linux-kernel - Re: [RFC PATCH] scripts: checkpatch.pl: remove obsolete in

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Date:   Fri, 03 Nov 2017 12:41:32 -0700
From:   Joe Perches <joe@...ches.com>
To:     Yang Shi <yang.s@...baba-inc.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 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
+ * 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)?/) {