Re: [RFC PATCH] scripts: checkpatch.pl: remove obsolete in_atomic rule

[Yang Shi]

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@xxxxxxx>
> 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@xxxxxxx>
>      Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>      Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
>   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@xxxxxxxxxxxxxxx>
> > CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > ---
> > 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@^drivers/@) {
> > -				ERROR("IN_ATOMIC",
> > -				      "do not use in_atomic in drivers\n" . $herecurr);
> > -			} elsif ($realfile !~ m@^kernel/@) {
> > -				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)?/) {