $herecurr);
>> -			} elsif ($realfile !~ m@...rnel/@) {
>> -				WARN("IN_ATOMIC",
>> -				     "use of in_atomic() is incorrect outside core kernel code\n" . $herecurr);
>> -			}
>> -		}
>> -
>>   # whine about ACCESS_ONCE
>>   		if ($^V && $^V ge 5.10.0 &&
>>   		    $line =~ /\bACCESS_ONCE\s*$balanced_parens\s*(=(?!=))?\s*($FuncArg)?/) {

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